In Highschool I passed physics very well, but after graduating university. I started learning it on my own, that is where I realized that I didn't understand it before.
Fr. I am in highschool and i understand the real undercover meaning and what led the creator to create it. And by those mathematical thought processes I can even study it on my own !
I like to conceptualise voltage as E = -grad V, it is the gradient vector field of the electric field. This idea is often more intuitive. And I like to think about current as dQ/dt = V/R. The differential or integral forms are a beautiful mathematical description that is also accurate describing gradient fields and rates of change.
@louisrobitaille5810 those are 2 different things tho. The first denotes mass-energy equivalence, the second energy-momentum relation. 1. It states that the energy (E) of an object at rest is equal to its mass (m) multiplied by the speed of light squared (c²) This implies that mass can be converted to energy and vice versa. It specifically refers to rest energy. 2. This equation is the more general form that applies to objects that may be in motion.
@@schwobelabibalbol no that's not it E=mc² is when object is at rest which is likely not the case making p=0. Full formula is E²=(mc²)²+(pc)² Yes same thing apply about converting mass to energy on E²=(mc²)²+(pc)² formula
@@baldurstudios5637 he means m=E/c^2 is physically impossible because it presumes that the object in question has zero momentum which is kinda impossible to know or have in reality--you can only have zero momentum relative to something else, which is different
Some people have innate understanding of equations and notation, and have a “the way it is is just the way it is” type of mentality. They’re crazy smart people, but not great at teaching. I totally agree with your explanation! This is how I approach engineering fundamentals, from physical phenomenon to written notation.
@@GodVanisherNot really. In the same way 1+1=2 are just numbers and has a very intuitive understanding(one thing plus another is two things). There are intuitive ways to understand fields, derivatives, fluids, electricity...
@@next_door_rigil3270 Intuition is useless at some point. Everyday experiences do not align with how the world actually works. It’s just as wrong as common sense. Also I was rather focusing on the syntax and semantics of the language, which are arbitrarily chosen by humanity. Language can only be understood with references.
@@GodVanisher If a person can imagine physics properties or analogues to them in their daily lives, you are able understand them really well. And we can find analogues for most concepts we know. By understanding them, I mean being able to qualititavely predict future states of a system in your mind. The mathematics is an extension of that model. It is how we even got Eistein's relativity. Intuition came before mathematics. The quantum realm is more complicated but it is also possible.
I am an electrician and I make videos. I often find the problem with comments from electrical engineers is they only understand a mathematical analogy without really understanding what's going on and I think that's the point of your video.. love it I try teach electrical theory with minimal math and maximum working live voltage demos
The math is very very important to understand electricity. No offense but I find it almost impossible to believe even an undergrad EE would not understand ohms law far far past the point of this video. Understanding the math is what leads to the true understanding of how electricity works. Like you just cant have a good understanding of impedance for example without understanding complex phase.
@@YoungJackRack oh great, the academic has arrived. Also, what the fuck does "even an undergrad" mean? There are more university students that cant wipe their own ass than high school drop outs, so what exactly is your point?
@@YoungJackRack I have 200k followers and get tons of comments from EE that say the USA 240v system has 2 phases 180° out of phase. I hear them say electricity flows to ground. I hear them say a neutral carries only the imbalance because current is canceled. All of those ideas are just for math but to not reflect the actual function or installation. I have literally seen EEs comment higher volts means lower amps.. I work with EEs at a shipyard some are good some but some know very little about how to bring their math to life in the real world.
Wow this was a really new way to see these equations together! Physics is so much fun if taught properly but it's unfair we don't get to learn in a fun way:(
It is easier to memorize F=ma. To memorize a=F/m you have to remember which one is on top. You can always change F=ma to the firm that is useful for each situation. V=IR is useful you know the resistance and measure the amperage and need to determine what voltage is driving that amperage. So the form of the equations to use depends on what you not to find and what you know already.
You should do a video on why 0 Resistance is impossible.* *Edit: My knowledge of Superconductors was outdated, so some of my comments in this thread are (partially) incorrect. Yes, Superconductors with 0 resistance exist. So, instead, they have Current Density. This, as @Miyomotomusashi69 stated, is something closer to how batteries store electrons. *However* This does not disprove that in Ohm's Law I=V/R, R =\= 0. When you do not have a dedicated Resistor, you use the resistance of the wire in the circuit. More accurately, you just end up creating heat within the circuit. This is in fact how a traditional light bulb works. Superconductors follow the London Equations, which only work in quantum mechanics.
@@mistadude *near* 0 resistance on a superconductor. Remember, dividing by 0 is impossible. Mathematically and in real life. If you were to say "How many apples did you sell in x day(s)?" [Sales=Apples÷Day(s)] But, I spent 0 days selling apples... well I didn't have any sales of any apples then. There is no equation to speak of.
@@treeross this is true for conventional circuits, but superconductivity breaks this law due to the concept of cooper pairs, where the electrons are cooled enough to where they form positively charged "phonons", which are matched in a way that makes them behave as a single entity. Once enough of these phonons are formed, they condense into a ground state that allows them to move without scattering vibrations or impurities, thus creating zero resistance. Look up BCS theory for a deeper explanation.
@@Miyamotomusashi69 wouldn't the current still not exist in that case? Because current is a measure of V/R, without one value you can't use that measurement, right?
@@treeross the phonons do not behave like traditional electrons, when they are paired they are put into a quantum state and move through magnetic expulsion from the inside of the superconductor, which is how they exhibit current without voltage. Although a voltage is initially present which supplies the superconductor with electrons, once these thermal reactions occur the electrons are essentially "stored" within the superconductor, where they can flow without dissipation of energy. This is quantum mechanics, which goes beyond the realm of normal electrical circuits.
As a highschool student, my eyes really lit up when you got around to explaining the circuit example in the near end of the video. This feeling resonated with me because when I first learned this initially in 9th grade it confused the heck out of me whenever this equation V=IR popped.
What you should have retained from high school is that V=IR is the equation for OHMIC conductors. It is not a useful equation for conduction in gases or liquids. It doesn't work for metals at high currents, either, because of heating effects. THAT would have been the important lesson to remember.
@@lepidoptera9337 - Did you miss where he started his post saying he's a high school student - and that he learned this in 9th frade? So that wasn't even likely a physics class, but a physical science class. Even in high school physics, they don't normally get into that. They have a lot of material to cover. It's a survey of many topics at an introductory level - not an in-depth electrical circuits class.
Truly underrated video! Nowadays, schools are blindly teaching us these equations and telling students that "it's just like that" and expect us to memorise it. As someone who formerly struggled with physics, understanding the core reason why the equation is in a certain way with practical analogies (like what you did in the video), would make physics a lot more intuitive for many people! Please keep up this amazing content! Would love to see more physics videos from you. Would also love to see you touch on harder content (e.g. quantum mechanics, relativity) as I find that you break down these difficult concepts into digestable information!! :)
Interesting that the way you "rewrote" the equations was actually the way that we were taught in high school physics. Our teacher was a 1930s US Navy Academy graduate, so that's where he learned his physics. Your instruction brought back some memories of Mr Conger, thanks!
I’m currently taking PHYS I hear at Cornell…which, as you probably imagine, is tough as nails. Thanks for putting the world of physics into such an understandable manner!
Many people are misunderstanding the main message of the video. It's not about simply writing equations more precisely. The core idea is to emphasize the fundamental understanding behind those equations. Too often, students focus on memorizing formulas and solving problems mechanically, but this approach misses the essence of physics. Physics is not just about calculations-it's about understanding the nature of the world and the interconnectedness of its phenomena. The true purpose of studying physics lies in grasping the origins and meaning of equations, not just applying them blindly. Before committing formulas to memory, it's crucial to comprehend where they come from and why they work. I fully agree with the video’s perspective. Thank you for shedding light on this important aspect of learning practical physics!
This makes me happy because most teachers don't teach the true meaning of the formula but the values they put out, and students end up losing the true meaning of the formula of what it is really about🥰This is good to hear from someone else but myself☺
Well actually Mr. Postdoctoral Fellow, it is more properly written as I = V / ( R + jX ). Only noobs leave off the imaginary part of the complex impedance. Joking aside, it doesn't matter how the equation is arranged, it all maths out the same. I do recall years ago ignorantly thinking that if you just increase the resistance of the circuit enough then you can generate any arbitrarily high voltage, not recognizing what is driving what in the relationship. The problem with saying it has to be written as I=V/R assumes that voltage always drives current, this isn't always true. Currents can be induced via inductive action, changing magnetic fields, or by physically moving charged objects around; in these cases, the voltage is generated by the current and/or the reactive impedance. Electrical Engineering is a misnomer, it isn't the electricity that is being engineered (that part is governed by physics), it is the impedance that is engineered in order to control the VI relationship.
Even more damaging to main argument of this video: ALL real voltage sources exhibit an equivalent series resistance. Because of this, by using the well known theorems of Thevenin and Norton, any real source can be represented either as a voltage source (with a series resistance) or a current source (with a parallel resistance); they are equivalent.
The reason why in shool are used Simple Models like a gravity, 2nd Newton Law, Ohm Law or Energy of principles is only to capture initial understanding of basics. If You starts analyze the e.g. the diffrerential equations before the static understanding , this is not efficient way to understand the problems. The acceleration also can be driven (Simple example the stepper motor which driver gear and You want to observe the response of the hit for example or pressure)so this is correleted to the context but remember. Math is only approximation and You dont have 100 percentage model describes real. No, You can be close to real. A = f/m is crashed when You add relativity for example so 😊this is not proof,proof is the experiment and observation, however still with some deviation ;p
@@georgejo7905 Impedance has the unit of ohm which is SI defined as (kg*m^2)/(s*C^2). Since it has real and imaginary parts, makes you wonder which base units become imaginary? Capacitance and inductance have reciprocal units with exception of s^2 so there could be an argument that time is imaginary. This fits well considering that magnetic effects could very well be the consequence of relativistic effects on electric charge. And we all know that relativity makes time weird.
Epitome of never stop asking why instead of taking things at face value . Amazing video and i wish you could make beginner friendly videos down to highschool level physics
Well said. Something I’ve always understood intuitively, but this is a good reminder that I think I’m going to try to keep in mind more when tutoring other students.
As a qualified and experienced teacher math and physics I completely agree with you. However I teach 12 - 16 years old kids and when I'd try to explain this rather philosophical topic to them it would fly way beyond their yet incompletely developed brains. So I restrict myself to merely telling them that force can cause ao change in velocity (which I demonstrate by throwing my blackboard eraser through the classroom, so that they never forget). A somewhat similar issue rises when teaching Galileo's equations for motion. I teach the common, simplified versions (s = v.t). The students who graduate and continue with physics at highschool (it's called differently in Suriname) get the formal notations as functions. Sure enough my own son reproached me when he found out. My remedy is making clear that whatever I teach it is simplified. In the end this is true for every theory in physics (or in science in general). What teachers need to avoid is implying that we present the absolute truth. The theme that returns over and over again in my class is that reality is always more complicated than we think.
Hey ali , I 've been watching your videos for a while now and I really have to say that they inspired me to pursue electrical engineering,I was stuck at mechanical engineering and I kinda gave up but your videos really helped me remember why I liked electrical engineering in the first place and see other interesting aspects of it , I am starting this semester in electronics engineering school and I am majoring in communication engineering . Thanks to you I was able to take this choice and I can't thank you enough for this.
5:49 Kinda weird analogy. Gravitational and electric potential on punctual charges are both proportional to 1/r, but the former needs a much larger scale for it to start acting like the latter. Gravitational potential is so hard to change that we consistently assume our classical mechanics problems happen assuming it's constant. Electric potential can be modeled as non constant p easily. That's why it's recommended that You don't think about change in eP with the same arguments as the change in speed using gP.
You cross out V=IR and F=ma like you have a more fundamental understanding, and then you just re-explain the equations. You are better at marketing than engineering...
@@dariosarubbi3129 His only point was that he is not qualified as a science teacher. He does not understand physics, not even at the high school level.
@@scientificbhaiya9336 At least that's the kindergarten view of classical mechanics. It stops working as soon as I drop something because now there is an object accelerating downwards without any force whatsoever. OTOH, if I want to hold that object in place, then I have to supply a constant force upwards.
@@lepidoptera9337 Bro I think you misunderstood what a F is there. F is the Net force acting on the mass M, it is the overall force after adding resisting forces and supporting force, now here in the equation a=F/m the resistance is not friction but The Inertia itself I.e. the property of the mass to resist motion. And no object accelerates without a force, maybe you have a border aspect your saying, I’ll like to know more about it.
Well, I am in high school studying physics, and I’m quite fascinated with how everything works to the very basics… things like how acceleration can make something not in equilibrium, or how we came up with certain suvat equations and the relationships between the actual values. I feel like if I can master the fundamental knowledge then it would be a lot more interesting and easier to add to that knowledge.
Surface friction is not going to stop a ball from rolling. In fact, it *causes* it to roll rather than slide. Energy is only dissipated if the friction force is nonzero, but too weak to prevent sliding. Agree on the point made in the video though. When I teach physics, I always try to get the physics concept across, before introducing the mathematical formula.
Surface friction is sufficient for rolling on any solid surface in reality and so is irrelevant to discuss in his example it is more so governed by the shape of moving object instead of the surface friction, a ball(anything mostly round) will roll on any surface. Sliding of a ball can occur as you point out, simply due to a proportion of liquid/fluid state being present in the contact surface, none obvious in the example above. The reason a partial liquid phase causes translation/sliding is like sliding of a ball on normal slippery ice. This is due to the ice being partially a liquid on its surface, hence the ball will partially react to the contact as sliding and partially react as rolling. Surface friction would only affect an object that's shaped with a larger surface area touching the ground, because that would be an object that could actually slide with low friction, something like a cube instead of inherently needing to roll like a ball... The shape determines if an object will roll on a given surface, unless you say there is no surface friction in a solid-solid contact, impossible. By stating the object is a ball means it must roll. p.s. realistically there is always surface friction as I'm sure you know, this will indeed stop the ball from rolling over time by converting kinetic energy into heat, just because it isn't sliding doesn't mean there isn't heat created with every turn of the ball...
This stuff is so complicated it seems like every physics video I’ve ever watched no matter the creator always has a comment like this that’s like my goodness it’s just so much lol
Dude it's amazing.. please keep it up. Initially i thought i should skip this bcz i know all about therse 2 equations but still i watched and it blew my mind.
I thought of this a while ago and will add: Even better, I = GV, where G is called _conductance._ Likewise while there is no usual symbol for it, we might say that a = ɯF, where ɯ is the reciprocal of mass - we might call it "susceptibility to force". So the interesting question is: from this perspective, why do ɯ satisfy 1/(ɯ_tot) = 1/(ɯ_1) + 1/(ɯ_2) when we combine objects together? Hmm...
Bingo! If someone would have explained things in the way you did in this video during my younger years, I would probably have gone on to study for a PhD instead of settling for a BSc. An excellent insight!
4:53 ma=f There is a more general formulation of Newton's second law, dp/dt=f, which states that the only cause of change in motion is interaction with other objects. The quantity of motion in this law is called momentum, p, and the force, f, is a measure of the interaction between objects.
@@엉덩이먹는사람 As i understand then they are the same in that both sides of the equation are equal in all three of your examples, but he never claimed that this is untrue. His point was that it is useful to think of the right side of the equation as the cause and the left side as the effect and therefore write it as I = V / R, because V and R are the parts we control and I derives from them.
Good video, I think this was very insightful. The V=IR or I=V/R equation is just a way to show how those three variables are related. If you have 0 potential difference, you will have 0 current, and likewise if you have 0 current through some circuit element, you will have 0 voltage drop. If you have 0 resistance, you will have a very large amount of current. I feel like developing an intuitive understanding is important for this equation. What are your thoughts on using water pipes as an analogy for current, voltage and resistance?
Well, you are right 90% F=ma is also correct way in a physical pov if... We were calculating the force that the ball exerts on the second floor due to being accelerated, so here the force is a function of acceleration, while in your example the acceleration is a function of the gravity force ((external force causing the acceleration)) but it is not the only force, the ball will also exert force which is proportional to a, so in that case F=ma is more ""correct""
Your idea that equations should be written with the causal quantities on the RHS and effect-quantity as the subject on the LHS is an interesting and compelling idea. I guess, as a mathematician, I find equations involving just multiplication more "simplified" and "elegant" than the rearranged versions involving division - but from a teaching perspective (especially at, say, high-school level), your point might be stronger. Regarding voltage and current, one of the things that confused me in school is learning about setups in which it's the supplied _power_ (rather than the resistance of the circuit to which the power is being supplied) that is externally predetermined, so that one has freedom to control the supplied current or supplied voltage within the constraint of their being _inversely_ proportional to each other, rather than directly proportional as in Ohm's Law. Regarding F=ma, what's interesting is that, conceptually, it's forces that cause changes in velocity, but mathematically, the infinitesimal calculus places the change of velocity as simultaneous with (rather than temporally subsequent to) the force. This can lead to bizarre paradoxes like Norton's Dome, where one can define a dome shape [where there is a well-defined unique tangent plane to every point on the dome, and this tangent plane varies continuously with respect to the point on the dome] such that it's perfectly consistent with Newtonian mechanics for a point particle at the exact top point of the dome to stay at this top point for an arbitrary duration of time before spontaneously starting to slide down the dome. In effect, because of how infinitesimal calculus works, "F=ma" theoretically allows the 'a' to be the cause of the 'F', even though in practice it's the 'F' that is the cause of the 'a'.
If an object with mass m is accelerated because of the curvature of space, then it has a force caused by acceleration. In this case, force is the output, and acceleration is the input. Or, force is the effect, and acceleration is the cause. This is a case which directly contradicts your point. If I am wrong, please respond with a detailed explaination on why I am wrong. You are more educated than me.
I just got an example against "V=IR" : why is highest voltage ever produced about 25.5MV? Why can't we easily reach voltage in billions or trillions of volts, if all we have to do is increase the R? Then, we can proceed with what you said about causality and now it makes sense!
The Resistance doesnt depend on Current intensity or even the Voltage Resistance of a material depend on Specific Resistivity of it It's length It's area If you increase resistance You decrease the current flowing through So the product of resistance and current is always equal to the volt of the source If you want higher voltage We need a stronger Source So I Depends on V and R V doesnt depend on R or I R depends on the material and its other properties So increasing Resistance makes current decrease by an amount that always the Current.Resistance equals the Voltage of the source That's why when you get introduced to electrical engineering of circuits You always have that noted R doesnt depend on either of them Voltage is dependant on the source of it And also If you want to achieve higher voltage By higher resistance V=ir is correct We have 3 factors We want to increase v by increasing R right? You can but then you have to control i at constant value.but as we know R affects current to be Lower When YOU HAVE THE SAME VOLTAGE..
@@ahmedalaa7216 Good breakdown, thank you! Like they say, proper understanding is the key to success. I hope that education will be going more and more into properly explaining and visualizing certain concepts, as many people oftentimes don't properly understand what they are calculating, integrating, why we solve this or that equation, etc. And even if one thinks they do, just a tiny gap in reasoning or understanding can often be exploited by a tricky question, making someone confused or writing things that doesn't make physical sense (though such problems can sometimes be the best ones to teach certain things!). I always liked, when some doctor or professor suddenly overhauled the fundaments of our understanding of a given topic or made some brilliant, tricky problem, just to vigorously explain it to us while we gasp at the clever reasoning!
This is amazing thank you so much, I'm in Year 10 (9th grade) and I have some small test on electrical circuits. I understand all the concepts but not to full depth like you have showed now. Brilliant
I thought this is how everyone saw these equations. Its crazy some people got through any physics or engineering degree without some fundamental understanding of these equations. Hats off to you! Must have required a lot more studying.
Have you never heard of a constant current source? Then, you need V=IR, since the current is constant, not the voltage. Also, have you never heard of a variable resistance? Sorry, dude, but you really don't consider ALL of the options. If you are a "rocket scientist" (isn't everyone at NASA?), then you understand about variable mass, constant acceleration, etc. right? Both of those equations need to to rearranged to suit the circumstances. Claiming that one form is more appropriate than another all depends upon the circumstances. Take care always.
That makes sense, however in highschool all we study is about a constant voltage source and a bunch of constant resistances. That's why we need I = V/R . The prior thing in schools should be to teach the way things work. Not how you plug in some numbers into an equation.
Doesn't a constant current source manipulate the voltage supplied, to meet the resistance and thus control the current? If that is the case, does it not deny that the voltage is the cause of the current? Just having a reactive system wouldn't meant that the causality was different.
@@LionKimbro A constant current source simply supplies a constant current, regardless of the load resistance. As the load resistance changes, so does the load voltage such that the current remains constant.
How do constant current sources work though? I had it in my classes, but never actually understood what are these. Voltage source are easy - we use it everyday in forms of battery. But I couldn't think of current source. Maybe some phone chargers? They often have let's say 1A charge current. But isn't it in reality the byproduct of voltage (from the socket)?
@@PinkeySuavo Well, without being an electrical engineer, as I see from your text, you just demolished @ulyssesfewl1059 approach :) A constant current source maintains current level by raising/decreasing voltage. Same for voltage sources with current. No matter how exactly they do it.
You're actually right. Understanding the basic fundamentals of the subject you are studying is really important if you're going to use it after you graduate in your job. I love physics, and I always try to understand the concepts, not just memorizing a bunch of formulas, and this understanding helps me to solve physics problems even if I have forgotten the formulas, like remembering concepts and then making the needed equation. V=IR was a good example, which a flow of electrons through a resistant material, doesn't cause electric potential difference because the movement of electrons itself has a cause which is potential difference, but it would be great if you also mentioned the capacitance formula: C = q/V so, according to the equation a student at the first glance might say, if we increase the voltage of a capacitor, the capacitance will decrease. But that's not correct! The capacitance of a capacitor is always the same and doesn't matter on voltage or the amount of charge. Instead, I would think that q = CV is better than the initial formula(C is constant value for a capacitor) to understand a capacitor. However, both formulas are correct if we don't forget the cause and effect.
These are Equations that are more general that functions. I think functions are useful when we want to see equation behaviour with respect to changing values of one term (variable). Since this is a monomial equation, F=m×a, F/(m×a)=1, a=F/m ... are all the same and each term could be assumed as function of 2 other terms. However there are some more generalized forms of this equation in dynamics. For example in Mass-spring-damper model, equation is formulized for F. Considering time varying parameters we have: F(t)=m.a(t)+k.x(t)+c.v(t) In other words, each one of above terms are in form of Force (inertial force, spring force & damping force). Also since it is a diffrential equation (a=v'=x'', and v=x') we can not simply re-arrange and solve them as a(t)=F(t)/m-(k.x(t)+c.v(t))/m, since x, v and a are dependent to each other. I'm not electrician but remember similar equation in RLC cirquits: V(t)=Vr(t)+Vc(t)+Vl(t) Where Vr(t)=R.i(t) is the simple form equation.
When discovered that coulomb's law is due to gauss's law but not vice versa , I experienced the same thing and understood how weirdly this world has arranged physics into our books 😅 I bet 19 of my classmates would even shock after knowing this if I tell them .
You can say they're all constant in Ohms law, because it really only hold true in a static case, an instateneous moment in time. Sure you can get accurate enough results for a circuit in "steady state" but if you've ever measured a circuit you will see that even the resistance value of a single resistor will fluctuate, even more so if you breath on it.
And actually if you really see it deep down and understand it... Force is really just potential energy gradient (for conservative forces like gravity) and V is potential difference something along the lines of potential energy difference (for unit positive charge)...and so they both depict that energy difference cause motion in certain particles. And both actually accelerate the particle ... but in case of current we define the average drift velocity and so the acceleration of electron fades away from notice because of the averaging part. So both eqns depict force fields that cause change in state of motion in particles like a normal object of mass m or a negatively charged electron.
In the equation V=IR or solving for I we have I=V/R it is important to understand that I is a RATE; i.e., the rate of change transfer. The more appropriate statement should be that current is the rate of transfer of electrical energy. V is potential energy; i.e., Energy can be potential and kinetic. V (potential) is waiting for a path to be provided so that charges can move. Once a path is provided, the charges become a current; i.e., I = dq/dt. This insight allows for a rational interpretation of 'a' in F=ma as a rate as well. It is very important to recognize that the acceleration of a mass is analogous to a current flowing through a resistance. Conclusion: Study Calculus before Physics.
Clearly never done any electrical (and mechanical) engineering. 10:22 "resistance is already there, so the current is the product". Every non-linear device adjusts its resistance based on the current supply. Negative differential resistance devices struggle at hunting down the correct resistance value so bad, they become oscillators. But even theoretical electronics disagree with you. Many circuits use constant current sources where current is the input parameter. Their models are very practical for photoelectric effect simulations. Same but worse with mechanical engineering. Nothing causes anything in mechanical systems. The 3rd law of motion and impulse preservation laws state that all effects are mutual, not causal. This video pushes for using a worse form of the formula for an invalid reason. There is a reason these formulas are in the equational form and their transformation to a functional form is heavily context dependent.
@@anghme28ang11 Nope. You can a have a current to produce a voltage. Electrical current is by definition the change of charge over time I=dQ/dt. You can move charge with a magnet and make them change over time hence creating a current.
How do current sources work though? I can imagine one as guy above wrote - using some magnets. But I can't imagine it in terms of battery or something.
@@PinkeySuavo most current sources are a voltage source modified to target a specific current. inductors are a true current source for a moment of time. inductive spikes are exactly when an inductor tries to maintain its momentary target current no matter the voltage. these spikes will physically damage any insulation in their way just to ensure the flow of some current.
Bravo! Very clear and demonstrative in real world dynamics. My chemistry teachers were big on application after the book learning. Every test had real-world application questions on them. I was already in my mid 30's and had the same mindset. If I felt that the class of the "kids" (just out of High School) sat there stumped, I would ask a question I already knew the answer to because it was on everyone else's mind and I didn't care if I looked stupid. The class often became a conversation between the professor and me while the others took notes. lol. Best student/worst student. I found it difficult to shut up and let other students engage.
Hi Ali, I’m a first-year electrical engineering student, and I’ve been searching for books that explain the underlying concepts in circuit analysis. In my course, we’re taught methods to solve for current and voltage in complex circuits, but they often feel like 'black magic'-given without explanation of where they come from or why we can make certain assumptions. I’m also looking to understand how electricity works on a deeper, more physical level. For example, how do electrons actually behave when a circuit is powered on? How does the signal propagate in wires to create a specific current with a given resistance? And what is really happening across a resistor-are charges accumulating, or is something else happening? Proof of KCL and KVL, why resistors in parallel have the same voltage etc... If you could make a video on this topic, recommending books that provide deeper insights into these concepts, it would be greatly appreciated.
Proof of KVl? In university physics 2 you will realize that KVl is just Faraday’s law from Maxwell’s equations in a special case where the given system is conserved. Walter Lewin (MIT prof) further explains this in his channel. If you want to learn circuits study any university physics textbook (Freedman or Halliday are greats ones!). After that you could study electrodynamics (Griffiths)
KCL is ultimately based on conservation of charge. Charge entering a point = charge leaving a point, since charge cannot accumulate at a point (unless it is a capacitor, but just a point is not a capacitor). Even capacitors have their own conservation of charge law. KVL is a special case of Faraday's law of induction. Essentially, when there are no inductive sources of voltage due to changing magnetic fields, electric fields are conservative. This means the closed loop work done on any charge, is zero. "What is really happening across a resistor"? Charge is not accumulating anywhere, rather the charge flow is competing with the thermal motion of the charges to proceed forward. The thermal motion is chaotic and adds up to zero among all the electrons, and is significantly greater than the electron drift. The electrical motion adds a slight bias in the direction of current flow that causes a net flow of charges. To overcome the chaotic thermal motion, it takes an electric field thru the component to bias the flow of charges to where they need to go. This means work is done on the charges to get them to move beyond what just their thermal motion is. This work done on the charges is what causes the voltage drop across the resistor. "How do electrons actually behave when a circuit is powered on"? The electrons already fill the circuit. The electric field propagates at nearly the speed of light through it, and disturbs a large quantity of electrons at once. This causes them to no longer just move randomly for their thermal motion, but also to move in the direction the electric field forces them to move. One of the most remarkable parts of this question, is that the electric field propagates, even where there isn't a wire. Derek from Veritasium has a thought experiment about this, where there's a battery and switch, that's 1 meter across from a bulb, and a circuit that extends 1 light second in both directions. His question was how long does it take the bulb to light? 1 second? 2 seconds? 3 nanoseconds? Or 1/2 second? The answer surprisingly is 3 nanoseconds. The electric field actually propagates across the 1 meter gap first, and causes current to flow through the bulb, before it can even complete a round trip through the circuit. It doesn't sustain significant amounts of current, but current flows nevertheless. You need to complete the circuit to maximize the efficiency of power transmission, but you can still transmit small amounts of power, before a round trip is complete. Alpha Phoenix has experimental evidence that supports this theory. He constructed this thought experiment with a kilometer of wire, and a load that was 1 meter across from the source and switch. He tested it with a state-of-the-art oscilloscope, and showed that you get power transmission faster than the round trip time for the circuit. You don't get full power transmission until the round trip is completed, but you still get some power transmission in the time it takes the field waves to propagate just 1 meter.
Sorry Ali, I have to quibble about V=IR. There are lots of places in electrical engineering where we use constant current sources and current mirrors. So, unlike the familiar battery, which provides a (roughly) constant voltage, these circuits provide a constant current, and the voltage generated across them depends on the resistance you place in the circuit, so V is indeed caused by I and R, or V=IR. To drive an LED, you don't control the voltage on it, but the current through it - if you ask "what voltage do I need to drive this LED?" and then pick a voltage supply equal to its forward voltage drop, part tolances mean you could drive too much current into it, or even kill it as temperature goes up - as diodes conduct more as temp increases, and "I" is an exponential function of V and T (temperature). To design a proper LED driver, you ask "how much current do I need?" and pick an appropriate resistor for your voltage supply, which can be anything above the diode(s) forward voltage drop. (But this assumes you're using a battery-like supply, and not a constant current driver). So although the current does develop a voltage drop across the diode, thinking of that as being "caused" by the battery/voltage applied by the power source doesn't help you pick the right resistor for the circuit. Arguably though, a more interesting equation is V = L * di/dt. This equation DOES follow your causality notion as it is, but not in the way most people expect. If you've unplugged a vacuum cleaner while the motor was still running and seen a bright spark at the outlet, you've seen this equation in action. The "V" in this case is NOT the voltage at the outlet (120V in the US, 240 in other parts of the world). Unplugging the outlet quickly decreases the current in the motor - and since the motor is a bunch of inductive coils, they each have an inductance "L." That sudden drop in current (di/dt) means the energy stored in that inductor will suddenly create a high (negative, compared to the way the inductor was just powered) voltage large enough to break the resistance of the air, and create a high-voltage spark between the outlet and the plug. That spark can easily be over 1000 volts, as is the voltage across the inductor as well.
@@alithedazzling A current mirror acts like a current source, and doesn't use "monitoring" of a voltage - i.e. no feedback measuring output current and adjusting it.
I always teach my students to think of ohms law in 3 ways depending on which term it is expressed in: V=IR - Ohms law, V is directly proportional to I if Rbis constant at a constant temp R = V/I , defining equation for Resistance and what is meant by an Ohm. I = V/R , the only format that (as you say) expresses the causes and effects on each side of the equation. We don't change current to change V or R, but if we change I it is only because we are also changing V and/or R. I think all three ways are needed to help students fully grasp the idea of thinking deeply about core concepts. Side note: your casual use of language had me concerned. Current is not a flow of charge, it is the rate of flow of charge for example. You also mentioned speeding up the Voltage, that is a big cause for an effect of misconceptions.
So what is a flow of charge then if not current, what would call it?? When you want to express the rate you use units of amperes (coulumb/sec) to quantify the rate, amps is the rate of the current. Not to nitpick you, but please explain how what I've said here is incorrect if you disagree.
@onradioactivewaves electricity is a flow of charge in which there is a current. But the flow isn't the current, but a sign there is a current, if that makes sense. In truth the difference is subtle and to most it isn't a problem. But if you are studying the topic an exam will require the correct use of the term.
@@dakeyrasuk I have studied it and I've also worked in an electrical field (no pun intended) where many terms were commonly used interchangeably and incorrectly. The word electricity is pretty generic and can mean many different things, but in general can be assumed to mean pertains to electrical charge / energy. Current can take one many different forms/ meanings as well. It could be drift current, AC or DC current, dispersion or diffusion current in a semiconductor. These all had very precise mathematical definitions when it came to exam time. I kind of get where you're coming from, but the same general word can have very different meanings depending on the context. One person saying electricity could imply charge flowing in wires, in another context it could be referring to a static charge causing a persons hair to stand on end no current involved. Unless in a particular context or more technically described, general terms can be very ambiguous. I might use electricity instead of current if talking to 4 year old, whereas saying current in regards to a semiconductor without any other context could be nonsensical. I've had these discussions with professors, students , engineers, many of whom do not speak English as their first language ( technically not my first language either) At first this was difficult for me, but ultimately forced me learn how to communicate better technically and precisely (I've also had to read and write plenty of technical documentation). So while I can agree with what you've said, there's always going to be different interpretations.
I agree, but there can also be the other approach of writing the equations in the order where things were defined. For V=IR, what actually happened is that scientists saw that you take different materials and put them under voltage, and you get different currents, which led them to define resistance as R=V/I. So your equation can either say "voltage causes current according to resistance (I=V/R) or "resistance is defined as the ratio of voltage to current in a material". For kinematics, mass and acceleration are easily measured, and the force was defined later, so F=ma is the way to write it under this style.
Intuitively it makes sense to me as well. in my current understanding, emf and resistance are properties of the battery/components that can be tested in isolation and won't change based on the circuit it's put in, but current isn't exactly a physical property that can be tested in isolation and can only be derived from the situation of the circuit.
I really expected more from this video like diving deep into what current, voltage and resistance really is and how they truly relate. This more fitted for high school students. I like your thinking pattern but it's to general for my taste. I don't mean to sound arrogant, it's a good video and you are a good teacher, I was just hoping for more.
The point of this video was to teach the basic concept, It was not meant to go in detail. If you had paid attention from the beginning you would've known...
It is not a force as in mechanics, but it is an impetus. But when a given impetus exists, does the flow of electrons ever fail to equal the potential flow? Well, yes, as in inductance or capacitance. So it may be like the flow of water down an inclined plane, with little traps occasionally for the water that slows it down more than just the angle of the incline.
OMG! It's the first time that even physics makes logic or else in our school we are just taught to plug in some random numerical and the better you are at it, the greater marks you will achieve. Thank you so much for making a great video, eagerly waiting for more of this kind.
Interesting perspective. Our physics teacher at school liked to write the 3 symbols of these kinds of relationships in a triangle e.g.: V I R So you remember that and can generate any of the 3 equations you need, there's none of the "this is *the* variable we want to calculate" suggestion that you talked about. Btw the causal relationship isn't so clear in electronics e.g. if you connect a photodiode (or even just an ordinary LED) to a resistor and shine light on it, it will generate a current, and you can measure that current by the voltage across the resistor, so V = IR.
I have electric circuits in my course and the way you have explained on WHY and HOW these things work really made my concepts clear And I think people will actually be able to relate with these concepts if they visualize it themselves rather than memorizing the theory And honestly visualizing these things is what makes Physics more interesting and fun to learn I'm so glad to have watched this video Thanks :)
The way I understand V=IR is actually to say if you have a load resistance of 10 ohm and your circuit must be able to draw 2 Amps, you will need at least a Potential difference (Volts) of 20 Volts to achieve your goal, but definitional wise to explain the equation, yours makes much more sense!
This is related to directly proportional... Like if a man fall from the top of the mountain he will get hurt. But if another man got hurt it doesn't mean that man felt from the top of the mountain. So here If someone fall from the mountain he/she will definitely get hurt. If someone is already wounded it doesn't mean that person has fallen from the mountain.
For the past four years when I was studying engineering, I was always thinking about the same thing that you said and that video we need to look at things in terms of cause and effect and reason I'm so happy that finally someone pointed that out
I have a bad effect of hypersomnia while studying. But your teaching methos kept me focused & beat that thing. Thanks sir. Eager to learn more from you.
Sir hats off to you! I am familiar with both of these equations but never thought of such understanding. Now I feel superior in my classroom after knowing this and i have also made sure that my friends are amazed too. Going to be a high school student soon and I will be pleased to dedicate myself in learning more concepts from you. Love from India 🇮🇳
I think your video highlighted some really good points about how current plays an important role in circuits. But I believe what's even more crucial is the interworking of energy-specifically, the potential difference. The voltage in a battery comes from the potential difference created by the electrochemical reactions inside. For instance, a standard alkaline battery gives 1.5 volts because of the specific chemicals involved, and when you combine multiple cells, their voltages add up. That’s why you often see batteries in series to achieve higher voltages (like 3V or 9V). When it comes to the structure of a battery, multiple cells are combined to increase the total voltage, and this organization creates that "hunger" for electrons to move from one side of the battery to the other. The size of these cells is directly linked to battery life, or capacity, because larger cells hold more chemical material, which in turn allows for more energy storage. Regarding voltage drop, the voltage stays relatively constant during most of the battery's life. It remains steady until the energy is almost gone, at which point the voltage drops rapidly. This happens because the battery can no longer sustain the chemical reactions at the same rate as before, leading to that sharp decrease in power output. As for **resistors**, they are made of materials that prevent electrons from moving through them very quickly, kind of like plugging up the flow of the battery’s discharge. The pressure (voltage) from the battery remains the same, but because of the resistor, the energy cannot discharge as quickly. In other words, the resistor limits the current, so while the battery’s energy is still there, it’s released more slowly. The energy loss that happens in a resistor is converted into heat, which is why resistors can get warm during use. One thing worth adding is the role of **resistance** in this process. As the battery discharges, internal resistance tends to increase, which can further lower the voltage output as the battery ages. In circuits, external resistance also determines how much current flows for a given voltage Ohm’s law: V = IR meaning a higher resistance will limit current flow. So, battery life can be affected not just by the capacity but also by the resistance within the circuit it's powering. In short, voltage stays relatively steady, the capacity depends on the cell size and chemical composition, and resistance plays a critical role in how much current can flow and how long the battery will last before reaching that rapid drop in performance.
Sometimes, in electrical engineering, we have a constant current and we have a target Voltage, so we need to solve for R. Old school Ammeters gauge a current through a known resistance and that is how we measure voltage. Plus, once you start adding inductance and capacitance into the equation, physical analogues start to have less utility. I'm not saying this is wrong or that no one would benefit from this line of thinking, but I think most EEs would prefer to think of V=IR as simply a relationship between electrical properties... Just my opinion - I could be wrong.
Yep, i totally agree with this, and i've of it myself just a few weeks ago. It's far easier (and it's how i've been understanding anything in physics till now) to see a formula as a rule of causality, with the cause and the effect. It's not necessarely the truest way but it's definitely the one we can understand.
An equation can be seen in many different ways. The cause and effect can be other way round too if we start talking in that way. But you're correct in mentioning that causality brings life to Physics. 😊
WOW. Glad I stumbled onto this. I wondered where you were going with this at first and you take too long to get the the root of the issue - cause and effect. From comments saying they never thought of cause and effect, tI can see they have indeed, learned very poorly. . You are on to an important point that I have seen for quite some time. The cause and effect is VERY IMPORTANT and if that isn't taught any more, that is very sad, because it isn't teaching. . The equations NEVER show cause and effect. They ONLY show what happens - not why. Which are dependent variables and which are independent variables. . In the beginning. When scientists study things and provide equations: . The physical behaviors are understood FIRST. THEN. They learn how to quantify the values. THEN Then find the equation that mimics the real, physical world. THEN Then, We can use the equations, but we must understand the underlying physics to use them correctly. . The equations are a model of the physical world. Equations do not define the behavior, nor control them. They are a tool that imitates the real world's values. . Advice. . . .. For one thing, F=MA starts when the guy PUSHES On the ball. His force accelerates it horizontally. The slope and gravity complicate it more than necessary. . Then, Mass resists Acceleration. The fundamental, physical property we call Inertia can be said to describe that resistance. Let's teach that! . I have felt for a long time that we need to re-describe Newton's Laws of Motion because too few truly understand what they really tell us. I think it is simply a desire to retain Newton's words, but the real meanings are also lost. . Newton's First Law tells us that Force is the CAUSE of ACCELERATION. . The First and third Laws tell us that Inertia resists Acceleration and that 'resistance' is why there is what he calls the "reaction". Therefore, we can say that Inertia is the Cause of the Third Law 'reaction'. . I've seen beginners confuse cause and effect from the wrong interpretation of only the equation. . Seeing others say they didn't consider cause and effect is very sad. . Perhaps this is why I have seen some so-called engineers that don't really understand their subject. . From an experience engineer.
I thankful my teacher taught me that way. The original formula is I = V/R which actually is Ohm's law. The V=I*R and R=V/I are byproducts of Ohm's law. Also as you correctly said, we are not changing the resistance nor the battery meaning that they are stable, so the I is dependent on those and to be on a closed circuit. Change the battery with lower volt, the amps will charge, the resistance will not. Change the resistance, the amps will change, the volts won't. So I'm really thankful my teacher taught me how to think. And I really love your video. It makes us think.
Cheers Ali ! I haven't ever looked to physics equations this way , now it makes much more sense, If only teachers used this way of intuition in Iraqi schools .
my physics teacher actually taught us about the cause and effect in Physics which really grows on me and thinks more about what the idea behind each equation is. Beside I like equation in their vector differential form lol (or integral) because it just give you so much more understanding (and able to solve non uniform problem)
I love the message of this video! When I was learning kinematics in high school, our teacher simply gave us a formula and told us to plug in known values to solve for the unknown. That’s it. There was no intuition or explanation of how and why the formula worked to calculate projectile position, and this really bothered me. I decided to start from scratch and derive the formula myself using my intuition about velocity, acceleration, etc. I eventually came up with the same equation the teacher originally gave us, but my version was factorized and allowed me to see exactly how the individual terms worked together to show projectile position, and why the final equation looked the way it did.
Do you have any possible resources you could suggest using? I’m having the same exact problem right now and am also trying to balance teaching it to myself from scratch
@@Milkenj0yer So far, the most helpful resource for me has been Khan Academy. It has a vast number of video/reading lessons covering many courses ranging from kindergarten to the college level. All the lessons have easy to understand explanations and illustrations, and they also provide quizzes and practice problems that help you progress your knowledge through the course (and everything is completely free). I've also heard of an app called Brilliant that teaches math and science through interactive lessons, which helps with intuitive understanding of concepts. However, I can't speak from experience since I haven't tried the app yet, but it seems to have a very positive reputation among users.
@@Milkenj0yer So far, the most helpful resource for me has been Khan Academy. It has a vast number of video/written lessons covering many courses ranging from kindergarten to the college level. They always explain topics thoroughly with illustrations, and provide quizzes that test your knowledge to help you progress through the course as if you were learning it officially with a real teacher (and it's all for free). I've also heard of an app called Brilliant that teaches math and science using interactive simulations/lessons, which is really helpful for building intuition and deep understanding of concepts. I can't speak from experience since I haven't tried the app, but it seems to have a very positive reputation among users.
@@Milkenj0yer So far, the most helpful resource for me has been Khan Academy. It has a vast number of video/written lessons covering many courses ranging from kindergarten to the college level. They always explain topics thoroughly with illustrations, and provide quizzes that test your knowledge to help you progress through the course as if you were learning it officially with a real teacher (and it's all for free). I've also heard of an app called Brilliant that teaches math and science using interactive simulations/lessons, which is really helpful for building intuition and deep understanding of concepts. I can't speak from experience since I haven't tried the app, but it seems to have a very positive reputation among users.
@@Milkenj0yer So far, the most helpful resource for me has been Khan Academy. It has a vast number of video/written lessons covering many courses ranging from kindergarten to the college level. They always explain topics thoroughly with illustrations, and provide quizzes that test your knowledge to help you progress through the course as if you were learning it officially with a real teacher (and it's all for free). I've also heard of an app called Brilliant that teaches math and science using interactive simulations/lessons, which is really helpful for building intuition and deep understanding of concepts. I can't speak from experience since I haven't tried the app, but it seems to have a very positive reputation among users.
Such a good video and thank god someone has posted it. I have been teaching Physics for over a decade but students just don't get it when I say, "we are doing physics, not maths." However, I agree with a=f/m but Ohm's Law is best explained as R=V/I and current as I=Q/t
In Highschool I passed physics very well, but after graduating university. I started learning it on my own, that is where I realized that I didn't understand it before.
How did you start learning it on your own?
Fr. I am in highschool and i understand the real undercover meaning and what led the creator to create it. And by those mathematical thought processes I can even study it on my own !
You mostly read out of curiosity. It always happens @@udveetpatil8002
@@Forneutraluse4 creator of what?
@@nutronstar45math and physics
Learning to see relationships between things is true knowledge.
yes!!!
this is called systems thinking -- its extremely valuable!
Yeah, encourage the conspiracy theorists.
@@alithedazzling i like to connect the dots
@@glandeokrayo9956 It deppends on what assumptions you take and where you take them from
Thank you! This is exactly how and why I teach I = V/R and a = F/m as well.
And you think there is a dfr 😅
Po-tey-toh, po-tah-to...
I like to conceptualise voltage as E = -grad V, it is the gradient vector field of the electric field. This idea is often more intuitive. And I like to think about current as dQ/dt = V/R. The differential or integral forms are a beautiful mathematical description that is also accurate describing gradient fields and rates of change.
Naa F = ma because force is change of momentum with respect to time and when we have mass as a constant and dv/dt is acceleration.
@@bbd1603 Spot on, thank you!
Exactly, m=E/c2 was Einstein's breakthrough of the understanding of mass.
E=mc^2 isn't the full equation though. It's E^2 = (mc^2)^2 + (pc)^2. m=E/c^2 is literally physically impossible. It's just an approximation.
@louisrobitaille5810 those are 2 different things tho. The first denotes mass-energy equivalence, the second energy-momentum relation.
1. It states that the energy (E) of an object at rest is equal to its mass (m) multiplied by the speed of light squared (c²) This implies that mass can be converted to energy and vice versa. It specifically refers to rest energy.
2. This equation is the more general form that applies to objects that may be in motion.
@@schwobelabibalbol no that's not it
E=mc² is when object is at rest which is likely not the case making p=0. Full formula is E²=(mc²)²+(pc)²
Yes same thing apply about converting mass to energy on E²=(mc²)²+(pc)² formula
@@louisrobitaille5810what do you mean physically impossible it’s always the case
@@baldurstudios5637 he means m=E/c^2 is physically impossible because it presumes that the object in question has zero momentum which is kinda impossible to know or have in reality--you can only have zero momentum relative to something else, which is different
Some people have innate understanding of equations and notation, and have a “the way it is is just the way it is” type of mentality. They’re crazy smart people, but not great at teaching.
I totally agree with your explanation! This is how I approach engineering fundamentals, from physical phenomenon to written notation.
Expression, I guess
I don't think an innate understanding of those things exist, because they are entirely arbitrary notations and symbols.
@@GodVanisherNot really. In the same way 1+1=2 are just numbers and has a very intuitive understanding(one thing plus another is two things). There are intuitive ways to understand fields, derivatives, fluids, electricity...
@@next_door_rigil3270 Intuition is useless at some point. Everyday experiences do not align with how the world actually works. It’s just as wrong as common sense. Also I was rather focusing on the syntax and semantics of the language, which are arbitrarily chosen by humanity. Language can only be understood with references.
@@GodVanisher If a person can imagine physics properties or analogues to them in their daily lives, you are able understand them really well. And we can find analogues for most concepts we know. By understanding them, I mean being able to qualititavely predict future states of a system in your mind. The mathematics is an extension of that model. It is how we even got Eistein's relativity. Intuition came before mathematics. The quantum realm is more complicated but it is also possible.
Why is your explanation so clear and concise? I cant stop listening to you i enjoy learning from you, love you so much❤
glad you found it useful!
It's far from concise but it does provide a different point of view.
understanding is propably just dependent on point of view
Have been really enjoying this recent chalkboard series
@@tyler77776 big same. Love mini-lectures.
I am an electrician and I make videos. I often find the problem with comments from electrical engineers is they only understand a mathematical analogy without really understanding what's going on and I think that's the point of your video.. love it I try teach electrical theory with minimal math and maximum working live voltage demos
you got the point, exactly!!! thank you for this comment :)
Ayyye, I know this guy!
The math is very very important to understand electricity. No offense but I find it almost impossible to believe even an undergrad EE would not understand ohms law far far past the point of this video. Understanding the math is what leads to the true understanding of how electricity works. Like you just cant have a good understanding of impedance for example without understanding complex phase.
@@YoungJackRack oh great, the academic has arrived.
Also, what the fuck does "even an undergrad" mean?
There are more university students that cant wipe their own ass than high school drop outs, so what exactly is your point?
@@YoungJackRack I have 200k followers and get tons of comments from EE that say the USA 240v system has 2 phases 180° out of phase. I hear them say electricity flows to ground. I hear them say a neutral carries only the imbalance because current is canceled. All of those ideas are just for math but to not reflect the actual function or installation. I have literally seen EEs comment higher volts means lower amps.. I work with EEs at a shipyard some are good some but some know very little about how to bring their math to life in the real world.
Wow this was a really new way to see these equations together! Physics is so much fun if taught properly but it's unfair we don't get to learn in a fun way:(
idk I'm having fun
idk I'm having fun
It is easier to memorize F=ma. To memorize a=F/m you have to remember which one is on top. You can always change F=ma to the firm that is useful for each situation.
V=IR is useful you know the resistance and measure the amperage and need to determine what voltage is driving that amperage. So the form of the equations to use depends on what you not to find and what you know already.
You should do a video on why 0 Resistance is impossible.*
*Edit: My knowledge of Superconductors was outdated, so some of my comments in this thread are (partially) incorrect.
Yes, Superconductors with 0 resistance exist. So, instead, they have Current Density. This, as @Miyomotomusashi69 stated, is something closer to how batteries store electrons.
*However*
This does not disprove that in Ohm's Law I=V/R, R =\= 0. When you do not have a dedicated Resistor, you use the resistance of the wire in the circuit. More accurately, you just end up creating heat within the circuit. This is in fact how a traditional light bulb works. Superconductors follow the London Equations, which only work in quantum mechanics.
Wait so superconductors are not really superconductors?!
@@mistadude *near* 0 resistance on a superconductor.
Remember, dividing by 0 is impossible. Mathematically and in real life.
If you were to say "How many apples did you sell in x day(s)?" [Sales=Apples÷Day(s)]
But, I spent 0 days selling apples... well I didn't have any sales of any apples then. There is no equation to speak of.
@@treeross this is true for conventional circuits, but superconductivity breaks this law due to the concept of cooper pairs, where the electrons are cooled enough to where they form positively charged "phonons", which are matched in a way that makes them behave as a single entity. Once enough of these phonons are formed, they condense into a ground state that allows them to move without scattering vibrations or impurities, thus creating zero resistance. Look up BCS theory for a deeper explanation.
@@Miyamotomusashi69 wouldn't the current still not exist in that case? Because current is a measure of V/R, without one value you can't use that measurement, right?
@@treeross the phonons do not behave like traditional electrons, when they are paired they are put into a quantum state and move through magnetic expulsion from the inside of the superconductor, which is how they exhibit current without voltage. Although a voltage is initially present which supplies the superconductor with electrons, once these thermal reactions occur the electrons are essentially "stored" within the superconductor, where they can flow without dissipation of energy. This is quantum mechanics, which goes beyond the realm of normal electrical circuits.
As a highschool student, my eyes really lit up when you got around to explaining the circuit example in the near end of the video. This feeling resonated with me because when I first learned this initially in 9th grade it confused the heck out of me whenever this equation V=IR popped.
What you should have retained from high school is that V=IR is the equation for OHMIC conductors. It is not a useful equation for conduction in gases or liquids. It doesn't work for metals at high currents, either, because of heating effects. THAT would have been the important lesson to remember.
@@lepidoptera9337 - Did you miss where he started his post saying he's a high school student - and that he learned this in 9th frade? So that wasn't even likely a physics class, but a physical science class. Even in high school physics, they don't normally get into that. They have a lot of material to cover. It's a survey of many topics at an introductory level - not an in-depth electrical circuits class.
@@Curly_Maple I was talking about the "NASA engineer" guy who made this stupid video.
Truly underrated video! Nowadays, schools are blindly teaching us these equations and telling students that "it's just like that" and expect us to memorise it. As someone who formerly struggled with physics, understanding the core reason why the equation is in a certain way with practical analogies (like what you did in the video), would make physics a lot more intuitive for many people!
Please keep up this amazing content! Would love to see more physics videos from you. Would also love to see you touch on harder content (e.g. quantum mechanics, relativity) as I find that you break down these difficult concepts into digestable information!! :)
Interesting that the way you "rewrote" the equations was actually the way that we were taught in high school physics. Our teacher was a 1930s US Navy Academy graduate, so that's where he learned his physics. Your instruction brought back some memories of Mr Conger, thanks!
I’m currently taking PHYS I hear at Cornell…which, as you probably imagine, is tough as nails. Thanks for putting the world of physics into such an understandable manner!
Many people are misunderstanding the main message of the video. It's not about simply writing equations more precisely. The core idea is to emphasize the fundamental understanding behind those equations. Too often, students focus on memorizing formulas and solving problems mechanically, but this approach misses the essence of physics.
Physics is not just about calculations-it's about understanding the nature of the world and the interconnectedness of its phenomena. The true purpose of studying physics lies in grasping the origins and meaning of equations, not just applying them blindly. Before committing formulas to memory, it's crucial to comprehend where they come from and why they work.
I fully agree with the video’s perspective. Thank you for shedding light on this important aspect of learning practical physics!
This makes me happy because most teachers don't teach the true meaning of the formula but the values they put out, and students end up losing the true meaning of the formula of what it is really about🥰This is good to hear from someone else but myself☺
Well actually Mr. Postdoctoral Fellow, it is more properly written as I = V / ( R + jX ). Only noobs leave off the imaginary part of the complex impedance. Joking aside, it doesn't matter how the equation is arranged, it all maths out the same. I do recall years ago ignorantly thinking that if you just increase the resistance of the circuit enough then you can generate any arbitrarily high voltage, not recognizing what is driving what in the relationship. The problem with saying it has to be written as I=V/R assumes that voltage always drives current, this isn't always true. Currents can be induced via inductive action, changing magnetic fields, or by physically moving charged objects around; in these cases, the voltage is generated by the current and/or the reactive impedance. Electrical Engineering is a misnomer, it isn't the electricity that is being engineered (that part is governed by physics), it is the impedance that is engineered in order to control the VI relationship.
Impedance is SI defined as Z = E/R
Even more damaging to main argument of this video: ALL real voltage sources exhibit an equivalent series resistance. Because of this, by using the well known theorems of Thevenin and Norton, any real source can be represented either as a voltage source (with a series resistance) or a current source (with a parallel resistance); they are equivalent.
The reason why in shool are used Simple Models like a gravity, 2nd Newton Law, Ohm Law or Energy of principles is only to capture initial understanding of basics. If You starts analyze the e.g. the diffrerential equations before the static understanding , this is not efficient way to understand the problems. The acceleration also can be driven (Simple example the stepper motor which driver gear and You want to observe the response of the hit for example or pressure)so this is correleted to the context but remember. Math is only approximation and You dont have 100 percentage model describes real. No, You can be close to real. A = f/m is crashed when You add relativity for example so 😊this is not proof,proof is the experiment and observation, however still with some deviation ;p
@@georgejo7905 Impedance has the unit of ohm which is SI defined as (kg*m^2)/(s*C^2). Since it has real and imaginary parts, makes you wonder which base units become imaginary? Capacitance and inductance have reciprocal units with exception of s^2 so there could be an argument that time is imaginary. This fits well considering that magnetic effects could very well be the consequence of relativistic effects on electric charge. And we all know that relativity makes time weird.
@@Commenter-f8b if the impedance is only imaginary ( reactive) the solution is complex time.
Epitome of never stop asking why instead of taking things at face value . Amazing video and i wish you could make beginner friendly videos down to highschool level physics
Well said. Something I’ve always understood intuitively, but this is a good reminder that I think I’m going to try to keep in mind more when tutoring other students.
As a high-school physics student, this is a small detail that has bugged me for the longest time. Thank you for speaking about this ❤
Good video. Your approach to physics is very good, very reality-oriented.
Bullocks. 😂
As a qualified and experienced teacher math and physics I completely agree with you. However I teach 12 - 16 years old kids and when I'd try to explain this rather philosophical topic to them it would fly way beyond their yet incompletely developed brains. So I restrict myself to merely telling them that force can cause ao change in velocity (which I demonstrate by throwing my blackboard eraser through the classroom, so that they never forget).
A somewhat similar issue rises when teaching Galileo's equations for motion. I teach the common, simplified versions (s = v.t). The students who graduate and continue with physics at highschool (it's called differently in Suriname) get the formal notations as functions. Sure enough my own son reproached me when he found out.
My remedy is making clear that whatever I teach it is simplified. In the end this is true for every theory in physics (or in science in general). What teachers need to avoid is implying that we present the absolute truth. The theme that returns over and over again in my class is that reality is always more complicated than we think.
Hey ali , I 've been watching your videos for a while now and I really have to say that they inspired me to pursue electrical engineering,I was stuck at mechanical engineering and I kinda gave up but your videos really helped me remember why I liked electrical engineering in the first place and see other interesting aspects of it , I am starting this semester in electronics engineering school and I am majoring in communication engineering . Thanks to you I was able to take this choice and I can't thank you enough for this.
Thank you for this. Really glad you popped up on my feed. 🙏🏽
5:49 Kinda weird analogy. Gravitational and electric potential on punctual charges are both proportional to 1/r, but the former needs a much larger scale for it to start acting like the latter. Gravitational potential is so hard to change that we consistently assume our classical mechanics problems happen assuming it's constant. Electric potential can be modeled as non constant p easily. That's why it's recommended that You don't think about change in eP with the same arguments as the change in speed using gP.
Changes in acceleration in classical dynamics are more affected by air resistance than change in position
You cross out V=IR and F=ma like you have a more fundamental understanding, and then you just re-explain the equations. You are better at marketing than engineering...
I think you missed the point
@@dariosarubbi3129 His only point was that he is not qualified as a science teacher. He does not understand physics, not even at the high school level.
You completely missed the point, he really explained beautifully that how a function works, there is a cause and there is an effect.
@@scientificbhaiya9336 At least that's the kindergarten view of classical mechanics. It stops working as soon as I drop something because now there is an object accelerating downwards without any force whatsoever. OTOH, if I want to hold that object in place, then I have to supply a constant force upwards.
@@lepidoptera9337 Bro I think you misunderstood what a F is there. F is the Net force acting on the mass M, it is the overall force after adding resisting forces and supporting force, now here in the equation a=F/m the resistance is not friction but The Inertia itself I.e. the property of the mass to resist motion. And no object accelerates without a force, maybe you have a border aspect your saying, I’ll like to know more about it.
I've always thought this way and had the same thoughts. Equations need to convey causality. At least at the teaching stage.
Really fascinating. Please make more of these types of videos :)
Thanks Eugenia! Any specific topics you'd like to see?
Well, I am in high school studying physics, and I’m quite fascinated with how everything works to the very basics… things like how acceleration can make something not in equilibrium, or how we came up with certain suvat equations and the relationships between the actual values. I feel like if I can master the fundamental knowledge then it would be a lot more interesting and easier to add to that knowledge.
@@eugenia1286 very accurate thinking, you will go far in your career!
this is what changed my whole perspective about formulas and not just memorizing them without understanding the fundamental concept of the formula
You should do more videos about circuit and semiconductor physics
This!
This is actual gold. Thank you so much for clarifying this.
Surface friction is not going to stop a ball from rolling. In fact, it *causes* it to roll rather than slide. Energy is only dissipated if the friction force is nonzero, but too weak to prevent sliding.
Agree on the point made in the video though. When I teach physics, I always try to get the physics concept across, before introducing the mathematical formula.
I agree, wanted to see if anybody noticed. A better example would be with an object just sliding.
@@danielnastase5302 yeah, maybe a cube or something with flat surface
Surface friction is sufficient for rolling on any solid surface in reality and so is irrelevant to discuss in his example it is more so governed by the shape of moving object instead of the surface friction, a ball(anything mostly round) will roll on any surface.
Sliding of a ball can occur as you point out, simply due to a proportion of liquid/fluid state being present in the contact surface, none obvious in the example above.
The reason a partial liquid phase causes translation/sliding is like sliding of a ball on normal slippery ice. This is due to the ice being partially a liquid on its surface, hence the ball will partially react to the contact as sliding and partially react as rolling.
Surface friction would only affect an object that's shaped with a larger surface area touching the ground, because that would be an object that could actually slide with low friction, something like a cube instead of inherently needing to roll like a ball...
The shape determines if an object will roll on a given surface, unless you say there is no surface friction in a solid-solid contact, impossible. By stating the object is a ball means it must roll.
p.s. realistically there is always surface friction as I'm sure you know, this will indeed stop the ball from rolling over time by converting kinetic energy into heat, just because it isn't sliding doesn't mean there isn't heat created with every turn of the ball...
This stuff is so complicated it seems like every physics video I’ve ever watched no matter the creator always has a comment like this that’s like my goodness it’s just so much lol
I was going to say that!
Dude it's amazing.. please keep it up. Initially i thought i should skip this bcz i know all about therse 2 equations but still i watched and it blew my mind.
I thought of this a while ago and will add:
Even better, I = GV, where G is called _conductance._ Likewise while there is no usual symbol for it, we might say that a = ɯF, where ɯ is the reciprocal of mass - we might call it "susceptibility to force". So the interesting question is: from this perspective, why do ɯ satisfy 1/(ɯ_tot) = 1/(ɯ_1) + 1/(ɯ_2) when we combine objects together? Hmm...
Bingo! If someone would have explained things in the way you did in this video during my younger years, I would probably have gone on to study for a PhD instead of settling for a BSc. An excellent insight!
4:53 ma=f There is a more general formulation of Newton's second law, dp/dt=f, which states that the only cause of change in motion is interaction with other objects. The quantity of motion in this law is called momentum, p, and the force, f, is a measure of the interaction between objects.
i think the point here is to learn physics in manner of product and cause?really changed my perspective!
Wrong, you should write I -V/R = 0 because it's a relationship, not causation
nitpicky
this, but less confrontational
can somebody explain the difference between writing it as V=IR and I=V/R and I-V/R=0, to me they are completely the same
@@엉덩이먹는사람 As i understand then they are the same in that both sides of the equation are equal in all three of your examples, but he never claimed that this is untrue. His point was that it is useful to think of the right side of the equation as the cause and the left side as the effect and therefore write it as I = V / R, because V and R are the parts we control and I derives from them.
Good video, I think this was very insightful. The V=IR or I=V/R equation is just a way to show how those three variables are related. If you have 0 potential difference, you will have 0 current, and likewise if you have 0 current through some circuit element, you will have 0 voltage drop. If you have 0 resistance, you will have a very large amount of current. I feel like developing an intuitive understanding is important for this equation. What are your thoughts on using water pipes as an analogy for current, voltage and resistance?
Well, you are right 90%
F=ma is also correct way in a physical pov if... We were calculating the force that the ball exerts on the second floor due to being accelerated, so here the force is a function of acceleration, while in your example the acceleration is a function of the gravity force ((external force causing the acceleration)) but it is not the only force, the ball will also exert force which is proportional to a, so in that case F=ma is more ""correct""
Thankyuuu veryyy much as a student I love to learn with this kind of perspective instead of cramming physics
Teachers do not answer the "why".
very true -- which is the most important part!
Excellent and illuminating. Thank you. This and your elucidation of Maxwell’s equations helped me gain insight on both.
Your idea that equations should be written with the causal quantities on the RHS and effect-quantity as the subject on the LHS is an interesting and compelling idea. I guess, as a mathematician, I find equations involving just multiplication more "simplified" and "elegant" than the rearranged versions involving division - but from a teaching perspective (especially at, say, high-school level), your point might be stronger.
Regarding voltage and current, one of the things that confused me in school is learning about setups in which it's the supplied _power_ (rather than the resistance of the circuit to which the power is being supplied) that is externally predetermined, so that one has freedom to control the supplied current or supplied voltage within the constraint of their being _inversely_ proportional to each other, rather than directly proportional as in Ohm's Law.
Regarding F=ma, what's interesting is that, conceptually, it's forces that cause changes in velocity, but mathematically, the infinitesimal calculus places the change of velocity as simultaneous with (rather than temporally subsequent to) the force. This can lead to bizarre paradoxes like Norton's Dome, where one can define a dome shape [where there is a well-defined unique tangent plane to every point on the dome, and this tangent plane varies continuously with respect to the point on the dome] such that it's perfectly consistent with Newtonian mechanics for a point particle at the exact top point of the dome to stay at this top point for an arbitrary duration of time before spontaneously starting to slide down the dome. In effect, because of how infinitesimal calculus works, "F=ma" theoretically allows the 'a' to be the cause of the 'F', even though in practice it's the 'F' that is the cause of the 'a'.
If an object with mass m is accelerated because of the curvature of space, then it has a force caused by acceleration.
In this case, force is the output, and acceleration is the input. Or, force is the effect, and acceleration is the cause. This is a case which directly contradicts your point.
If I am wrong, please respond with a detailed explaination on why I am wrong. You are more educated than me.
4:28
I DISAGREE
as force is applied first and it causes the object to accelerate.
Correct me if I am wrong
what is a force tho?
@@youtube4eternity a push or pull
Thank you so much. I’ve always had a weird mental block with the concept of voltage because of this. I feel relieved.
I just got an example against "V=IR" : why is highest voltage ever produced about 25.5MV? Why can't we easily reach voltage in billions or trillions of volts, if all we have to do is increase the R? Then, we can proceed with what you said about causality and now it makes sense!
The Resistance doesnt depend on Current intensity or even the Voltage
Resistance of a material depend on
Specific Resistivity of it
It's length
It's area
If you increase resistance
You decrease the current flowing through
So the product of resistance and current is always equal to the volt of the source
If you want higher voltage
We need a stronger Source
So
I Depends on V and R
V doesnt depend on R or I
R depends on the material and its other properties
So increasing Resistance makes current decrease by an amount that always the Current.Resistance equals the Voltage of the source
That's why when you get introduced to electrical engineering of circuits
You always have that noted
R doesnt depend on either of them
Voltage is dependant on the source of it
And also
If you want to achieve higher voltage
By higher resistance
V=ir is correct
We have 3 factors
We want to increase v by increasing R right?
You can but then you have to control i at constant value.but as we know R affects current to be Lower When YOU HAVE THE SAME VOLTAGE..
@@ahmedalaa7216 Good breakdown, thank you! Like they say, proper understanding is the key to success.
I hope that education will be going more and more into properly explaining and visualizing certain concepts, as many people oftentimes don't properly understand what they are calculating, integrating, why we solve this or that equation, etc.
And even if one thinks they do, just a tiny gap in reasoning or understanding can often be exploited by a tricky question, making someone confused or writing things that doesn't make physical sense (though such problems can sometimes be the best ones to teach certain things!).
I always liked, when some doctor or professor suddenly overhauled the fundaments of our understanding of a given topic or made some brilliant, tricky problem, just to vigorously explain it to us while we gasp at the clever reasoning!
This is amazing thank you so much, I'm in Year 10 (9th grade) and I have some small test on electrical circuits. I understand all the concepts but not to full depth like you have showed now. Brilliant
Thanks, I'll keep this in mind when I give little lessons on Ohm's law (in France).
I thought this is how everyone saw these equations. Its crazy some people got through any physics or engineering degree without some fundamental understanding of these equations. Hats off to you! Must have required a lot more studying.
Have you never heard of a constant current source? Then, you need V=IR, since the current is constant, not the voltage. Also, have you never heard of a variable resistance? Sorry, dude, but you really don't consider ALL of the options. If you are a "rocket scientist" (isn't everyone at NASA?), then you understand about variable mass, constant acceleration, etc. right? Both of those equations need to to rearranged to suit the circumstances. Claiming that one form is more appropriate than another all depends upon the circumstances. Take care always.
That makes sense, however in highschool all we study is about a constant voltage source and a bunch of constant resistances. That's why we need I = V/R . The prior thing in schools should be to teach the way things work. Not how you plug in some numbers into an equation.
Doesn't a constant current source manipulate the voltage supplied, to meet the resistance and thus control the current? If that is the case, does it not deny that the voltage is the cause of the current? Just having a reactive system wouldn't meant that the causality was different.
@@LionKimbro A constant current source simply supplies a constant current, regardless of the load resistance. As the load resistance changes, so does the load voltage such that the current remains constant.
How do constant current sources work though? I had it in my classes, but never actually understood what are these. Voltage source are easy - we use it everyday in forms of battery. But I couldn't think of current source. Maybe some phone chargers? They often have let's say 1A charge current. But isn't it in reality the byproduct of voltage (from the socket)?
@@PinkeySuavo Well, without being an electrical engineer, as I see from your text, you just demolished @ulyssesfewl1059 approach :) A constant current source maintains current level by raising/decreasing voltage. Same for voltage sources with current. No matter how exactly they do it.
You're actually right. Understanding the basic fundamentals of the subject you are studying is really important if you're going to use it after you graduate in your job. I love physics, and I always try to understand the concepts, not just memorizing a bunch of formulas, and this understanding helps me to solve physics problems even if I have forgotten the formulas, like remembering concepts and then making the needed equation. V=IR was a good example, which a flow of electrons through a resistant material, doesn't cause electric potential difference because the movement of electrons itself has a cause which is potential difference, but it would be great if you also mentioned the capacitance formula: C = q/V so, according to the equation a student at the first glance might say, if we increase the voltage of a capacitor, the capacitance will decrease. But that's not correct! The capacitance of a capacitor is always the same and doesn't matter on voltage or the amount of charge. Instead, I would think that q = CV is better than the initial formula(C is constant value for a capacitor) to understand a capacitor. However, both formulas are correct if we don't forget the cause and effect.
im a third year electrical engineering student and i have never agreed with a video title more
These are Equations that are more general that functions. I think functions are useful when we want to see equation behaviour with respect to changing values of one term (variable). Since this is a monomial equation, F=m×a, F/(m×a)=1, a=F/m ... are all the same and each term could be assumed as function of 2 other terms.
However there are some more generalized forms of this equation in dynamics. For example in Mass-spring-damper model, equation is formulized for F. Considering time varying parameters we have:
F(t)=m.a(t)+k.x(t)+c.v(t)
In other words, each one of above terms are in form of Force (inertial force, spring force & damping force). Also since it is a diffrential equation (a=v'=x'', and v=x') we can not simply re-arrange and solve them as a(t)=F(t)/m-(k.x(t)+c.v(t))/m, since x, v and a are dependent to each other.
I'm not electrician but remember similar equation in RLC cirquits:
V(t)=Vr(t)+Vc(t)+Vl(t)
Where Vr(t)=R.i(t) is the simple form equation.
When discovered that coulomb's law is due to gauss's law but not vice versa , I experienced the same thing and understood how weirdly this world has arranged physics into our books 😅 I bet 19 of my classmates would even shock after knowing this if I tell them .
Great point Ali, as yo said no one teaches physics from cause and effect point of view. They just give you the simplest form easiest to memorize.
Never realized F=ma and V=IR similarities:
Both have an instantaneous rate of change with respect to time; I and a.
Both have a constant; m and R
@@oscarpesantes6342 Oh yeah, that is really cool. You helped me notice it.
F = m*dv/dt (constant mass)
V = R*dQ/dt
You can say they're all constant in Ohms law, because it really only hold true in a static case, an instateneous moment in time. Sure you can get accurate enough results for a circuit in "steady state" but if you've ever measured a circuit you will see that even the resistance value of a single resistor will fluctuate, even more so if you breath on it.
And actually if you really see it deep down and understand it...
Force is really just potential energy gradient (for conservative forces like gravity) and V is potential difference something along the lines of potential energy difference (for unit positive charge)...and so they both depict that energy difference cause motion in certain particles. And both actually accelerate the particle ... but in case of current we define the average drift velocity and so the acceleration of electron fades away from notice because of the averaging part.
So both eqns depict force fields that cause change in state of motion in particles like a normal object of mass m or a negatively charged electron.
Take a look at Bond-graph modeling paper
In the equation V=IR or solving for I we have I=V/R it is important to understand that I is a RATE; i.e., the rate of change transfer. The more appropriate statement should be that current is the rate of transfer of electrical energy. V is potential energy; i.e., Energy can be potential and kinetic. V (potential) is waiting for a path to be provided so that charges can move. Once a path is provided, the charges become a current; i.e., I = dq/dt. This insight allows for a rational interpretation of 'a' in F=ma as a rate as well. It is very important to recognize that the acceleration of a mass is analogous to a current flowing through a resistance. Conclusion: Study Calculus before Physics.
Clearly never done any electrical (and mechanical) engineering. 10:22 "resistance is already there, so the current is the product". Every non-linear device adjusts its resistance based on the current supply. Negative differential resistance devices struggle at hunting down the correct resistance value so bad, they become oscillators. But even theoretical electronics disagree with you. Many circuits use constant current sources where current is the input parameter. Their models are very practical for photoelectric effect simulations.
Same but worse with mechanical engineering. Nothing causes anything in mechanical systems. The 3rd law of motion and impulse preservation laws state that all effects are mutual, not causal.
This video pushes for using a worse form of the formula for an invalid reason. There is a reason these formulas are in the equational form and their transformation to a functional form is heavily context dependent.
But you need a voltage to produce that current
@@anghme28ang11 Nope. You can a have a current to produce a voltage. Electrical current is by definition the change of charge over time I=dQ/dt. You can move charge with a magnet and make them change over time hence creating a current.
@@glandeokrayo9956 I remember quickly moving magnet through a coil with a LED connected and making it blink, I felt like a magician!
How do current sources work though? I can imagine one as guy above wrote - using some magnets. But I can't imagine it in terms of battery or something.
@@PinkeySuavo most current sources are a voltage source modified to target a specific current. inductors are a true current source for a moment of time. inductive spikes are exactly when an inductor tries to maintain its momentary target current no matter the voltage. these spikes will physically damage any insulation in their way just to ensure the flow of some current.
Bravo! Very clear and demonstrative in real world dynamics. My chemistry teachers were big on application after the book learning. Every test had real-world application questions on them. I was already in my mid 30's and had the same mindset. If I felt that the class of the "kids" (just out of High School) sat there stumped, I would ask a question I already knew the answer to because it was on everyone else's mind and I didn't care if I looked stupid. The class often became a conversation between the professor and me while the others took notes. lol. Best student/worst student. I found it difficult to shut up and let other students engage.
Hi Ali, I’m a first-year electrical engineering student, and I’ve been searching for books that explain the underlying concepts in circuit analysis. In my course, we’re taught methods to solve for current and voltage in complex circuits, but they often feel like 'black magic'-given without explanation of where they come from or why we can make certain assumptions.
I’m also looking to understand how electricity works on a deeper, more physical level. For example, how do electrons actually behave when a circuit is powered on? How does the signal propagate in wires to create a specific current with a given resistance? And what is really happening across a resistor-are charges accumulating, or is something else happening? Proof of KCL and KVL, why resistors in parallel have the same voltage etc...
If you could make a video on this topic, recommending books that provide deeper insights into these concepts, it would be greatly appreciated.
The best person that I have seen to explain physic concepts is with Dr. Lewin at MIT 8.02 Electricity and Magnetism. Truly eye opening!
I completely relate with you buddy, same situation!
Proof of KVl? In university physics 2 you will realize that KVl is just Faraday’s law from Maxwell’s equations in a special case where the given system is conserved. Walter Lewin (MIT prof) further explains this in his channel. If you want to learn circuits study any university physics textbook (Freedman or Halliday are greats ones!). After that you could study electrodynamics (Griffiths)
KCL is ultimately based on conservation of charge. Charge entering a point = charge leaving a point, since charge cannot accumulate at a point (unless it is a capacitor, but just a point is not a capacitor). Even capacitors have their own conservation of charge law.
KVL is a special case of Faraday's law of induction. Essentially, when there are no inductive sources of voltage due to changing magnetic fields, electric fields are conservative. This means the closed loop work done on any charge, is zero.
"What is really happening across a resistor"?
Charge is not accumulating anywhere, rather the charge flow is competing with the thermal motion of the charges to proceed forward. The thermal motion is chaotic and adds up to zero among all the electrons, and is significantly greater than the electron drift. The electrical motion adds a slight bias in the direction of current flow that causes a net flow of charges. To overcome the chaotic thermal motion, it takes an electric field thru the component to bias the flow of charges to where they need to go. This means work is done on the charges to get them to move beyond what just their thermal motion is. This work done on the charges is what causes the voltage drop across the resistor.
"How do electrons actually behave when a circuit is powered on"?
The electrons already fill the circuit. The electric field propagates at nearly the speed of light through it, and disturbs a large quantity of electrons at once. This causes them to no longer just move randomly for their thermal motion, but also to move in the direction the electric field forces them to move.
One of the most remarkable parts of this question, is that the electric field propagates, even where there isn't a wire. Derek from Veritasium has a thought experiment about this, where there's a battery and switch, that's 1 meter across from a bulb, and a circuit that extends 1 light second in both directions. His question was how long does it take the bulb to light? 1 second? 2 seconds? 3 nanoseconds? Or 1/2 second? The answer surprisingly is 3 nanoseconds. The electric field actually propagates across the 1 meter gap first, and causes current to flow through the bulb, before it can even complete a round trip through the circuit. It doesn't sustain significant amounts of current, but current flows nevertheless. You need to complete the circuit to maximize the efficiency of power transmission, but you can still transmit small amounts of power, before a round trip is complete.
Alpha Phoenix has experimental evidence that supports this theory. He constructed this thought experiment with a kilometer of wire, and a load that was 1 meter across from the source and switch. He tested it with a state-of-the-art oscilloscope, and showed that you get power transmission faster than the round trip time for the circuit. You don't get full power transmission until the round trip is completed, but you still get some power transmission in the time it takes the field waves to propagate just 1 meter.
Thank you! Would love to see more videos from you
Glad you liked it!
Sorry Ali, I have to quibble about V=IR. There are lots of places in electrical engineering where we use constant current sources and current mirrors. So, unlike the familiar battery, which provides a (roughly) constant voltage, these circuits provide a constant current, and the voltage generated across them depends on the resistance you place in the circuit, so V is indeed caused by I and R, or V=IR.
To drive an LED, you don't control the voltage on it, but the current through it - if you ask "what voltage do I need to drive this LED?" and then pick a voltage supply equal to its forward voltage drop, part tolances mean you could drive too much current into it, or even kill it as temperature goes up - as diodes conduct more as temp increases, and "I" is an exponential function of V and T (temperature). To design a proper LED driver, you ask "how much current do I need?" and pick an appropriate resistor for your voltage supply, which can be anything above the diode(s) forward voltage drop. (But this assumes you're using a battery-like supply, and not a constant current driver). So although the current does develop a voltage drop across the diode, thinking of that as being "caused" by the battery/voltage applied by the power source doesn't help you pick the right resistor for the circuit.
Arguably though, a more interesting equation is V = L * di/dt. This equation DOES follow your causality notion as it is, but not in the way most people expect. If you've unplugged a vacuum cleaner while the motor was still running and seen a bright spark at the outlet, you've seen this equation in action. The "V" in this case is NOT the voltage at the outlet (120V in the US, 240 in other parts of the world). Unplugging the outlet quickly decreases the current in the motor - and since the motor is a bunch of inductive coils, they each have an inductance "L." That sudden drop in current (di/dt) means the energy stored in that inductor will suddenly create a high (negative, compared to the way the inductor was just powered) voltage large enough to break the resistance of the air, and create a high-voltage spark between the outlet and the plug. That spark can easily be over 1000 volts, as is the voltage across the inductor as well.
don't you think that a current source is just a closed loop circuit that is constantly monitoring current and adjusting voltage?
@@alithedazzling A current mirror acts like a current source, and doesn't use "monitoring" of a voltage - i.e. no feedback measuring output current and adjusting it.
Even though this is the way I think about these topics, watching this made me realize how important it is to give these intuitions to my students
I always teach my students to think of ohms law in 3 ways depending on which term it is expressed in:
V=IR - Ohms law, V is directly proportional to I if Rbis constant at a constant temp
R = V/I , defining equation for Resistance and what is meant by an Ohm.
I = V/R , the only format that (as you say) expresses the causes and effects on each side of the equation. We don't change current to change V or R, but if we change I it is only because we are also changing V and/or R.
I think all three ways are needed to help students fully grasp the idea of thinking deeply about core concepts.
Side note: your casual use of language had me concerned. Current is not a flow of charge, it is the rate of flow of charge for example. You also mentioned speeding up the Voltage, that is a big cause for an effect of misconceptions.
So what is a flow of charge then if not current, what would call it?? When you want to express the rate you use units of amperes (coulumb/sec) to quantify the rate, amps is the rate of the current.
Not to nitpick you, but please explain how what I've said here is incorrect if you disagree.
@onradioactivewaves electricity is a flow of charge in which there is a current. But the flow isn't the current, but a sign there is a current, if that makes sense.
In truth the difference is subtle and to most it isn't a problem. But if you are studying the topic an exam will require the correct use of the term.
@@dakeyrasuk I have studied it and I've also worked in an electrical field (no pun intended) where many terms were commonly used interchangeably and incorrectly. The word electricity is pretty generic and can mean many different things, but in general can be assumed to mean pertains to electrical charge / energy. Current can take one many different forms/ meanings as well. It could be drift current, AC or DC current, dispersion or diffusion current in a semiconductor. These all had very precise mathematical definitions when it came to exam time.
I kind of get where you're coming from, but the same general word can have very different meanings depending on the context. One person saying electricity could imply charge flowing in wires, in another context it could be referring to a static charge causing a persons hair to stand on end no current involved. Unless in a particular context or more technically described, general terms can be very ambiguous. I might use electricity instead of current if talking to 4 year old, whereas saying current in regards to a semiconductor without any other context could be nonsensical.
I've had these discussions with professors, students , engineers, many of whom do not speak English as their first language ( technically not my first language either) At first this was difficult for me, but ultimately forced me learn how to communicate better technically and precisely (I've also had to read and write plenty of technical documentation). So while I can agree with what you've said, there's always going to be different interpretations.
I agree, but there can also be the other approach of writing the equations in the order where things were defined.
For V=IR, what actually happened is that scientists saw that you take different materials and put them under voltage, and you get different currents, which led them to define resistance as R=V/I. So your equation can either say "voltage causes current according to resistance (I=V/R) or "resistance is defined as the ratio of voltage to current in a material".
For kinematics, mass and acceleration are easily measured, and the force was defined later, so F=ma is the way to write it under this style.
8:24 "It's really something that breaks my heart" 😂😂
Intuitively it makes sense to me as well. in my current understanding, emf and resistance are properties of the battery/components that can be tested in isolation and won't change based on the circuit it's put in, but current isn't exactly a physical property that can be tested in isolation and can only be derived from the situation of the circuit.
I really expected more from this video like diving deep into what current, voltage and resistance really is and how they truly relate. This more fitted for high school students. I like your thinking pattern but it's to general for my taste.
I don't mean to sound arrogant, it's a good video and you are a good teacher, I was just hoping for more.
The point of this video was to teach the basic concept, It was not meant to go in detail. If you had paid attention from the beginning you would've known...
@@mindhunter8772 I meant what I expected from reading the title and seeing the thumbinail.
Nice video and presentation.
This is the first teacher on UA-cam who appreciate and teaches the importance of “cause to an effect” relationship.
Oh the I = V / R makes a lot of sense
ربي يجزاك كل خير أخي علي و بارك الله في علمك ❤ لو من الأمكن إنك تنزل ترجمة عربي لتعم الفائدة على فئة اكبر ❤❤
disagree… voltage is not a force
It is not a force as in mechanics, but it is an impetus. But when a given impetus exists, does the flow of electrons ever fail to equal the potential flow? Well, yes, as in inductance or capacitance. So it may be like the flow of water down an inclined plane, with little traps occasionally for the water that slows it down more than just the angle of the incline.
OMG! It's the first time that even physics makes logic or else in our school we are just taught to plug in some random numerical and the better you are at it, the greater marks you will achieve. Thank you so much for making a great video, eagerly waiting for more of this kind.
bro is onto nothing
Interesting perspective. Our physics teacher at school liked to write the 3 symbols of these kinds of relationships in a triangle e.g.:
V
I R
So you remember that and can generate any of the 3 equations you need, there's none of the "this is *the* variable we want to calculate" suggestion that you talked about.
Btw the causal relationship isn't so clear in electronics e.g. if you connect a photodiode (or even just an ordinary LED) to a resistor and shine light on it, it will generate a current, and you can measure that current by the voltage across the resistor, so V = IR.
I have electric circuits in my course and the way you have explained on WHY and HOW these things work really made my concepts clear
And I think people will actually be able to relate with these concepts if they visualize it themselves rather than memorizing the theory
And honestly visualizing these things is what makes Physics more interesting and fun to learn
I'm so glad to have watched this video
Thanks :)
The way I understand V=IR is actually to say if you have a load resistance of 10 ohm and your circuit must be able to draw 2 Amps, you will need at least a Potential difference (Volts) of 20 Volts to achieve your goal, but definitional wise to explain the equation, yours makes much more sense!
This is related to directly proportional... Like if a man fall from the top of the mountain he will get hurt. But if another man got hurt it doesn't mean that man felt from the top of the mountain. So here If someone fall from the mountain he/she will definitely get hurt. If someone is already wounded it doesn't mean that person has fallen from the mountain.
For the past four years when I was studying engineering, I was always thinking about the same thing that you said and that video we need to look at things in terms of cause and effect and reason I'm so happy that finally someone pointed that out
This is a great way to put it, I really enjoyed the explanation.
I have a bad effect of hypersomnia while studying. But your teaching methos kept me focused & beat that thing. Thanks sir. Eager to learn more from you.
Thank you.
Hewitt is the only other who explained it similarly and I much prefer this. It finally made sense to me. I plan to use this.
Glad it was helpful!
Sir hats off to you!
I am familiar with both of these equations but never thought of such understanding. Now I feel superior in my classroom after knowing this and i have also made sure that my friends are amazed too. Going to be a high school student soon and I will be pleased to dedicate myself in learning more concepts from you. Love from India 🇮🇳
I think your video highlighted some really good points about how current plays an important role in circuits. But I believe what's even more crucial is the interworking of energy-specifically, the potential difference. The voltage in a battery comes from the potential difference created by the electrochemical reactions inside. For instance, a standard alkaline battery gives 1.5 volts because of the specific chemicals involved, and when you combine multiple cells, their voltages add up. That’s why you often see batteries in series to achieve higher voltages (like 3V or 9V).
When it comes to the structure of a battery, multiple cells are combined to increase the total voltage, and this organization creates that "hunger" for electrons to move from one side of the battery to the other. The size of these cells is directly linked to battery life, or capacity, because larger cells hold more chemical material, which in turn allows for more energy storage.
Regarding voltage drop, the voltage stays relatively constant during most of the battery's life. It remains steady until the energy is almost gone, at which point the voltage drops rapidly. This happens because the battery can no longer sustain the chemical reactions at the same rate as before, leading to that sharp decrease in power output.
As for **resistors**, they are made of materials that prevent electrons from moving through them very quickly, kind of like plugging up the flow of the battery’s discharge. The pressure (voltage) from the battery remains the same, but because of the resistor, the energy cannot discharge as quickly. In other words, the resistor limits the current, so while the battery’s energy is still there, it’s released more slowly. The energy loss that happens in a resistor is converted into heat, which is why resistors can get warm during use.
One thing worth adding is the role of **resistance** in this process. As the battery discharges, internal resistance tends to increase, which can further lower the voltage output as the battery ages. In circuits, external resistance also determines how much current flows for a given voltage Ohm’s law: V = IR meaning a higher resistance will limit current flow. So, battery life can be affected not just by the capacity but also by the resistance within the circuit it's powering.
In short, voltage stays relatively steady, the capacity depends on the cell size and chemical composition, and resistance plays a critical role in how much current can flow and how long the battery will last before reaching that rapid drop in performance.
❤ u
U r the first UA-cam teacher I have sseen ever to explain in depth.
Sometimes, in electrical engineering, we have a constant current and we have a target Voltage, so we need to solve for R. Old school Ammeters gauge a current through a known resistance and that is how we measure voltage. Plus, once you start adding inductance and capacitance into the equation, physical analogues start to have less utility.
I'm not saying this is wrong or that no one would benefit from this line of thinking, but I think most EEs would prefer to think of V=IR as simply a relationship between electrical properties... Just my opinion - I could be wrong.
Thank you for the real perspective 🙂
Yep, i totally agree with this, and i've of it myself just a few weeks ago. It's far easier (and it's how i've been understanding anything in physics till now) to see a formula as a rule of causality, with the cause and the effect. It's not necessarely the truest way but it's definitely the one we can understand.
An equation can be seen in many different ways. The cause and effect can be other way round too if we start talking in that way. But you're correct in mentioning that causality brings life to Physics. 😊
WOW. Glad I stumbled onto this.
I wondered where you were going with this at first and you take too long to get the the root of the issue - cause and effect.
From comments saying they never thought of cause and effect, tI can see they have indeed, learned very poorly.
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You are on to an important point that I have seen for quite some time. The cause and effect is VERY IMPORTANT and if that isn't taught any more, that is very sad, because it isn't teaching.
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The equations NEVER show cause and effect. They ONLY show what happens - not why.
Which are dependent variables and which are independent variables.
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In the beginning. When scientists study things and provide equations:
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The physical behaviors are understood FIRST.
THEN.
They learn how to quantify the values.
THEN
Then find the equation that mimics the real, physical world.
THEN
Then,
We can use the equations, but we must understand the underlying physics to use them correctly.
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The equations are a model of the physical world. Equations do not define the behavior, nor control them. They are a tool that imitates the real world's values.
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Advice. . .
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For one thing, F=MA starts when the guy PUSHES On the ball. His force accelerates it horizontally. The slope and gravity complicate it more than necessary.
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Then, Mass resists Acceleration. The fundamental, physical property we call Inertia can be said to describe that resistance. Let's teach that!
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I have felt for a long time that we need to re-describe Newton's Laws of Motion because too few truly understand what they really tell us. I think it is simply a desire to retain Newton's words, but the real meanings are also lost.
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Newton's First Law tells us that Force is the CAUSE of ACCELERATION.
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The First and third Laws tell us that Inertia resists Acceleration and that 'resistance' is why there is what he calls the "reaction". Therefore, we can say that Inertia is the Cause of the Third Law 'reaction'.
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I've seen beginners confuse cause and effect from the wrong interpretation of only the equation.
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Seeing others say they didn't consider cause and effect is very sad.
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Perhaps this is why I have seen some so-called engineers that don't really understand their subject.
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From an experience engineer.
I am actually greatly inpressed by ur teaching skills
I thankful my teacher taught me that way. The original formula is I = V/R which actually is Ohm's law. The V=I*R and R=V/I are byproducts of Ohm's law. Also as you correctly said, we are not changing the resistance nor the battery meaning that they are stable, so the I is dependent on those and to be on a closed circuit. Change the battery with lower volt, the amps will charge, the resistance will not. Change the resistance, the amps will change, the volts won't. So I'm really thankful my teacher taught me how to think. And I really love your video. It makes us think.
Thank you ali for this video i really admire your passion for engineering
Cheers Ali ! I haven't ever looked to physics equations this way , now it makes much more sense,
If only teachers used this way of intuition in Iraqi schools .
my physics teacher actually taught us about the cause and effect in Physics which really grows on me and thinks more about what the idea behind each equation is. Beside I like equation in their vector differential form lol (or integral) because it just give you so much more understanding (and able to solve non uniform problem)
I love the message of this video! When I was learning kinematics in high school, our teacher simply gave us a formula and told us to plug in known values to solve for the unknown. That’s it. There was no intuition or explanation of how and why the formula worked to calculate projectile position, and this really bothered me. I decided to start from scratch and derive the formula myself using my intuition about velocity, acceleration, etc. I eventually came up with the same equation the teacher originally gave us, but my version was factorized and allowed me to see exactly how the individual terms worked together to show projectile position, and why the final equation looked the way it did.
Do you have any possible resources you could suggest using? I’m having the same exact problem right now and am also trying to balance teaching it to myself from scratch
@@Milkenj0yer So far, the most helpful resource for me has been Khan Academy. It has a vast number of video/reading lessons covering many courses ranging from kindergarten to the college level. All the lessons have easy to understand explanations and illustrations, and they also provide quizzes and practice problems that help you progress your knowledge through the course (and everything is completely free). I've also heard of an app called Brilliant that teaches math and science through interactive lessons, which helps with intuitive understanding of concepts. However, I can't speak from experience since I haven't tried the app yet, but it seems to have a very positive reputation among users.
@@Milkenj0yer So far, the most helpful resource for me has been Khan Academy. It has a vast number of video/written lessons covering many courses ranging from kindergarten to the college level. They always explain topics thoroughly with illustrations, and provide quizzes that test your knowledge to help you progress through the course as if you were learning it officially with a real teacher (and it's all for free). I've also heard of an app called Brilliant that teaches math and science using interactive simulations/lessons, which is really helpful for building intuition and deep understanding of concepts. I can't speak from experience since I haven't tried the app, but it seems to have a very positive reputation among users.
@@Milkenj0yer So far, the most helpful resource for me has been Khan Academy. It has a vast number of video/written lessons covering many courses ranging from kindergarten to the college level. They always explain topics thoroughly with illustrations, and provide quizzes that test your knowledge to help you progress through the course as if you were learning it officially with a real teacher (and it's all for free). I've also heard of an app called Brilliant that teaches math and science using interactive simulations/lessons, which is really helpful for building intuition and deep understanding of concepts. I can't speak from experience since I haven't tried the app, but it seems to have a very positive reputation among users.
@@Milkenj0yer So far, the most helpful resource for me has been Khan Academy. It has a vast number of video/written lessons covering many courses ranging from kindergarten to the college level. They always explain topics thoroughly with illustrations, and provide quizzes that test your knowledge to help you progress through the course as if you were learning it officially with a real teacher (and it's all for free). I've also heard of an app called Brilliant that teaches math and science using interactive simulations/lessons, which is really helpful for building intuition and deep understanding of concepts. I can't speak from experience since I haven't tried the app, but it seems to have a very positive reputation among users.
Such a good video and thank god someone has posted it. I have been teaching Physics for over a decade but students just don't get it when I say, "we are doing physics, not maths."
However, I agree with a=f/m but Ohm's Law is best explained as R=V/I and current as I=Q/t