I don't know if I have gotten this all wrong, but isn't the sign convention explained here wrong? 1) Work done by the system- (-w) 2) Work done on the system (+w) This is what I have learned. Please correct me if I'm wrong. Edit- So this tutorial was for physics, not chemistry. Anyways, it's more interesting to discover that we use different sign conventions in physics.
I am looking for a validation of my understanding of the work done on the system because I feel like what is in the video is wrong, and I found this comment hahahaha. I searched for the work done on the system in physics and, similarly in chemistry, they are positive. So the video is indeed wrong.
@@markvillacampa4314 The video isn't wrong. He has changed the signs in the equations too. So the equations will always work. It's just a different perspective to look at.
Amazing video! But please specify that this is from physics' point of view. according to chemistry the signs are different. This kind of induces confusion. THANK YOU!
@@na-chan163 it's positive in phyics because we are describing the system's actions on it's surroundings, and it's negative in chemistry because the system is "throwing" out work (idk if im completely correct but im sure this is a good way to think of it)
Awesome visual examples and simplified to absorb the information being released, making understanding and keeping it in so much easier. Thank you, Prof. Dave!
expansion of the gas W < 0 and compression of the gas W > 0. Because in the first case, the system does work on the surroundings so it loses work while in the second case, the surroundings does work on the system so the latter gains works which will be positive
Thanks for the video, but am confusing a bit . If work done by the system that mean system loss energy to surroundings which decreases the internal energy of the system , so it should be negative. Please need more explanation
Professor Dave: could u do YT thermodynamics videos with examples of processes from IC engine, jet engines, rockets, compressors, gas turbines, steam turbines, boilers, refrigeration cycle, heat pumps. Thermodynamics concepts would stick to comprehension and memory by using heat engines as examples. This video was fantastic and not easy to forget now because u used mechanical examples. Thank u so much
@@Ice-yp4wg wdym? Specific internal energy? Sometimes questions want u to find out the internal energy of the system before it went under compression or expansion process
@@Ice-yp4wg no idea. But I guess it's because it's a good letter to use since other letters are used to define other properties such as temperature, pressure or enthalpy
Hey quick question for those interested. How much do you need to cool a solar cell operating at, let's say, 23% efficiency? My thoughts are that a solar cell should not change its internal energt U, so in other words deltaU or dU/dt should be 0. So 23% of the solar energy becomes electrical work, while the rest of the sun's power (1-0.23=0.77) is transferred as heat that, without cooling, would accumulate in the solar cell. In order for dU/dt (delta U) of the solar cell to be 0 you need to fulfill Q=W, so in other words you need to cool the cell to such an extent that the only heat that isn't cooled off equals the electrical power of the solar cell, in this case 0.54 times the power of the sun? Is this way of thinking correct? I would very much appreciate any input.
Yes, indeed, that is correct. This is why the panels heat up, if you turn off the system and make them remain at open circuit. The lack of a destination for the power to go, means that they heat up to a temperature where they can radiate more energy to the background. This is counterintuitive, because most of the time, operating electrical equipment makes it heat up, rather than cool down.
Engineers and Chemists view work differently. As he explains, Work is positive if the contained volume does Work against the atmosphere, like the expansion of a gas in a piston assembly. Chemists view Work as positive if the environment does work on the contained volume, such as a compression of the gas.
Please note that you have incorrectly applied the signs for work. Work is (-) when it is done by the system on the surroundings. Work is (+) when it is done on the system.
the difference between changes in enthalpy and internal energy for the explosion of trinitrotoluene, TNT, at 25°C producing carbon dioxide, nitrogen dioxide gas and water vapor will be in what Joules?
Hello Professor Dave, please make me understand how is the work done by the system positive? When heat is applied then gases expand against the downward force of the piston, so product of force and negative displacement is a negative work done. Isn’t it? I hope you got what I am trying to say.
@@davidisaacgalang3000 It's nothing more than a sign convention. Different disciplines use different standards for the sign on heat and work, to keep track of them entering and leaving the system. It is just a language you translate back to words, to explain how the energy exchange happens. There is no reason work has to be positive when it is done by the system, other than "because we said so". I'm accustomed to the heat engine sign convention, whereby work done by the system is positive (that's the purpose of an engine), and heat added to the system is positive (that's the source of energy for a heat engine).
you are awesome sir i was unable to understand this topic...again again.... but your way is very simple and very useful to me.... keep on sir...that has a positive effect on us...😀
I have a confusion question, please. In checking comprehesion question, if the system absorb heat Q = 60 J for this to occur, how could the delta U be negative, since negative delta U would be temperature going down..... how could absorbing Q cause the temperature to go down?
How about when the pressure stays constant and the volume and temperature changes? Like, a gas tube with a movable piston on it. When you give heat to it, the volume and internal energy both increases. dW≠0, dU≠0, dQ≠0. Does this have a special name?
Constant pressure processes are called isobaric processes. Iso means same, and bar refers to the unit bar for pressure and the barometer to measure it. Isobaric = constant pressrue Isothermal = constant temperature Isochoric = constant volume Isentropic = constant entropy (another name for adiabatic reversible processes) Isenthalpic is the kind of adiabatic process that is inherently irreversible, such as expansion through a valve with friction, as happens in the refrigeration cycle.
is there joules of internal energy added to the kinetic energy when a hockey puck is sliding across ice? or is there no internal energy added to kinetic energy?
Amit Kushwaha quite confusing. If work done on the system by the surroundings, therefore its positive. Same goes for work Done on the surrounding into the system. *head hurts* correct me if I'm wrong, thanks.
In Chemistry, we are looking at it from the point of view of the "system" so work done on system is positive since system is gaining internal energy. In Physics, we look at it from the point of view of "surroundings" so work done on system is negative since the surrounding is losing that energy.
U said constant temp. Then delta U=0,but when the state of a substance changes for eg when ice melts then temp remains constant but the internal energy changes dye to change in potential energy. How this happens?
Дмитрий Борисов Дмитрий Борисов 18 секунд назад (изменено) How is it possible that the eqution on Chemestry books is +w and in physics books it is -w. May be Work in physics has (-) in its formula like W= - integral (pdV) ?
my prof. puts links to ur videos and that means 2 things 1. he knows nothing about chemistry which he actually doesn't(don't ask) 2. u r way better than him to the point we watch YT videos in lectures instead of him doing his f job 🙂
Hi dave, are isovolumetric and isochoric the same? Also what is the difference between isothermal and adiabatic processes? Edit: also if there is no heat transfer then the system and surroundings must be in equilibrium, so no work should take place?
يا رجُل ماهذا الشرح الجمييييل ، شرح مُبسط وجميل ♥️♥️♥️♥️👏🏻👏🏻👏🏻
كملتي معه ولا ؟ عندي اختبار بكره.
Why couldn’t you have been my professor in college? You explain everything perfectly!
U should do study
My girl 😂😂
Yes
You study this in college. We study this is in 10th grade in asia💀☠️☠️
@@jefrreyjeffery2192 We study this in college too, we do more than this, but I'm coming back to the basics, Also Asian here.
@@anuragchaudhary6307maybe you two live in two different countries/regions
,after all Asia is a big place
I don't know if I have gotten this all wrong, but isn't the sign convention explained here wrong? 1) Work done by the system- (-w)
2) Work done on the system (+w)
This is what I have learned.
Please correct me if I'm wrong.
Edit- So this tutorial was for physics, not chemistry. Anyways, it's more interesting to discover that we use different sign conventions in physics.
I am looking for a validation of my understanding of the work done on the system because I feel like what is in the video is wrong, and I found this comment hahahaha. I searched for the work done on the system in physics and, similarly in chemistry, they are positive. So the video is indeed wrong.
Yes, video is telling wrong about the sign conventions.
@@markvillacampa4314 The video isn't wrong. He has changed the signs in the equations too. So the equations will always work. It's just a different perspective to look at.
Yes work done on the system is positive, work done by the system is negative
I swear to study thermodynamics eagerly if he's my professor.Deserves a lot of subscribers and likes.
Sometimes hearing the same information from a different person helps very much!
I agree with you.
i want all Teachers as you. You explain a lot of things in few minutes.Thank you..
As always, clear, and most importantly, concise. No wasted words or time. Well done, Professor Dave
3:29 dude you're wrong bro... If work is done on the system, its sign is positive. If work is done by the system, its sign is negative.
Right 👍
its because the sign convention used here is valid for physics but not chemistry and I think he made it from physics point of view.
Amazing video! But please specify that this is from physics' point of view. according to chemistry the signs are different. This kind of induces confusion. THANK YOU!
thank you so much. i thought i was going crazy.
@Mohamed Sherif how is that so?
@@na-chan163 the surrounding energy is the atmosphere's energy and the system's energy is the internal energy
Fatima Isra work done by system (expansion) is negative for chemistry but positive for physics. Can you pls explain this?
@@na-chan163 it's positive in phyics because we are describing the system's actions on it's surroundings, and it's negative in chemistry because the system is "throwing" out work (idk if im completely correct but im sure this is a good way to think of it)
Professor Dave helping me cram for the physics GRE, what a hero
Awesome visual examples and simplified to absorb the information being released, making understanding and keeping it in so much easier. Thank you, Prof. Dave!
I think I'm dropping thermodynamics
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Good one 😂
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We need more professors like you in India ...
Exactly
I wish your channel was bigger
me too, friend!
It is now
Now it's bigger than ever!!!
@@ProfessorDaveExplains that's amazing
and could you explain why U become zero when temeperature is constant plz ?
expansion of the gas W < 0 and compression of the gas W > 0. Because in the first case, the system does work on the surroundings so it loses work while in the second case, the surroundings does work on the system so the latter gains works which will be positive
Thanks for the video, but am confusing a bit . If work done by the system that mean system loss energy to surroundings which decreases the internal energy of the system , so it should be negative. Please need more explanation
I’m obviously not Prof Dave but I think it’s positive because the equation has a negative W, whereas most equations have a positive work (dU = Q + W)
I'm really impressed , the way of teaching, how u remember all those things, can u give me any tips to remember easily
You do an amazing job ♥ !
Professor Dave: could u do YT thermodynamics videos with examples of processes from IC engine, jet engines, rockets, compressors, gas turbines, steam turbines, boilers, refrigeration cycle, heat pumps. Thermodynamics concepts would stick to comprehension and memory by using heat engines
as examples.
This video was fantastic and not easy to forget now because u used mechanical examples.
Thank u so much
I think there are mistake in work subject
Thanks for your brilliant explanation
Thank you for making this video.
Well Explained.
It Helps me a lot.
Question: Why must heat be represented by "Q" and internal energy is to be represented by "Delta U"?
delta U means the overall change in internal energy. delta U= U2 - U1
@@heinzguderian9572 but why use U specifically?
@@Ice-yp4wg wdym? Specific internal energy? Sometimes questions want u to find out the internal energy of the system before it went under compression or expansion process
@@heinzguderian9572 The letter U I mean
@@Ice-yp4wg no idea. But I guess it's because it's a good letter to use since other letters are used to define other properties such as temperature, pressure or enthalpy
Thank you so much for sharing this 🙏...Such a clear concept.
please make a video on carnot engine or carnot cycle
that would be the second law, the one right after this!
are in chemistry the concept of sign of W is reverse in physics
Sir you have done wrong here about sign convention work done by the system is negative and work done on the system is positive
That's chemistry. This is a physics tutorial.
@@ProfessorDaveExplains okh sir my mistake actually I am in 11th class and a neet aspirant so I don't know it well and thankyou for replying
Hey quick question for those interested. How much do you need to cool a solar cell operating at, let's say, 23% efficiency?
My thoughts are that a solar cell should not change its internal energt U, so in other words deltaU or dU/dt should be 0. So 23% of the solar energy becomes electrical work, while the rest of the sun's power (1-0.23=0.77) is transferred as heat that, without cooling, would accumulate in the solar cell.
In order for dU/dt (delta U) of the solar cell to be 0 you need to fulfill Q=W, so in other words you need to cool the cell to such an extent that the only heat that isn't cooled off equals the electrical power of the solar cell, in this case 0.54 times the power of the sun?
Is this way of thinking correct? I would very much appreciate any input.
Yes, indeed, that is correct. This is why the panels heat up, if you turn off the system and make them remain at open circuit. The lack of a destination for the power to go, means that they heat up to a temperature where they can radiate more energy to the background. This is counterintuitive, because most of the time, operating electrical equipment makes it heat up, rather than cool down.
Why does my textbook say deltaU= Q + W ?
333 Studios cuz you are Indian. You consider work done by the system +.
Engineers and Chemists view work differently. As he explains, Work is positive if the contained volume does Work against the atmosphere, like the expansion of a gas in a piston assembly. Chemists view Work as positive if the environment does work on the contained volume, such as a compression of the gas.
Mufakkir Hussain it is in physics but in chemistry this sign is reverse of W
Wrong, because he is studying chemistry, and you are studying physics.
Even my textbook is saying work done on the system positive
Please note that you have incorrectly applied the signs for work. Work is (-) when it is done by the system on the surroundings. Work is (+) when it is done on the system.
No, that's for chemistry. This is a physics tutorial.
I loved this video. so much good information!
3:27
Is it correct?
Work done on the system is +ve
And
Work done by the system is -ve
Correct me ......
If I am wrong
Sir your way of explaining topic in detail is the #best.....
the difference between changes in enthalpy and internal energy for the explosion of trinitrotoluene, TNT, at 25°C producing carbon dioxide, nitrogen dioxide gas and water vapor will be in what Joules?
thank you sir.
Good
0=Q-W when we move Q on the other side of equal sign why don't we change it's sign?
Thank you so much!
THANK YOU PROF!!!!!!!!!!!!!!!!
Thanks a lot sir!
You made it easy
Thankyou Professor
Thinking I've understood and still failing comprehension question😭😂Lord do me Mercy 🤲
Anyone else got exam today GL Guys also Professor Dave u a life savour
short and easy to understand thanks
In Chemistry point of view, is the answer for the first problem equals to -26J?
And the last problem's heat is +40J?
In checking comprehension, why the operation is addition?
Hello Professor Dave, please make me understand how is the work done by the system positive? When heat is applied then gases expand against the downward force of the piston, so product of force and negative displacement is a negative work done. Isn’t it? I hope you got what I am trying to say.
This is exactly why I came to the comment section. Work done BY the system is NEGATIVE and work done ON the system is POSITIVE
@@majinDuu yes, I was really confused too
@@davidisaacgalang3000 It's nothing more than a sign convention. Different disciplines use different standards for the sign on heat and work, to keep track of them entering and leaving the system. It is just a language you translate back to words, to explain how the energy exchange happens. There is no reason work has to be positive when it is done by the system, other than "because we said so".
I'm accustomed to the heat engine sign convention, whereby work done by the system is positive (that's the purpose of an engine), and heat added to the system is positive (that's the source of energy for a heat engine).
Tq very useful
you are awesome sir
i was unable to understand this topic...again again....
but your way is very simple and very useful to me....
keep on sir...that has a positive effect on us...😀
Why the velocity increases from Sonic to super Sonic in diffuser (for steam ) ? It should decrease as the area is increasing
thankyou sir, it is very useful for me
Wow. Thank You
Great video! This helped me a lot!
It is ∆U= Q+W Or ∆U= Q-W ? Both are correct? Both we have to write to explain 1st law of thermodynamics?
Opposite conventions in chemistry vs. physics. This one is a physics tutorial.
Thanks.
I have a confusion question, please. In checking comprehesion question, if the system absorb heat Q = 60 J for this to occur, how could the delta U be negative, since negative delta U would be temperature going down..... how could absorbing Q cause the temperature to go down?
How is the total energy of the universe constant if the universe expands
thank you now i understanding therom esay.
Thank you!
Sir, work done on the system is +ve.
And answer of numerical you solved in vedio is 174 J.
Please respond
video*
Love to hear more from you
Different way of expression ...in some books...it is Del U=q+w....?????
How about when the pressure stays constant and the volume and temperature changes?
Like, a gas tube with a movable piston on it. When you give heat to it, the volume and internal energy both increases. dW≠0, dU≠0, dQ≠0. Does this have a special name?
Constant pressure processes are called isobaric processes. Iso means same, and bar refers to the unit bar for pressure and the barometer to measure it.
Isobaric = constant pressrue
Isothermal = constant temperature
Isochoric = constant volume
Isentropic = constant entropy (another name for adiabatic reversible processes)
Isenthalpic is the kind of adiabatic process that is inherently irreversible, such as expansion through a valve with friction, as happens in the refrigeration cycle.
Everyone wathing this video please do note that the sign convention used here is only valid for physics, it is the opposite for chemistry.
awesome, great job professor .
keep on
Great explanation... Thanks
When work is done by the system W is negative when work is done on the system w is positive
You said the opposite
Chemistry and physics have opposite conventions. This is a physics tutorial.
@@ProfessorDaveExplains ahh so that's why
Thanks dave
very good expression sir!
I really wish I had a physics tutor like this. Unlucky me
is there joules of internal energy added to the kinetic energy when a hockey puck is sliding across ice? or is there no internal energy added to kinetic energy?
u do explain well include examples as u did in this video
Whn work is done on the system. The sign will be positive.
nope, negative!
Amit Kushwaha quite confusing. If work done on the system by the surroundings, therefore its positive. Same goes for work Done on the surrounding into the system. *head hurts* correct me if I'm wrong, thanks.
Work done on system by surrounding should be positive...
In Chemistry, we are looking at it from the point of view of the "system" so work done on system is positive since system is gaining internal energy. In Physics, we look at it from the point of view of "surroundings" so work done on system is negative since the surrounding is losing that energy.
@@Dsc009 so why prof Dave used -w ?!
If in chemisty is +w and we are studying chemistry ?!
Thanks a lot!
you saved me Mr!lots of thanks from Ethiopia
Mr. Dave, you are awesome
What’s meant by ‘energy’ in this context?
U + kinetic energy + potential energy = 0, U- Q + W = 0. So , are kinetic energy = W, and Q = potential energy????
U said constant temp. Then delta U=0,but when the state of a substance changes for eg when ice melts then temp remains constant but the internal energy changes dye to change in potential energy. How this happens?
good explanation sir
Very great video
Awesome tutorial.
Дмитрий Борисов
Дмитрий Борисов
18 секунд назад (изменено)
How is it possible that the eqution on Chemestry books is +w and in physics books it is -w. May be Work in physics has (-) in its formula like W= - integral (pdV) ?
it's just a difference in the convention regarding the sign associated with work done on or by the system
Whew this is a lot to remember
tnx
Nice work
i love your content. pliss don't die❤❤❤
Thanks a lot🌼 Amazing!
thanks
my prof. puts links to ur videos and that means 2 things 1. he knows nothing about chemistry which he actually doesn't(don't ask) 2. u r way better than him to the point we watch YT videos in lectures instead of him doing his f job 🙂
I didn't skip the ad😎😌
Thanks sir
so helpful
thanks much❤❤🌹
Thank you science Jesus
seriously?
Thank yous
Hi dave, are isovolumetric and isochoric the same? Also what is the difference between isothermal and adiabatic processes?
Edit: also if there is no heat transfer then the system and surroundings must be in equilibrium, so no work should take place?
@silverrahul Gotcha, thanks!
Amazing sir
I am from India ❤️
Outstanding