CBSE Class 11 Physics Thermodynamics Worksheet Set A

Question. During melting of ice, its entropy
(a) increases
(b) decreases
(c) remains same
(d) cannot say

Answer: A

Question. Ice contained in a beaker starts melting when
(a) the specific heat of the system is zero
(b) internal energy of the system remains constant
(c) temperature remains constant
(d) entropy remains constant

Answer: C

Question. A uniform sphere is supplied heat electrically at the centre at a constant rate. In the steady state, steady temperatures are established at all radial locations r, heat flows outwards radial and is ultimately radiated out by the outer surface is otropically. In this steady state, the temperature gradient varies with radial distance r according to
(a) r^–1
(b) r^–2
(c) r^–3
(d) r–3/2

Answer: B

Question. In thermodynamic processes which of the following statements is not true?
(a) In an isochoric process pressure remains constant
(b) In an isothermal process the temperature remains constant
(c) In an adiabatic process PVg = constant
(d) In an adiabatic process the system is insulated from the surroundings

Answer: A

Question. For an ideal gas graph is shown for three processes. Process 1, 2 and 3 are respectively. 

(a) Isobaric, adiabatic, isochoric
(b) Adiabatic, isobaric, isochoric
(c) Isochoric, adiabatic, isobaric
(d) Isochoric, isobaric, adiabatic

Answer: D

Question. The efficiency of carnot engine when source temperature is T₁ and sink temperature is T₂ will be
(a) T₁-T₂/T₁
(b) T₂-T₁/T₂
(c) T₁-T₂/T₂
(d) T₁/T2

Answer: A

Question. In the equation PVγ = constant, the value of γ is unity. Then the process is
(a) isothermal
(b) adiabatic
(c) isobaric
(d) irreversible

Answer: A

Question. For adiabatic processes (Letters have usual meanings)
(a) P^γV = constant
(b) T^γV = constant
(c) TV^γ–1 = constant
(d) TV^γ = constant

Answer: C

Question. The gas law PV/T = constant is true for
(a) isothermal changes only
(b) adiabatic changes only
(c) both isothermal and adiabatic changes
(d) neither isothermal nor adiabatic change

Answer: C

Question. When heat is given to a gas in an isothermal change, the result will be
(a) external work done
(b) rise in temperature
(c) increase in internal energy
(d) external work done and also rise in temperature

Answer: A

Question. Which of the following processes is adiabatic ?
(a) Melting of ice
(b) Bursting of tyre
(c) Motion of piston of an engine with constant speed
(d) None of these

Answer: B

Question. Which of the following statements about a thermodynamic process is wrong ?
(a) For an adiabatic process Δ_Eint = – W
(b) For a constant volume process Δ_Eint = + Q
(c) For a cyclic process Δ_Eint = 0
(d) For free expansion of a gas Δ_Eint > 0

Answer: A

Question. Volume of one mole gas changes according to the V = a/T. If temperature change is DT, then work done will be
(a) RΔT
(b) – RΔT
(c) R/γ-1 ΔT
(d) R (γ – 1) ΔT

Answer: B

Question. Two Carnot engines A and B are operated in series. The engine A receives heat from the source at temperature T₁ and rejects the heat to the sink at temperature T. The second engine B receives the heat at temperature T and rejects to its sink at temperature T₂. For what value of T the efficiencies of the two engines are equal?
(a) T₁+T₂/2
(b) T₁-T₂/2
(c) T₁T₂
(d) √T₁T2

Answer: D

Question. The temperature of 5 moles of a gas which was held at constant volume was changed from 100º to 120ºC. The change in the internal energy of the gas was found to be 80 joule, the total heat capacity of the gas at constant volume will be equal to
(a) 8 joule per K
(b) 0.8 joule per K
(c) 4.0 joule per K
(d) 0.4 joule per K

Answer: C

Question. In changing the state of thermodynamics from A to B state, the heat required is Q and the work done by the system is W. The change in its internal energy is
(a) Q + W
(b) Q – W
(c) Q
(d) Q – W/2

Answer: B

Question. If ΔQ and ΔW represent the heat supplied to the system and the work done on the system respectively, then the first law of thermodynamics can be written as
(a) ΔQ = ΔU + ΔW
(b) ΔQ = ΔU - ΔW
(c) ΔQ = ΔW - ΔU
(d) ΔQ = –ΔW - ΔU

Answer: B

Question. The efficiency of a Carnot engine operating with reservoir temperatures of 100ºC and –23ºC will be
(a) 100+23/100
(b) 100-23/100
(c) 100+23/373
(d) 100-23/373

Answer: C

Question. The work done in which of the following processes is equal to the internal energy of the system?
(a) Adiabatic process
(b) Isothermal process
(c) Isochoric process
(d) None of these

Answer: A