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- Опубліковано 29 сер 2024
- Fundamentals video explaining the difference between voltage, power, and energy. The difference between Power & Energy is probably the most misunderstood and misused terminology in engineering!
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Sometimes when I look at old devices I find very clever circuits. Simple and elegant. Can you make a video on the most ingenious circuits you have seen?
Upvoting this request.
@@DesignEngineeringChannel Samesies mofos. I'm def feeling that. Somebody not on mobile make and take /r/EEVblogCircuitPorn so you can give creds to the man so he has a spot to drop the goods.
Dave please do a video explaining impedance. So many people are not familiar with the idea of AC resistance.
AC in resistance has a lot of steps for learning, impedance goes hand in hand with capacitance you must learn them both, and before that you need to understand sin waves and phase. It's very interesting topic but it's not something you can jump right in with out explaining the other basics of AC first.
ac impedance is finicky though ... but the best way ive learnt to understand them is vector diagrams
Good ol' ELI the ICE man!
I think electronic engineers focus too much on the maths. Look at the physical reality of systems and why they behave a certain way. e.g. why do inductive loads raise impedance and draw current lagging voltage? Why does a capacitive load drop impedance and draw current leading voltage? Then later you can learn the maths to apply the understanding to each new scenario.
And they turn a lot of people off from pursuing the field of electricity. A good teacher would teach practical concepts (how things actually work) then bring the math on (as little as actually necessary) as the student gains a working knowledge. You can do a hell of a lot with electricity with just ohm's and watt's law. Not everybody needs engineering level math to do their jobs.
Finally the proper explanation. The perception of any of the 3 is always so wrong and in what I do when I try to explain the differences people get even more confused.
Thank you so much you are the best... ;-)
Can you do a video on the basics of True vs. Reactive vs. Apparent Power?
+1
i++;
while(noPowerVideoExists) { i++;}
Edit: Just thought of something after seeing the Google images beer analogy. Is there a difference between a direct short vs offset ø = π/2 radians? From what I see online, an offset of ø = π/2 radians is the same as having a capacitor directly across the AC terminals. So after π radians when the voltage begins to reverse, the capacitor will begin to empty back to the source because of the polarity swap at the AC terminals.
I never quite got what reactive power really was until I read about that scenario with the cap across the AC terminals. Kinda makes sense now. Just thought I'd share.
u really want him to cornfuze u?
+1
Photonicinduction's comment sections are usually full of people asking how high his electricity bill is. The fact is that it's barely different to a normal one, as his high power experiments do not run for a long amount of time, and don't run up a high cost as electricity is charged for in energy.
Yeah, good example of energy usage.
Dave, WELL DONE! I've been an electrical utility engineer for 43 years, and I'm constantly amazed that we produce new engineering graduates that don't understand these concepts. Half can't explain the difference between kW and kWh.
Now, since you are on a roll, trap for young players. Explain the difference between real power and reactive power. Heads will explode! Great video!
Bill Moran Really? People can get engineering degrees without that being so engrained into their head that it's intuition?
That's like, first year EE bullshit classes stuff.
@CODMarioWarfare what prompted this video was a video I saw of a graduate student saying that voltage was energy!
I am not an expert physicist, but my common sense tells me that voltage is a measure of potential energy( per unit charge). When you say that we can have voltage without energy, I dont think so. Static energy is a small amount of energy. But it is energy. Voltage is not 'energy' just like power is not energy. It is rather the energy per unit charge and the energy used or produced per unit time respectively. But they all mean energy, although a specific or more accurate way to describe that energy.
I agree with "When you say that we can have voltage without energy, I dont think so". this example is not so accurate. If we have huge voltage from static electricity that means we have lots of energy but few charges and this coincides with a big voltage with no current that doesn't kill.
CODMarioWarfare first year EE BS stuff is the foundation of engineering. The problem we have is people who got a degree but don't actually know anything they should have learned. The degree means nothing. It's what you learned that counts.
AvE would have said Voltage is how angry the pixies are at the door, and
Current is how many of them are running through your house after you
open the door. Energy is how much damage they do in the process, and he'd be done already.
Power would be the damages they are currently doing. Energy would be how much they have done over a period of time, to untill they get exausted. If you stop them, they won't cause any more damage, but they still have the remaining energy.
I find this more accurate than Daves explanation which ignores the concept of charge. As he waved his hands at, Voltage is the energy each pixie has...the more pixies that flow, the more energy is carrived by the pixoes per time which means more power and more skookum chooching...
Landrew0 👍AvE!
The pixies are the current, the charges. The voltage is what move them around, the potential difference between two points.
I guess pixies are no easier to understand than Watts and Joules/s defining each other...
The "pixies" is just an other way trying to explain Ohm's law anyway, not trying to explain power and energy, imo.
So what happens if Hodor holds the door closed?
Even though i majored in Automotive and became a mechanic. I have always wanted to be an Electrical Engineer. SUBSCRIBED.
EEV videos with a whiteboard are the shit. Great stuff.
I've always explained to little kids that voltage as the pressure that is pushing on the electrons to move, current is them moving, energy is the effect of what happens to the thing they move through and power is the rate of the effect.
AvE would have said Voltage is how angry the pixies are at the door, and Current is how many of them are running through your house after you open the door. Energy is how much damage they do in the process.
Stephen Low i think of voltage in like strength (the 'amount of pull' on the electrons)
And power is you watching them smashing things every second!
Except that the electrons don't really move that much. They certainly don't flow from one end of your circuit to the other at the speed of light, like you think they do. :)
Electron always had this trouble of moving thru materials, all the atoms jostling around is blocking & slowing them down... but as an electron is pushed forward, its neighbour in front of it senses this and made his step forward as well, and it chained with next neighbours making a general step forward too, and it result in electrons marching forward... this electron centipede allows electric current to be transferred at near light speed.
You are a good teacher, Dave.
EEVblog - Thank you so much for this video. It gives me something to refer people to when having exactly these arguments in UA-cam comments.
It's amazing how many people talk about this stuff, probably thinking how clever it will make them look, but it just makes them look ignorant.
Very informative video. Thank u. But I wish that you could have also included the difference between voltage and EMF.
I think Dave was aiming this at folks with little-to-no prior knowledge of the subject, and trying to confer an intuitive understanding, rather than a strictly rigorous treatment. If he were to start at the beginning, define all the fundamentals, and scrupulously define the discussed terms, it would take a semester, and even wrinkly brains would explode.
Well done in the allotted time, and for the intended audience. How many Angels can dance on the head of a pin, guys?
Well.... that was clear... must say that the analogy with the dam made it even more clearer... thanks...
So much for the previous comments. I still enjoy your explanations and visual examples Dave. This is what drew me to your channel several years ago. Your tear-downs , teaching electronics , and "Down under " comedy. KEEP GOING Dave.... J K in Texas
This is one of the best explaintainment out there. It adresses all the aspects of the topic and as a non english speaker I love the 'strayan "hoay" part!
A seppie here with an Aussie wife. When we, um, ~talk~ about a cupboard vs a closet, or a tram vs a pram vs a trolley vs a cart (shopping)... well, it sounds quite a bit like what you just said. I know you are not wrong, but I still might say it different and still know what I'm talking about. Hope you enjoy the comment in the humor it was meant!
마지막 댐으로 비유한 것이 아주 적절하네요.
전압은 수위의 높이,댐에서 흘러 나가는 것은 파워,댐에 저장된 것은 에너지..
You're the only reason I know anything electrical.
You just explained far better in 10 minutes what took my professor over an hour.
Dave you're the best electron dompteur. Thumbs up and keep going!
Not sure why I watch this whole video, as this is pretty basic stuff that I learned several decades ago. But good on you Dave, everyone who knows this stuff has to constantly be educating people about how the universe runs. You might want to add that energy can not be created or destroyed, only converted from one form to another, google conservation of energy, then google thermodynamic laws, once you have all that down your well on your way to being enlightened!
I'm a Chemical Engineer and this always confuses the $hit out of me. Thanks for the video.
Would be great to see a vid about the difference between watts and VAs.. I never got my head around apparent power
I don't know the full answer to that, but I do know watts is the real power and VA is apparent, and often seen with AC.
Think it's because AC it would be the average, since the current and voltage fluctuate and change polarities.
Dyexmax, what a load of crap, just shut up.
this is correct, VA is apparent power when measuring for AC. but it's also active power when measuring DC, that's where most of the confusion comes from beginners.
I think of reactive power this way: Powering a purely resistive AC circuit is like riding a bicycle from point A to B on a flat road. You're the generator. Your pedaling is easy and constant. Powering a reactive circuit is like riding a bicycle from A to B on an undulating mountain road that goes up and down, but ends up at the same place as the flat road. You put more work into going uphill, and less coasting downhill. But overall, you worked much harder to get there, but it wasn't useful work. That extra work that didn't get you anywhere extra is like reactive power.
I remember the relations between them as a right triangle. The adjacent side (that's the base of the triangle) is real power, measured in watts. The opposite side (or far side of the triangle) is reactive power in VAR. The hypotenuse (long side) is apparent power, in VA. The angle between the adjacent and the hypotenuse is the phase angle difference between the voltage and current, and the cosine of this angle is what they call the Power Factor.
When an AC load is purely resistive (the voltage and current waveforms are in phase), the angle is 0 degrees, the power factor is 1, and the triangle is flat. The hypotenuse is equal to the base and there is no opposite side. In this case VA=W and VAR=0 so there is no reactive power. Everything you generate is used by the load.
As soon as you add any reactance to the circuit (typically the coil in a motor or a transformer), the voltage and current go out of phase, the triangle's angle increases, the power factor goes down (the cosine of the angle goes down), the hypotenuse gets longer compared to the base, and the opposite side lengthens and you have some amount of VAR (reactive power). Reactive power simply shuttles back and forth, doing no useful work in the load, but causing your generator to work harder. Because of this, VA is always greater than W in a reactive AC circuit. W is the work done in the load, VA is the power required from the generator, VAR is the extra work that doesn't get you anywhere and is wasted.
This would be much clearer with a picture of a moving right triangle.
Great job, thanks for correct explanation. Honestly I forgot all about VARS since it's more impotent in AC and just could not remember it until you started talking about phase and right angles, it's been a while.
That multimeter demo really drove the point home. Awesome explanation man
Not really, since instantaneous is a measurement of time
nigga chill
Nice one Dave. Nice to have a reminder every once in a while.. This stuff takes me back to my college days some thirty yrs ago.
Just wanted to say that I wish I could double sub you, Dave. Your explanation was very good. The concepts of energy, power, voltage are very clear as you explained it (at least clear to me). Hope you do more of these types of lectures that digest first principles. You'd be amazed how more clear you sounded than most high school teachers or even college professors. I do have to admit that for people to more comprehend what you've said that they also have to know current (and therefore resistance as well), but I see why you deliberately chose not to delve into that.
I had high hopes for this video :) Most people understanding the first part of the video already knew the difference between Power and Energy (most likely). While something like the last part of the video where you made the water dam analogy will have been most useful for those not understanding the difference between power and energy.
Starting with the water dam analogy maybe even adding one or two more analogies will have had a better impact (I think).
Excellent refresher.
Great explanation! One slightly under-represented point is when you were talking about Amp-hours at the end. Amp-hours basically just count electrons, and that is why amp-hours (Ah) are incredibly useful when talking about batteries because that is really all that gets moved around chemically in the battery. Since electrons aren't gained or lost through resistance or heat (etc), it is a very useful unit of measure for a battery. Even when a battery loses capacity with stress and age, it simply means that some of the electrons get bound up in chemical structures in ways that make them unavailable to the circuit. They aren't actually lost.
On the flip-side, lots of those little USB power-back makers advertise their capacities in mAh, but decline to mention what voltage of the underlying battery pack, and so intentionally misrepresent the actual energy content of their power packs.
This reminds me of another little snippit... you know all the silly hype about those "nuclear batteries". Its easy for the nonsense-pushers to talk about tens of thousands of years of energy and replacing EV batteries with "nuclear batteries" when they neglect to mention that such batteries put out so little power you'd need millions of them to generate enough to make an EV actually go anywhere. Oops!
Thanks sir Dave.
God bless you.
Brilliant Dave! I knew all of this, but somehow I hadn't twigged that mAh ratings are not a unit of energy stored in a battery. I totally didn't think about the voltage drop.
Is not just about voltage drop a NiCd battery has a nominal voltage of around 1.2V while LiCoO2 cell around 3.7V so if they have the same Ah rating they will have quite different energy storage capacity.
Thank you! I think you taught me more here than I learned in one year of high school. ;-) Maybe teachers assume that you just know what the terms mean without making sure that everyone is on board.
Love the clear explanations of what can seem like a tangled web of misnomers
You have a lot of positive energy! If only my uni lecturers were like that.
What a Power-ful presentation. I felt Energized by the Time you finished! Say Watt?
That's slightly better than #1, but me thinks you still have got to do a revision #3 of this... :-)
Gives a whole new meaning to the phrase 'with great power comes great responsibility' while makes 'i have energy' more appropriate than 'i have the power'
But makes you think, if power companies should be called energy companies instead
Another great video. Great man. Thank you!
This is great video. But I do have one concern: Power is over time - a rate of transfer. Jules per second. When they say Watt Hours, its kinda a redundant multiplication then division.
I think Feynman said that he thought all the different ways of measuring energy was silly. Thanks for clearing this up for everyone.
Lad nogle flere af de her videoer, du forklare det så alle med lidt omløb i hoved kan forstå det. tak.
Good video Dave. I'd give it 4 out of 5 stars. I LEARNED SOMETHING, that's the main point!
Hi Dave you have absolutely amazing energy, would love to know your dietary views as well someday which keeps you that motivated
I always compare power with speed. If you say km/h, you do have that hour component, but the actual speed is a property you have right at that instant.
Yeah.. power is closer to motion/time. The motion itself is the power, which is created by energy to begin with. Per hour & instantaneous are the same thing - measurements of time (motion)
Although the stuff in this video is baby stuff to me and would usually be boring, EEVblog is always very satisfying to watch!! Keep it up!
excellent explanations sir .
Being the pedantic physicist that I am:
at 2:10, the reason for this is that both voltage and energy go roughly the inverse of the size of the object (works well with spherical humans). A capacitor being so small you can have lots more energy for the same amount of charge.
This is also why we use the Earth as a voltage reference, it is so big might as well not have any charge, i.e. 0 volts with reference to the rest of the universe.
"A capacitor being so small you can have lots more energy for the same amount of charge."
energy?
The smaller the capacity of a capacitor, the smaller the stored energy. If you charge two capacitors with a given amount of charge Q (=I t i.e. Current times time), then the capacitor with the smallest capacity C will hold the biggest Voltage difference V: i.e. V=Q/C or C=Q/V (units: Farad=Coulomb/Volt or )
The potential energy stored in a capicitor W is equal to the Capacity times the Voltage squared divided by 2: W = 1/2 C V^2
I wonder if I can use MathML to insert equations in the comments... I will try:
C×
V2
2
Q=I×t
V=QC
edit: it doesn't work :-(
@@spc67h E=Q^2/(2C)
For the same voltage smaller capacitors hold leas energy however, yes.
Thanks for another great video Dave :)
Since you used Volt=J/C and Power=J/s, why did you not mention that Energy is measured in Joule?
To further this damn analogy, the gate is like the resistance of the circuit. The dam while closed has infinite resistance (so no current flow, thus no power flow). When the gate is opened, you're reducing the resistance and allowing current to flow, thus allowing the power to flow.
Also, as you said, the water right out the gate isn't really power. What the ground or receiving end of the flow sees is the power because the water has made the trip though the voltage potential (height of water when current started to flow.)
I wouldn't say infinite resistance
It might be illustrative to note that the instantaneous speed of a car could be 60 miles per hour even though the unit has a time component. Come to think of it though; I've never heard of a mile hour either. Anyway great video Dave!
Thank you so much. A crystal clear understanding of the three terms!! Please do a video on passive sign convention with regard to Power measurement in Circuit Analysis.
14:39 I think the rate of flow is the current. The power is the umpf of the impact when the water hits the ground.
Anyway, the other day, my 6 year old got a small static discharge when touching me after riding a plastic slide. He was amazed and we got into talking about current and voltage. I explained it like this:
"Voltage and current is like a stone falling on your foot. The height of the stone is the voltage and the weight of the stone is the current. The static-discharge-lightning-bolt just now is like a tiny-winy pebble (or lets say "a feather") dropping from very very high. It didn't really hurt, because although there was lots of voltage (height), there was almost no current (weight). If you lick a battery (i.e. those 9V block batteries), you feel some dizzle. Not a problem, its like if a stone drops on your foot from 1 cm height. Its quite heavy (can have quite a current), but its very low voltage.
But don't play with the wall-plug power supply. That would be like standing on the street and a big rock hitting you from our balcony!"
I think he got it. He promised to stay away from the wall plug :-D
About time this was explained
The unit of "energy" is the "Joule" & that would have been better than using "kWh".Then V=J/C W=J/S & enery in J.
What a great video you produce, thank you for making interesting instead of putting one to sleep. Keep making video's please.
I know that Peukert's law primarily affects lead acid batteries, but do the principles of Peukert's law apply to your comments at the 10:20 mark?
Dave, on the matter of teaching, I just remembered something. A while ago you reviewed an industrial IO adapter for the RasPI, and I remember you marveling about how those I/Os were properly voltage and current limited for industrial use. Could you do a video on how to actually do that, please? That is, how to "Industry-proof" µC I/Os, or devices in general, with proper U and I limiting and anything else you said back then? Thank you
Yes, the mAh figure is not a measure of energy, but you've got to keep in mind it's a figure given next to another figure: the rated voltage of the battery. So that if you see a 1.5 volts battery that is rated 18Ah means it's got a capacity of 18[Ah]*1.5[V]= 27 AVh = Wh (watts=volts*amps). That's how you make sense of it.
OMG i wish you where my teacher at high school. You are so good at going down to a "dow" level
Two people got batterisers. Voltage is a scalar magnitude, Power is a scalar dependent on the vector of Time, Energy is the unit upon what is based Voltage and Power.
Thanks for the video Dave! I think we need you to make a video that explains what power factor is. I find explanations about power factor on the internet a bit confusing.
I gonna link this video in every online article of a tech journalist where they mix it up
In these parts, the electric system operators, regulators, and everyone reporting on it need to watch this video. I don't know how many times people who ought to know better have said stupid things like "X MW/day". Megawatts per day? What? Maybe they mean "we were generating X MW on Y day" but then they should actually say that!
Good explanations. This is hard stuff to cover, especially all at once like this.
I really liked the classes Congratulations
Always having a hard time seeing V for voltage instead of U. Is it only in the EU that U is used for voltage?
Interesting, did not know that. We use E and V for voltage in the US.
Europe is correct. It's retarded to use the same letter "V" for voltage and volts!!!
So you have for example 5 volts. American will write: V=5V. That's plain stupid.
Letter "E" is way better (and it's sometimes used in Europe too).
E is normally used for energy [J or Wh] or electric intensity [N/C=V/m] (to speak for my experience in Germany), I never heard of E for voltage but I have to say I'm just a mechanical engineer :)
Using E is illogical. E for electromotive force (aka. voltage), E for electric field strength, E for energy, E for irradiance. How much do you want to overload poor E with more or less related quantities?
ppdan here is something our professors say: there is no conservation of letters law.
As physicists we use all sorts of notations. U for potential in lagrangian mechanics, V for potential in quantum mechanics. Φ for scalar potential in electronagnetism and fluid dynamics. A for 4-vector potential in relativistic electrodynamics both classical and quantum. V for voltage difference in circuit analysis (yes we do that too).
Math is like that. It is abstract so it doesn't really matter what the words symbolize. It is necessary however that the formula is consistent in theory and experiment.
Upvoted before watching
Fantastic explanation! Bravo!
Thanks
Another important point, and a common misconception, is that using two meters to measure voltage and current in an AC circuit does not necessarily give you the load power. That can only be achieved with a wattmeter. It makes no difference if the meters are 'True RMS' or not, either. They still do not give 'True RMS' power where the load is inductive or capacitive.
I suspect that many of the claims for 'Bedini motors' and the like of over-unity energy are down to not understanding AC power measurement. They typically use some kind of interruptor to create a pulsating current in a stator coil which rotates magnets, and then use either the same coil or a second coil output, rectified, to charge a battery. Under these conditions it is surprisingly difficult to accurately measure power in and power out, which probably leads to a lot of 'red herring' results.
Well done Dave! Best explanation ever!
I think there is an error starting at around 12:38 where Dave reduces the voltage to 3V, 2V, then 1V to show the decrease in energy dissipation. At ~12:45 he switches the Metrahit display back to the power reading and it continues to show 5W. I think the system is drawing a constant 1A so this should show as 3W, 2W, then 1W. Perhaps he should have reset the meter.
And it once said "An electronics engineering video blog for anyone INVOLVED in electronics design" ..
Actually a super useful video. Thanks for making this!
Careful with confusing expressions like "power over time", as "x over y" in maths means x/y, not x*y. Also, at 8:01 and 9:41 you say "Energy is power per (unit of) time". "Per" also denotes division, which is not correct here. So instead of saying "200W per day", it should be "200W for a day", because "for" indicates multiplication. Correctly used for example at 10:14.
10:31 "One is instantaneous and one is a measurement over time" Does not compute. Define instantaneous. instantaneous is a measurement of time
The Dam is always my go to for this.. as it is more relatable to most people.
Excellent tutorial. Expecting more of these tutorials soon.😊
if I understood correctly. It's better to express energy in A/h when we are talking about constant systems where the source of voltage is the same over a period of time ?
Near the beginning, when talking about static electricity, the reason there is not much energy despite there being 10s of kV, is because _there is very little charge_.
Thank you. also, thank you too.
I did notice that contradiction at the being, meaning some math was wrongly done.
Dave once again you're the man!
Nicely explained
Working back from energy is probably the easiest approach.
Energy: 1 J = 1 W.s (and 1 kWh is 3.6 million W.s, or 3.6 MJ)
Power: 1 W = 1 J/s (establishes that power is energy per unit time)
Voltage (and current): 1 V x 1 A = 1 W (establishes that you can't calculate power or energy just from voltage, or current, alone).
Dave,
I think there is a serious error at 7:57 when you state "...you are charged for kWh --OVER TIME-- " This would suggest you are paying for --POWER-- (not energy)!
Under your "ENERGY" column you state 'correctly that "E = POWER x TIME', BUT directly following that, you state INCORRECTLY, that: "ENERGY = POWER --OVER-- TIME...this would imply that Joules=Watts/Second!!!
The service we get should really be called the "ENERGY COMPANY" not the "Power Company"....or am I not seeing something correctly...a certain possibility!
Thats weird, the timer in your Metrahit DMM doesn't appear to count the seconds properly. It appeared to lag by half a second on one count, then overcompensated by counting the next second within half of a second. Or perhaps thats some sort of visual artifact from your cameras shutter-speed?
Great video as always, Dave.
Nicely done. Now explain the difference between accuracy and resolution for the new players following along.
Dave, could you explain constant current and constant voltage led drivers?
Subscribed, Thumbs up, and Thank you.
That was great, a few well more than a few are getting confused on power, voltage has nothing to do with power/current in this instance the people that think this are trying to use engineering equations in there head to see voltage moving when thats not what he is explaining.
1. The water is POTENTIAL ENERGY it has the potential to do work
2. Generator, which is in the DAM = VOLTAGE
3. And the flow of water which has potential to do work generates POWER
Stop trying to use Voltage as a moving object, when thats not what he is trying to explain.
It is allways nice to remember the basics, and to teach them to people... I guess you could try to explain the power, instead of watts / s, as the time you need to transfer 1 joule, that way, you could say that is independent from the time, since it would be the one defining the power... but it is easier to people to understand watts rather than mili/micro seconds i guess...
WOW thanks, now I've got it!
So the reason that high voltage with wary low current don't kill is that even when the voltage are i.e. 20.000V you are only getting "drops" on your head.
While lower voltage with height current is like getting a bathtub of water from i.e. 2 meter above your head and it can therefor easily throw you to the ground.
Am I right?
Could you please repeat that bit after "lets get to it"
You skipped a bit about capacity, especially with the dam example.
The dam contains the water so that is its capacity or mAh in battery terms
Energy is the amount of power released over time as you said.
But if its not flowing, no power generated, then there is no energy generated too. But its capacity is still there..
Power is energy in motion
I always explain it to average people like this:
Power is the number of gallons of fuel a car can consume per mile and energy is how much fuel stored in the tank or how much fuel consumed during a trip at a particular M/Gal rate.
Dave, can you tell me what defines how much a power source, (a battery charger for instance) is capable of supplying power?
I see Energy as a stored value.
Power is the flow of the Energy.
Voltage is the potential of that Energy.
Current is the flow rate of that Energy.
Thank you.
Can you do video on whether it's voltage or current that kills.
What I've never been clear on is the relation between charge (Q) and potential difference (V). If you have two identical spheres, and one has more electrons (charge) than the other, I assume this means there's a potential difference (V) between them. Is 1V the potential difference of 1 Coulomb of charge separated by 1 meter, or something like that? I can't find anything that defines a volt that way.
If you measured a battery using constant current at 1 amp the meter would tell you a higher capacity than if you measured at 2 amps due to ESR, right?