Thermodynamics- AIPMT 2009 Multiple Choice Questions

Here are two multiple choice questions on thermodynamics which appeared in AIPMT 2009 question paper:

(i) In thermodynamic processes which of the following statements is not true?

(1) In an isochoric process pressure remains constant

(2) In an isothermal process the temperature remains constant

(3) In an adiabatic process PV^γ = constant

(4) In an adiabatic process the system is insulated from the surroundings

The only statement which is not true is statement (1). A process in which the pressure remains constant is called isobaric process (and not isochoric process).

[Note that an isochoric process is one in which the volume remains constant].

(ii) The internal energy change in a system that has absorbed 2 Kcals of heat and

done 500 J of work is:

(1) 6400 J

(2) 5400 J

(3) 7900 J

(4) 8900 J

When a quantity Q of heat is supplied to a system it is used to do an amount of work W by the system and to increase the internal energy of the system by ∆U:

Q = ∆U + W

Note that Q given in kilo calories is to be converted into joule which is the SI unit of heat. Therefore Q = 2×1000×4.2 J = 8400 J (remembering that 1 cal = 4.2 J very nearly).

The increase the internal energy, ∆U = Q – W =8400 – 500 = 7900 J.

Find some more multiple choice questions (with solution) in this section here as well as here.

All India Pre-Medical/Pre-Dental Entrance Examination (Preliminary) 2009 (AIPMT 2009) Questions from Thermodynamics

The following questions were included from thermodynamics in the All India Pre-Medical/Pre-Dental 2009 Entrance Examination (Preliminary):

1. The internal energy change in a system that has absorbed 2 Kcals of heat and done 500 J of work is

(1) 6400 J

(2) 5400 J

(3) 7900 J

(4) 8900 J

We have ∆Q = ∆U + ∆W where ∆Q is the heat supplied to the system, ∆U is the increase in internal energy of the system and ∆W is the work done by the system.

Therefore, the increase in internal energy of the system is given by

∆U = ∆Q – ∆W = 2000×4.2 J – 500 J = (8400 – 500) J = 7900 J

[Note that 1 calorie = 4.2 joule, nearly]

2. In thermodynamic process which of the following statements is not true?

(1) In an isochoric process pressure remains constant.

(2) In an isothermal process temperature remains constant.

(3) In an adiabatic process PV^γ = constant.

(4) In an adiabatic process the system is insulated from the surroundings.

Statement (1) is not true since an isochoric process is one in which volume remains constant. So option (1) is the answer.

You will find many useful questions on thermodynamics at physicsplus here and at other locations.

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