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The first law of thermodynamics is written ΔQ = ΔU + ΔW and an isothermal process keeps temperature constant, so this Class 11 sheet opens with the energy accounting and its constant condition. The answers record thermal equilibrium and the efficiency 1 − T₂/T₁.
Key Takeaways
The first law is ΔQ = ΔU + ΔW (Q1).
An isothermal process keeps temperature constant (Q2).
Q6 records 1 − T₂/T₁ as the efficiency.
Section A: Multiple Choice Questions (1 Mark Each)
Choose the correct option for each question.
1.
The first law of thermodynamics is expressed as
(a) ΔQ = ΔU + ΔW (b) ΔQ = ΔU - ΔW (c) ΔU = ΔQ + ΔW (d) ΔW = ΔQ + ΔU
2.
In an isothermal process, the quantity that remains constant is
(a) Pressure (b) Temperature (c) Volume (d) Internal energy
3.
In an adiabatic process, the heat exchanged with the surroundings is
(a) Positive (b) Negative (c) Zero (d) Constant
4.
The zeroth law of thermodynamics establishes the concept of
(a) Thermal equilibrium (b) Heat engines (c) Entropy (d) Conservation of energy
5.
In an isochoric process, the quantity that remains constant is
(a) Pressure (b) Volume (c) Temperature (d) Heat
6.
The efficiency of a Carnot engine working between temperatures T₁ (hot) and T₂ (cold) is
(a) 1 - T₂/T₁ (b) 1 - T₁/T₂ (c) T₂/T₁ (d) 1 + T₂/T₁
Section B: Short Answer Type Questions (2 Marks Each)
Show all steps clearly.
7.
Write the mathematical statement of the first law of thermodynamics.
8.
In which thermodynamic process does temperature remain constant?
9.
In which thermodynamic process is no heat exchanged with the surroundings?
10.
Write the formula for the efficiency of a Carnot engine.
11.
State the zeroth law of thermodynamics.
12.
In which thermodynamic process does volume remain constant?
13.
Write the expression for the work done during the isothermal expansion of an ideal gas.
14.
What does the second law of thermodynamics state about the direction of heat flow?
Section C: Numericals & Word Problems (3 Marks Each)
Apply the concepts to solve the problems. Show all working.
15.
A gas absorbs 200 J of heat and does 120 J of work. Find the change in its internal energy.
16.
A Carnot engine works between 500 K and 300 K. Find its efficiency.
17.
300 J of work is done on a gas and its internal energy increases by 300 J. Find the heat exchanged.
18.
In a cyclic process, a gas does 400 J of work. Find the heat absorbed by the gas.
19.
A Carnot engine has an efficiency of 50%. If the hot reservoir is at 600 K, find the temperature of the cold reservoir.
20.
500 J of heat is given to a gas at constant volume. Find the change in its internal energy.
Answer Key
1. a) ΔQ = ΔU + ΔW
2. b) Temperature
3. c) Zero
4. a) Thermal equilibrium
5. b) Volume
6. a) 1 - T₂/T₁
7. Refer to solution guide.
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End of Worksheet
People Also Ask
How is the first law of thermodynamics written?
ΔQ = ΔU + ΔW, option (a) in this worksheet (Q1).
What stays constant in an isothermal process?
Temperature, option (b) in this worksheet (Q2).
What is the Carnot efficiency?
1 − T₂/T₁, option (a) in this worksheet (Q6).