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Himanshu posted an Question
April 15, 2020 • 06:56 am 30 points
  • IIT JAM
  • Physics (PH)

Entropy numerical

in this numerical everything is ok but the formula using here is possible only at constant V which is not given then how i predict to use

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    Ruby negi

    Cv is given in the question so there is no other formula to calculate dQ Instead dQ=CvdT.. so don't worry free to apply formulas, don't over think.... best regards.

    eduncle-logo-app

    I m taking about this question only...

  • comment-profile-img>
    Shanu arora

    Answer: it's given Cv in question that's why we are using dQ=Cv*dT . If instead of Cv ,Cp might have given then also the formula remain same for dQ=Cp*dT , it comes from the definition of heat capacity.

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    Abhishek singh Best Answer

    Still have doubts? I will give you an example to fix this concept permanent. Assume your working substance (or partical under study) is water(H2O). Volume of Water at low temperature (i.e. volume of ice) remains fix(as it is solid). Even at transition from solid to liquid, the volume remains almost constant. But on the other hand, water at high temperatures (say, 100°C) change to vapour. There may be a drastic change in volume depending on the size of room. hence at high temperatures, you cannot make the assumption of constant volume. This will help you. Best.

  • comment-profile-img>
    Abhishek singh best-answer

    okay! look, here in the first line, they have written (Aluminium at low temperature) . At low temperature volume is assumed to be fix. it's healthy for you, if you do make a note of this. Remember this (word ) ideas, they will help you in exams. This concept is always true! Best regards.

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