physics question help please
hi, please could I have some help with question 3d of this paper https://www.physicsandmathstutor.com/pdf-pages/?pdf=https%3A%2F%2Fpmt.physicsandmathstutor.com%2Fdownload%2FPhysics%2FA-level%2FPast-Papers%2FCAIE%2FPaper-4%2FQP%2FNovember%202021%20(v1)%20QP.pdf
I've watched videos and apparently the temperature remains constant but I'm not sure why this is the case?
Thanks!
I've watched videos and apparently the temperature remains constant but I'm not sure why this is the case?
Thanks!
Reply 1
12
Original post
by anonymous56754hi, please could I have some help with question 3d of this paper https://www.physicsandmathstutor.com/pdf-pages/?pdf=https%3A%2F%2Fpmt.physicsandmathstutor.com%2Fdownload%2FPhysics%2FA-level%2FPast-Papers%2FCAIE%2FPaper-4%2FQP%2FNovember%202021%20(v1)%20QP.pdf
I've watched videos and apparently the temperature remains constant but I'm not sure why this is the case?
Thanks!
I've watched videos and apparently the temperature remains constant but I'm not sure why this is the case?
Thanks!
the gas can expand and so does work
the heat supplied Q goes into doing work W and there is no change in internal energy so the temperature does not change (an isothermal expansion)
The specific heat capacity of the gas is a material property independent of temperature so will not change
Reply 2
Original post
by anonymous56754hi, please could I have some help with question 3d of this paper https://www.physicsandmathstutor.com/pdf-pages/?pdf=https%3A%2F%2Fpmt.physicsandmathstutor.com%2Fdownload%2FPhysics%2FA-level%2FPast-Papers%2FCAIE%2FPaper-4%2FQP%2FNovember%202021%20(v1)%20QP.pdf
I've watched videos and apparently the temperature remains constant but I'm not sure why this is the case?
Thanks!
I've watched videos and apparently the temperature remains constant but I'm not sure why this is the case?
Thanks!
Can you show the video link?
Either the video is wrong, or you misinterpret the answer, which causes confusion.
Reply 3
13
Original post
by EimmanuelCan you show the video link?
Either the video is wrong, or you misinterpret the answer, which causes confusion.
Either the video is wrong, or you misinterpret the answer, which causes confusion.
https://www.youtube.com/watch?v=v1g35STM86o at 46 minutes
Reply 4
13
Original post
by Drummythe gas can expand and so does work
the heat supplied Q goes into doing work W and there is no change in internal energy so the temperature does not change (an isothermal expansion)
The specific heat capacity of the gas is a material property independent of temperature so will not change
the heat supplied Q goes into doing work W and there is no change in internal energy so the temperature does not change (an isothermal expansion)
The specific heat capacity of the gas is a material property independent of temperature so will not change
But how do you know all of Q goes into doing work? There may still be a smaller increase in internal energy right?
Reply 5
Original post
by anonymous56754hi, please could I have some help with question 3d of this paper https://www.physicsandmathstutor.com/pdf-pages/?pdf=https%3A%2F%2Fpmt.physicsandmathstutor.com%2Fdownload%2FPhysics%2FA-level%2FPast-Papers%2FCAIE%2FPaper-4%2FQP%2FNovember%202021%20(v1)%20QP.pdf
I've watched videos and apparently the temperature remains constant but I'm not sure why this is the case?
Thanks!
I've watched videos and apparently the temperature remains constant but I'm not sure why this is the case?
Thanks!
Original post
by anonymous56754https://www.youtube.com/watch?v=v1g35STM86o at 46 minutes
You have either misheard or misunderstood what the tutor said for this part of the question.
Watch this page at 49:33.
The tutor mentioned the same increases in temperatures before 49:33 NOT the same temperature, which means ΔT is the same.
The gas in this part of the question does not undergo isothermal expansion but undergoes an expansion where the increase in internal energy is the same as previous part of the question.
Reply 6
13
Original post
by EimmanuelYou have either misheard or misunderstood what the tutor said for this part of the question.
Watch this page at 49:33.
The tutor mentioned the same increases in temperatures before 49:33 NOT the same temperature, which means ΔT is the same.
The gas in this part of the question does not undergo isothermal expansion but undergoes an expansion where the increase in internal energy is the same as previous part of the question.
Watch this page at 49:33.
The tutor mentioned the same increases in temperatures before 49:33 NOT the same temperature, which means ΔT is the same.
The gas in this part of the question does not undergo isothermal expansion but undergoes an expansion where the increase in internal energy is the same as previous part of the question.
how do we know that increase in internal energy is the same?
Reply 7
Original post
by anonymous56754how do we know that increase in internal energy is the same?
The change in internal energy depends on the temperature change ΔT, as shown in the previous part of the question.
As the temperature change ΔT is the same, the change in internal energy should be the same.
Reply 8
13
Original post
by EimmanuelThe change in internal energy depends on the temperature change ΔT, as shown in the previous part of the question.
As the temperature change ΔT is the same, the change in internal energy should be the same.
As the temperature change ΔT is the same, the change in internal energy should be the same.
but how do you know the change in temperature is the same?
Reply 9
Original post
by anonymous56754but how do you know the change in temperature is the same?
Command word such as suggest, IMO is the most difficult question to answer.
In CAIE, suggest means “apply knowledge and understanding to situations where there are a range of valid responses in order to make proposals”.
This is the tricky part for this question where you need to make the judgment.
To compare 2 experiments, something always remains unchanged in both sets of experiments.
In writing the First law of thermodynamics for the second experiment, where the pressure is constant.
ΔU = Q + W
ΔU = Nm c_p ΔT − pΔV --- (1)
where c_p is the specific heat capacity which we need to “determine”.
While the First law of thermodynamics for the first experiment in c(ii) is
ΔU = Nm c_V ΔT --- (2)
where c_V is the specific heat capacity which we have found in c(ii).
By comparing (1) and (2), the only possible assumption or proposal is that the increase in internal energy is the same in order for us to make a valid comparison between c_p and c_V, or else there are would be too many variables and there is no way for us to make comparison.
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