Question bank Class 12 Physics Chapter Chapter 4. Thermodynamics

 Question bank Class 12 Physics Chapter Chapter 4. Thermodynamics

Standard:- 12th

Question Bank

Subject:- Physics

Chapter 4. Thermodynamics

MCQ’s ( 1 Mark Each)

1) Which of the following is correct, when the energy is transferred to a system from its

environment?

(a) System gains energy (b) System loses energy

(c) System releases energy (d) system does not exchange energy

Ans: a) System gains energy

2) Which of the following system freely allows exchange of energy and matter with its

environment?

(a) Closed (b) Isolated (c) Open (d) partially closed

Ans: c) Open

3) Two systems at same temperature are said to be in

(a) chemical equilibrium (b) thermal equilibrium

(c) mechanical equilibrium (d) electrical equillibrium

Ans: b) thermal equilibrium

4) For work done to be reversible, the process should be

(a) cyclic (b) isobaric (c) isochoric (d) adiabatic

Ans: d) adiabatic

5) A gas in a closed container is heated with 10 J of energy. Causing the lid of the container to

rise 2 m with 3 N of force. What is the total change in energy of the system?

(a) 10 J (b) 4 J (c) -4 J (d) - 10 J

Ans: b) 4 J

6) The second law of thermodynamics deals with transfer of

(a) work done (b) energy (c) momentum (d) heat

Ans: d) heat

7) Heating a gas in a constant volume container is an example of which process?

(a) isochoric (b) adiabatic (c) isobaric (d) cyclic

Ans: c) isobaric

Very Short Answer (VSA) ( 1 MARK Each )

1) When two objects are said to be in thermal equilibrium?

2) The science of measuring temperatures is called as?

3) State zeroth law of thermodynamics.

4) What is energy associated with the random, disordered motion of the molecules of a system

called as ?

5) A group of objects that can form a unit which may have ability to exchange energy with its

surrounding is called what?

6) On what basis a thermodynamic system can be classified?

7) What is a thermodynamic process?

8) Define heat.

9) What is the internal energy of the system, when the amount of heat Q is added to the system

and the system does not do any work during the process?

10) When does a system lose energy to its surrounding and its internal energy decreases?

11) State first law of thermodynamics.

12) A system releases 100 kJ of heat while 80 kJ of work is done on the system. Calculate the

change in internal energy. (Ans: ΔU = 20 kJ)

Short Answer I (SA1) ( 2 MARKS Each )

1) Draw p-V diagram of reversible process.

2) Draw p-V diagram of irreversible process.

3) Draw p-V diagram showing positive work with varying pressure.

4) Draw p-V diagram showing negative work with varying pressure.

5) Draw p-V diagram showing positive work at constant pressure.

6) 3 mole of a gas at temperature 400 K expands isothermally from initial volume of 4

litre to final volume of 8 litre. Find the work done by the gas. (R = 8.31 J mol-1 K-1)

( Ans: W = 6.919 𝑘𝐽 )

7) An ideal gas of volume 2 L is adiabatically compressed to (1/10)th of its initial volume.

Its initial pressure is 1.01 x 105 Pa, calculate the final pressure. (Given 𝛾= 1.4)

(Ans: 𝑃􀯙 = 25.37 × 10􀬹 𝑃𝑎)

8) Explain the cyclic process.

9) Differentiate between reversible and irreversible process.

10) State the assumptions made for thermodynamic processes.

Short Answer II (SA2) ( 3 MARKS Each )

1) Classify and explain thermodynamic system.

2) Explain given cases related to energy transfer between the system and surrounding –

a. energy transferred (Q) > 0

b. energy transferred (Q) < 0

c. energy transferred (Q) = 0

3) Explain the different ways through which internal energy of the system can be

changed.

4) Write a note on thermodynamic equilibrium.

5) Explain graphically (i) positive work with varying pressure, (ii) negative work with

varying pressure and (iii) positive work at constant pressure.

6) Write a note on free expansion.

7) One gram of water (1 cm3) becomes 1671 cm3 of steam at a pressure of 1 atm. The

latent heat of vaporization at this pressure is 2256 J/g. Calculate the external work and

the increase in internal energy. (Ans. W = 169 J, ΔU = 2087 J)

8) Calculate the fall in temperature of helium initially at 15 oC when it is suddenly

expanded to 8 times its original volume (𝛾 = 5/3). (Ans. – 216.01 oC)

9) A cylinder containing one gram molecule of the gas was compressed adiabatically

until its temperature rose from 27 oC to 97 oC. Calculate the work done and heat

produced in the gas (𝛾 = 1.5). (Ans. W = −11.63 × 10􀬶 J and Q = 277 cal)

Long Answer ( LA) ( 4 marks Each)

1) State first law of thermodynamics and derive the relation between the change in

internal energy (ΔU), work done (W) and heat (Q).

2) Explain work done during a thermodynamic process.

3) Explain thermodynamics of isobaric process.

4) Explain thermodynamics of isochoric process.

5) Explain thermodynamics of adiabatic process.