Thermodynamics - A Level Physics
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- Опубліковано 12 вер 2024
- Continuing the A Level Physics revision series with Thermodynamics and Thermal Physics - covering Boyle's, Charles' and the Pressure Laws, the 4 laws of Thermodynamics and Specific Heat
What I love about your channel is that the videos do not overly-simplify the mathematics used to derive the equations. In today's A-Level Physics syllabus, there are hardly any rigorous derivations due to the fact that they have completely removed all of calculus. At least we can get a feel of what physics really is like with your videos. Thanks a ton!
exactly!!
Thanks. I hope you find my A level series helpful. All good wishes for the A level exams.
Any more videos in the making?
What is efficiency of aneroid barometer in joules ?
@FelipeZucchetti Thanks for watching. Your flame is a source of heat. Its temperature is much higher than that of the gas thermometer (or heat wouldn't flow from the flame to the thermometer (2nd Law of Thermodynamics). It is likely that the flame is delivering a constant rate of heat so you would expect to see the temperature rising uniformly with time.
sir can I ask for your help for some mind-bending physics problems....
Specific heat remains near constant over a wide range of temperatures but varies at lower temps. I am no expert on the reasons but you could look up the Einstein-Debye effect for more information. In essence the quantum effects have a greater effect.
@DrPhysicsA, I wish you were teaching me physics right now. The way you put things and the way you speak, speaks to me and it feels so much easier to grasp. I'm failing Physics right now and I spend the majority of my time studying physics than any other class. Thank you for this channel.
I am too at 109375375
I just finished my O level physics, I'm hoping my confusion as I watch this is normal.. However, I find this fascinating and fires enthusiasm in me to start my AS physics next school year.
I remember doing this in A Level, & I think also GCSE (about 25 years ago); the part about specific heat for melting and boiling was jointly termed Latent Heat.
Nmv^2/3 = nRT
Multiply both sides by 3/N
mv^2 = 3nRT/N
Divide both sides by 2
mv^2/2 = 3nRT/2N
@FelipeZucchetti But the concept of specific heat does not require heat to be supplied at a steady rate. It simply says that to raise the temperature of 1 kg of water by 1 degree you need to supply 4180 Joules of energy. You could do that by placing it next to a hotter body such that as the water warmed up the hotter body cooled down. In those circumstances the heat exchange might not be at a constant rate.
Yes you are right and that was what I was trying to say. If it take x amount of heat to raise 1kg of water by 1K, then it will take approx 500x that amount of heat to take 1kg of water at 373K and convert it to steam at 373K
The volume would become zero at absolute zero. But you can't get to absolute zero. Pressure would also become zero, meaning that the atoms/molecules were effectively stationary with no kinetic energy.
A levels are the exams taken in the UK (and elsewhere) by students usually aged 17-18 ie just before they go on to university.
Sir,I'll be sitting for the A'Level Exams in less than 4 months and for someone who doesn't grasp physics well,your videos are priceless..Thank you so much :)
Damn do u remember this comment?
@@Darkclownexists do u
@@shomik99 kinda but damnn been 7 months already
@@Darkclownexists damn D:
You might want to look at my video on Entropy. Thermodynamic stability occurs when a system is in its lowest energy state, or chemical equilibrium with its environment. So you need to establish what determined whether or not something is stable. I think chemists look at Gibbs Free Energy as a key factor (see Wikipedia). My video does not go as far as Gibbs energy, but it does derive the concept of entropy which is an important factor. G = H - TS, and my video defines both H and S (T is temp).
Great video thank you! Super helpful, your style of work is also amazing, even the old camera quality can't hide it
Very helpful video! The only thing is that the new sign convention is actually dQ=dU+W i.e if work is done on a gas to increase the internal energy then the thermal energy change will be positive. Just thought I'd point this out because I don't know about other exam boards, but AQA certainly follows the new sign convention
I agree. Different people use different sign conventions. The key thing is to be consistent.
what are u talking about girl i mean hot girls are always dummmm
talk 2 me
You can't do the calculation based on the time you observe the particle. dp/dt is the total rate of change of momentum based on all the molecules in the gas. That will be determined by how often each of the finite number of particles hit one of the surfaces. No reason for that to blow up.
Just a small point. It`s not, "degrees Kelvin", just Kelvin. Your vids are very good.
Thanks for sharing memories about Michael Henry Flanders and his partner Donald Swann and their contribution to thermodynamics 🙂
Absolutely amazing explanation !!
Thanks this makes specific heat and kinetic theory much clearer, but I still have trouble when answering specific heat problems in exam papers, could you do a video where you would show how to tackle some exam questions please ?
Great video, thanks for all the help you have given out to everyone. I am much more fascinated in Physics because of you and your videos :)
it will be nice if you could do a worked example at the end of your videos :)
This is the clearest and most illuminating lecture on the topic I have ever heard. Now, can a volume really be zero ? what really happens at absolute zero ?
Paul G The third law of thermodynamics is that you can never reach absolute zero as explained in this great video
Thank you for your sharing and it helps me a lot. :)
Another thing is that this video shows me concepts in a clear way.
It's easy for me to understand what's happening with thermodynamics.
Sorry to be a chemistry stickler, but hydrogen gas is diatomic. Its molecular weight is c. 2.02 amu.
Of course, you're absolutely right.
Would you ever consider working through Past Paper questions in some videos? It seems like you're working from the OCR A specification mostly and it would be a great resource for revision.
Another great video by the way
I enjoy your videos tremendously. However, I am pausing this one to ask a question. Are you certain of your RMS formula? I may be remembering it incorrectly.
Thank you so much sir! I always found it difficult with thermodynamics.
Firstly Kelvin is not measured in degrees, although the magnitude of one K is equal to 1 Deg Celsius. The word "centigrade" is deprecated by the National Physical Laboratory, as it means something other than temperature.
I loved your lecture. Thank you for sharing this.
At 3:28 you say that (PV/T)=C. What is the though process in order to get this mathematical expression from the graphs. Thank you for your time and patience
You can show that P is proportional to T and that V is proportional to T and that P is proportional to 1/V.
The formula is Q/t = kA deltaT/d
I can hear Bruce Forsyth in your voice occasionally
This is actually not a comment but rather a query. Have you iin any of your very lucidly presented series. dealt with standing waves with respect to sound? I have been trying for quite some time to design and make a mini saxophone but all my attempts have failed as i do not know the formjula which will give me the positions of the tone holes even aproximately. Random attempts at locating tone holes is an endless affair leading to no positive end and terrible wastte of effort k, time and material. I shall be sincerely and very greatly thankful to you if you could inform me of any such formula. I have read that the saxophone is taken to be a stopped conical pipe resonator but acts like an double ended open cylinderical pipe and the formujlar for this type of resonator is what is to be used for the sax tube. But though this formula gives almost accurate results whe applied ot the design of a clarinet which i have made in quantitly, it results in total absurdity when applied to the saxophone body tube. Thank you Sir.
Most sincerely, vivian Astridge
I love your youtube channel, but could you put closed captions on your lectures? Is it diffcult to do it?
8:24 is this true? i thought that we do not note a maximum particle speed in a gas for any given temperature as there is a chance that one particle may be much faster than the average (i.e. it is impossible to have a value of the maximum particle speed)
1000x thanks!
Something that has always bothered me:
11:58 - when calculating the dt part of dp/dt, why does the equation not blow up? It seems like it would, because at 4:55 you state that forces act instantaneously in an ideal gas. For instance, if I only started paying attention to the particle when it was already very close to the wall (say, a distance of .001L), and say I stopped paying attention to it after it rebounds .001L from the wall, then dp = 2mv, but dt = .002L/v and this limit would go to inf.
Boyle's law can be used to show that pV=constant
But then Charles' law and the Gay-Lussac laws can be used alone to show that pV/T=constant, without using Boyle's law at all?
Could you please help me with combining the laws? Thanks!
I enjoy your videos a lot, so thanks for sharing with us! They are practical and understandable.. I hope you can make a video about statistical thermodynamics. it's a subject still something difficult to unserstand. thanks
Hi DrPhysicsA, look at the equation of KE per molecule is directly proportional to absolute temperature. I thought this formula is applicable to idea gas only? I have not encounter any theory that shows the same formula is applicable non ideal gas such as a solid.
In 13:25 , I can`t see how we get that N/3 is the total number of molecules.. Help.
We are saying that there are N molecules moving in all directions. But if we resolve those movements into the X, Y, and Z directions we effectively have N/3 molecules moving in each direction.
Ahhhh, ok2x sir. I see now. Thanks :)
DrPhysicsA 13:21 If you are considering the Force due to pressure on one of six surfaces of a cube, then it seems to me that the N/3 term should really be N/6.
--thanks for publishing these videos
Anthony Phillips
Because there are 6 planes in a cube, there are 3 ways to move. If a particle bounces off the left side of the box, it moves along one of the axes, thus you can resolve that 1/3 of the particles in the box bounce off both the left side and the side opposite to it, since particles bouncing off either the left or right side move along the same axis.
Basically, if a particle is moving along the x-axis it will bounce off both the left AND the right side of the box. For 6 sides to bounce of, there are 3 directions to move along :) Hope I made something clear.
+DrPhysicsA sir, so N/3 mean we only consider force in one direction?
Perfect as usual! Subscribed.
isnt 276.16 k near one degree?
Please show efficiency of aneroid barometer in joules ?
If we made a bigger barometer then will it turned the turbine ?
thermal equilibrium doesn't mean that there is no heat flow. it means heat flows from one body to another and vice versa at the same rate
Thanks, these videos are excellent for quick revision :)
Very comprehensive, thanks.
If an adiabatic change will occur if the work is done very fast so no heat transfer has time to take place, then if the work is done very slowly will the change be isothermal? Since there is too much time for internal energy to build up in the system because heat transfer will always take it away to keep it in thermal equilibrium with the surroundings.
I think there is an error or misleading statement at the end. Surely you meant to say that it would take 500 times as much energy as the SH to turn the whole kg (litre) of water into steam. Just reaching 373 K would begin the boiling process and start turning small quantities of the water into steam ("the jug is boiling"), but boiling away the whole litre into steam takes much longer for this reason. Which is good, otherwise, making one's tea would be a quite fraught process.
Wikipedia States Absolute Zero "The zero point of any thermodynamic temperature scale, such as Kelvin or Rankine scale, is set at absolute zero. By international agreement, absolute zero is defined as 0K on the Kelvin scale and as −273.15° on the Celsius scale.This equates to −459.67° on the Fahrenheit scale and 0 R on the Rankine scale.Scientists have achieved temperatures extremely close to absolute zero, where matter exhibits quantum effects such as superconductivity and superfluidity."
This video is old so don’t expect reply, but is everything here still relevant for the new a levels?
Hi, very helpful videos!
quick question on the 3rd curve of explaining the different systems (constant pressure). as you have showed in the beginning of the video that pressure and Temp are directly proportional, so when you decrease the temperature wouldn't it imply that you decreasing the pressure as well?
Thanks
PV = NkT, so this means that with a decrease in temperature, if the volume decreases pressure stays constant.
I'm not Einstein but that Carnot cycle is screaming 'stream engine' at me. I can imagine the pistons going in and out, pistons affecting volume and pressure. A bit more on this to get an intuitive picture in this application would have been good.
this is so awesome. I'm revising chemistry at the same time!
What about zero point energy given by QM, which can be backed up by the heisenberg uncertainty relation between the conjugate variables of energy and time?
Wouldn't the force be the change in momentum divided by the time it makes contact with the box wall. The model is weird because it suggests that there is a force changing its momentum throughout the whole journey 2L. can you please explain this?
you r an physics rockstar
sir
what exam board is this for? would it be alright for CCEA?
sir can u make on why specific heat of vapouring is higher than specific heat of fussion
Another great vid!
Assuming (1) the universe is spatially infinite, and (2) there are no voids large enough as such that matter exists isolated from starlight 13.72 billion light years in any direction, then would there be no truly thermodynamically closed systems?
How does specific heat vary with temperature starting from absolute zero?
+drphysicsA
Isoterms have more energy due to their constant temperature or continuous heat in... so its curve is gentle and lie above adiabatic....
ahhhh.. it is compression.. so heat was leaving system for isotherm...
I think I’m the only one of my friends that finds these sorts of thing so fascinating. It’s incredible. I’m very fortunate to live in a time where I can binge watch someone execute quantum mechanics whenever I want. Thanks for the videos and sharing your wealth of knowledge.
first question to F = dp/dt. As we know this means the change of momentum during the time dt, or the rate of change of mom. during the time of THAT change. According to your (the classic derivation) the dP changes during the total fly time inside the L which is NOT true. You can only use this time 2L/v if you assume ALL the 1/3N of molecues umklap the momentum. You can NOT use this time for one particle as you did.
i'm not understanding why dp/dt = 2mv^2/2L
Sorry for the late reply i did look at the other video and it was a great help thank you very much and sorry again for the long time in reply :-)
p.s Got an A in the assignment :)
perfect explanation.
So what's the difference between Adiabatic and Isothermal? is it that in Adiabatic the temperature is allowed to increase but not from an external source?
Adiabatic - there is no heat transfer in or out of the system - it is insulated. Isothermal - there is no change in temperature - the entire system is placed in a heat bath of constant temperature. So yes, in an adiabatic system the temp can increase but not from heat coming in from the outside.
DrPhysicsA When will u next upload a video?
U have been inactive for 3 years..
I didn't realise A-Level Physics was as complex as this.
I failed GCE Science from school with an F Grade.
Actually, this seems quite easy.
sir what do you mean by a level physics,,, tnx,,, it help a lot..
I feel like there are certain conditions that are abused by this classical model that aren't fully explained. When counting the number of molecules that are in the system we assume that all the molecules can only move in 3 axis, i feel like that is a big assumption at 10:00.
+justin joy I know I'm 8 months late and you've most likely already done the exam, but just to explain the velocity thing; the particles can only move in the x, y, and z plane, and therefore their velocities would be given as a vector of x, y, or z. Say the particle is moving at a horizontal angle to the x plane, its velocity would simply be (x)cos(a) or (y)cos(90-a).
Sorry i has a very stupid question. Can you help me ?
Like you said the amount of E required to change ice to water is 80x E to raise the Temperature. So how you can melt the ice without changing it's temperature. ?
+Cong Xuan When you heat water, you add energy which gives kinetic energy to the molecules which amounts to higher temperature. When you melt ice the energy goes principally into breaking the solid state bonds rather than giving KE.
DrPhysicsA I understand, ty
relevant and helpful indeed
pls sir, I would like you to help me with the following problem; determine the quantity of heat conducted in thirty minutes through an iron plate 2.0cm thick and 0.01m2 in area the temperatures if the two sides are 0 degree Celsius and 20 degree Celsius. the coefficient of thermal conductivity of iron is 50.4 J/smC .
can you do a video on bose-einstein statistics
Who mentioned reflection:?
Sir, please help me solve the following question
During a thermodynamic process the pressure of a diatomic gas is proportional to volume raised to the power -4( negative of 4). Find the specific heat of gas during this process. (The answer is 13R/6)
Manneet Kaur Use the characteristic equation of an Adiabatic process
Legend!!!
Thankyou
Interesting stuff.
I wish i didnt have to go to school and learn physics, i'ld rather give my paper after watching these videos and doing some past papers.
How is the change in momentum 2mv? Can you please elaborate more on that?
In the simple example we are considering, the particle travelling to the right (say) hits the side of the container with momentum mv in the right hand direction. When it rebounds it is now travelling to the left at mv. The change in momentum is mv - -mv = 2mv
+DrPhysicsA i had the same question but thanks it makes sense now
DrPhysicsA
Hello, in the A2 level book that i have the change in momentum is given as follows:
-mv-mv=-2mv
Is that still correct and what is the diffrence if yes?
Thanks in advance.
Thank you so much
Been given an assignment to doa 5 slide presentation of thermodynamically stable ive just started a-level chemistry and never heard of this ... SOS
Also my techer is probably reading this =C
professor do you please learn us quantum mechanics problems HRK chapter no. 48
Sorry, but 1 mol, (not mole). of hydrogen gas, has a gram molecular wt. of 2g. Under normal conditions pairs of hydrogen atoms make up the gas, and 6.03^23 hydrogen molecules have a mas of 2g.
very helpful
Negative temperature is imaginary???like iota???but we see it's possible???how ???
My lord , i am really very happy that i became yur student ,the lecture was wonderful and concepts explained clearly.
Let's be honest, we all looked up the "heat is work and work is heat" song
I did
0:45 in my book this graph is a straight line through origin pls help which one is correct
Mohammad Daniyal I think it is correct in your book. As P=nRT/V the y-intercept of the line shoud be equal to zero (compare the equation to the equation of a line y=mx+c; where c is the y-intercept). And as this equation can also be written as 1/V=P/nRT the x-intercept should also be equal to zero (x=my+c where c is x-intercept). Thus the line should pass through the origin.
Nischay K makes sense thanks
In this video, professor explain in term of degree celcius, in kelvin i.e: you meassure P-T at 0,0 it means at 0 K you have 0 pressure, but u can't go there because it's impossible (at least what i know) to reach absolute zero, hope you keep enjoying physics
Are topics in Phys.
of course dick head
Really good but I am afraid your voice reminds me so much of Brick Top from Snatch. Not a bad thing at all but I just kept thinking your start talking about pig farms😂. Really good though
i want it for 4
months
It isn't degrees kelvin, it's just kelvin. This is because kelvin isn't a degree system, it's absolute. There are no negative kelvins.
Najey Rifai aap parha lo
Ali Moazzam Pardon?
I thought you were urdu speaking. That means "why don't you start teaching if you know so much?" :P
Ali Moazzam I'm not urdu, and I may know a lot, but I'm shit at teaching!
chill. i was being sarcastic anyway xD
My mind is going explosion
crazy