CBSE Class 11 Thermodynamics Worksheet A

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Question. Which of the following processes is reversible?
(a) Transfer of heat by conduction
(b) Transfer of heat by radiation
(c) Isothermal compression
(d) Electrical heating of a nichrome wire

Answer: C

Question. A gas has pressure P and volume V. It is now compressed adiabatically to 1/32 times the original volume. Given that (32)^1.4 = 128, the final pressure is (γ = 1.4)
(a) P/128
(b) P/32
(c) 32 P
(d) 128 P

Answer: D

Question. A system goes from A to B via two processes I and II as shown in figure. If ΔU₁ and ΔU₂ are the changes in internal energies in the processes I and II respectively, then
(a) relation between ΔU₁ and ΔU₂ can not be determined
(b) ΔU₁ = ΔU₂
(c) ΔU₁ < ΔU₂
(d) ΔU₁ > ΔU₂

Answer: B

Question. A gas at 27ºC and pressure of 30 atm. is allowed to expand to atmospheric pressure and volume 15 times larger. The final temperature of the gas is
(a) – 123ºC
(b) +123ºC
(c) 273ºC
(d) 373ºC

Answer: A

Question. A system changes from the state (P₁, V₁) to (P₂, V₂) as shown in the figure. What is the work done by the system? 

(a) 7.5 × 10₅ joule
(b) 7.5 × 10⁵ erg
(c) 12 × 10⁵ joule
(d) 6 × 10⁵ joule

Answer: C

Question. Choose the correct relation between efficiency h of a Carnot engine and the heat absorbed (θ₁) and released by the working substance (θ₂).
(a) η = 1+θ₂/θ₁
(b) η = 1+θ₁/θ₂
(c) η = 1-θ₁/θ₂
(d) η = 1-θ₂/θ₁

Answer: D

Question. Which of the following relations does not give the equation of an adiabatic process, where terms have their usual meaning?
(a) P^γT^1–γ = constant 
(b) P^1–γ T^γ = constant
(c) PV^γ = constant
(d) TV^γ–1 = constant

Answer: A

Question. A polyatomic gas (γ = 4/3) is compressed to 1/8th of its volume adiabatically. If its initial pressure is P₀, its new pressure will be
(a) 8P₀
(b) 16P₀
(c) 6P₀
(d) 2P0

Answer: B

Question. Monatomic, diatomic and polyatomic ideal gases each undergo slow adiabatic expansions from the same initial volume and same initial pressure to the same final volume. The magnitude of the work done by the environment on the gas is
(a) the greatest for the polyatomic gas
(b) the greatest for the monatomic gas
(c) the greatest for the diatomic gas
(d) the question is irrelevant, there is no meaning of slow adiabatic expansion

Answer: A

Question. Choose the incorrect statement related to an isobaric process.
(a) constant V/T=
(b) W = PDV
(c) Heat given to a system is used up in raising the temperature only.
(d) ΔQ > W

Answer: C

Question. Absolute zero is obtained from
(a) P–V graph
(b) P - 1/V graph
(c) P–T graph
(d) V–T graph

Answer: C

Question. An ideal gas heat engine operates in Carnot cycle between 227°C and 127°C. It absorbs 6 × 10⁴ cals of heat at higher temperature. Amount of heat converted to work is
(a) 4.8 × 10⁴ cal
(b) 6 × 10⁴ cal
(c) 2.4 × 10⁴ cal
(d) 1.2 × 10⁴ cal

Answer: D

Question. In the given (V – T) diagram, what is the relation between pressure P₁ and P₂ ? 

(a) P₂ > P₁
(b) P₂ < P₁
(c) P₂ = P₁
(d) Cannot be predicted

Answer: B

Question. Three moles of an ideal gas kept at a constant temperature at 300 K are compressed from a volume of 4 litre to 1 litre. The work done in the process is
(a) – 10368 J
(b) –110368 J
(c) 12000 J
(d) 120368 J

Answer: A

Question. A mass of ideal gas at pressure P is expanded isothermally to four times the original volume and then slowly compressed adiabatically to its original volume. Assuming γ to be 1.5, the new pressure of the gas is
(a) 2 P
(b) P
(c) 4 P
(d) P/2

Answer: A

Question. One mole of an ideal gas at temperature T was cooled isochorically till the gas pressure fell from P to p/n . Then, by an isobaric process, the gas was restored to the initial temperature. The net amount of heat absorbed by the gas in the process is
(a) nRT
(b) RT/n
(c) RT (1 – n^–1)
(d) RT (n – 1)

Answer: C

Question. At a given temperature the internal energy of a substance
(a) in liquid state is equal to that in gaseous state.
(b) in liquid state is less than that in gaseous state.
(c) in liquid state is more than that in gaseous state.
(d) is equal for the three states of matter.

Answer: B

Question. The pressure inside a tyre is 4 times that of atmosphere. If the tyre bursts suddenly at temperature 300 K, what will be the new temperature?
(a) 300 (4)^7/2
(b) 300 (4)^2/7
(c) 300 (2)^7/2
(d) 300 (4)–2/7

Answer: D

Question. A monatomic ideal gas expands at constant pressure, with heat Q supplied. The fraction of Q which goes as work done by the gas is
(a) 1
(b) 2/3
(c) 3/5
(d) 2/5

Answer: D

1. Can you design heat energy of 100% efficiency?

2. Does the working of an electric refrigerator defy second law of thermodynamics?

3. A Carnot engine absorb 6×10⁵ cal at 22°c calculate work done per cycle by the engine if it sink is at 127°c?

4. How does second law of thermodynamics explain expansion of gas?

5. Calculate difference in efficiency of a Carnot energy working between:-

1) 400K and 350K

2) 350K and 300K

6. Derive an expression for the work done during isothermal expansion?

7. Briefly describe a Carnot cycle and derive an expression for the efficiency of Carnot cycle?

Click on link below to download CBSE Class 11 Thermodynamics Worksheet A.