Free Thermal Equilibrium and Heat MCQs with Answers
277 Thermal Equilibrium and Heat MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Thermal equilibrium means that bodies in contact have the same temperature and no net heat flows between them. The topic distinguishes heat from temperature, uses the zeroth law of thermodynamics, and covers heat transfer, specific heat capacity, thermal expansion and the conditions for reaching equilibrium.
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277 questions · page 5 of 14
- A. Positive
- B. Negative
- C. Zero
- D. Infinite
Explanation: For a reversible process, the total entropy change of the universe (system + surroundings) is zero, as entropy gained by the system is…
Correct answer: Zero- A. 5
- B. 6
- C. 4
- D. 3
Explanation: The COP of a refrigerator is given by COP = Tcold / (Thot - Tcold ), where Tcold = 250 K and Thot = 300 K.
Correct answer: 5- A. 5000 J
- B. 10000 J
- C. 2000 J
- D. 2500 J
Explanation: Heat required is Q = m·c·ΔT, where m = 2 kg, c = 500 J/kg·°C, and ΔT = 10°C. Thus, Q = 2 × 500 × 10 = 10,000 J.
Correct answer: 10000 J- A. Constant pressure
- B. Constant volume
- C. Constant temperature
- D. Constant entropy
Explanation: In Carnot cycle, the isothermal expansion occurs at constant temperature, where the gas absorbs heat from a reservoir and expands while…
Correct answer: Constant temperature- A. Isothermal
- B. Isobaric
- C. Isochoric
- D. Impossible
Explanation: For an ideal gas (PV = nRT), constant temperature and pressure imply constant volume, which contradicts process with changing state.
Correct answer: Impossible- A. Carnot cycle
- B. Otto cycle
- C. Diesel cycle
- D. Rankine cycle
Explanation: The Carnot cycle provides the maximum possible efficiency for a heat engine operating between two given temperatures, as it consists of…
Correct answer: Carnot cycle87. The latent heat of fusion of ice at 0°C is 334 kJ/kg. The entropy change when 1 kg of ice melts is:
- A. 1226 J/K
- B. 334 J/K
- C. 1000 J/K
- D. 273 J/K
Explanation: Entropy change for a phase transition is ΔS = ΔH/T, where ΔH = 334 kJ/kg = 334,000 J/kg and T = 0°C = 273 K.
Correct answer: 1226 J/K- A. Heat is removed from the system
- B. Work is done on the system
- C. Heat is added at constant temperature
- D. Temperature decreases
Explanation: Entropy change is ΔS = Q/T for a reversible process at constant temperature.
Correct answer: Heat is added at constant temperature- A. 400 J
- B. 600 J
- C. 300 J
- D. 1000 J
Explanation: The maximum efficiency of a Carnot engine is η = 1 - (Tcold/Thot) = 1 - (300/500) = 0.4.
Correct answer: 400 J- A. Increases
- B. Decreases
- C. Remains constant
- D. Becomes zero
Explanation: In a reversible adiabatic process, no heat is exchanged (Q = 0), so the entropy change (ΔS = Q/T) is zero, and the system's entropy…
Correct answer: Remains constant- A. 4520 kJ
- B. 9040 kJ
- C. 2260 kJ
- D. 4180 kJ
Explanation: For the phase change from water to steam at 100°C, only latent heat is required (no temperature change). Heat = m·Lv = 2 × 2260 = 4520 kJ.
Correct answer: 4520 kJ- A. A downward sloping curve
- B. A straight vertical line
- C. An upward sloping curve
- D. A hyperbolic curve
Explanation: PV=nRT, where nRT are constants in isothermal process (no temperature change) so graph D is the valid answer.
Correct answer: A hyperbolic curve- A. Adiabatic
- B. Isobaric
- C. Isochoric
- D. Isothermal
Explanation: Isochoric :In isochoric process the volume remain same and the pressure increase with rise in temperature and the graph of isochoric…
Correct answer: Isochoric94. Maxwell's velocity distribution curve is given for two different temperature. For the given curves:
- A. T1 > T2
- B. T1 < T2
- C. T1 ≤ T2
- D. T1 = T2
Explanation: Higher is the temperature greater is the most probable velocity. Hence, this option is correct.
Correct answer: T1 < T2- A. Temperature difference
- B. Pressure difference
- C. Volume change
- D. Entropy change
Explanation: According to Fourier's law, heat transfer by conduction is proportional to the temperature difference across the material, driving the…
Correct answer: Temperature difference- A. Gases
- B. Liquids
- C. Metals
- D. Insulators
Explanation: Metals have high thermal conductivity due to free electrons that efficiently transfer heat, unlike gases, liquids, or insulators, which…
Correct answer: Metals- A. 334 J/K
- B. 1226 J/K
- C. 273 J/K
- D. 1000 J/K
Explanation: Entropy change for a phase transition is ΔS = ΔH/T, where ΔH = 334 kJ/kg = 334,000 J/kg and T = 0°C = 273 K.
Correct answer: 1226 J/K- A. 84,000 J
- B. -2000/4.2 J
- C. 2000/4.2 J
- D. -8400
Explanation: To calculate the heat absorbed by a substance, we can use the formula:q = m * C * ΔTWhere:q is the heat absorbed or released,m is the mass…
Correct answer: -8400- A. Δ𝛉 + 373
- B. Δ𝛉 + 273
- C. Δ𝛉 + 100
- D. Δ𝛉
- E. Δ𝛉 + 212
Explanation: The change in temperature in the kelvin and Celsius scale is the same hence the answer will be D.
Correct answer: Δ𝛉- A. 1/100
- B. 1/212
- C. 1/273.16
- D. 1/32
- E. 1/98
Explanation: The correct answer is that the Kelvin is defined as 1/273.16 of the thermodynamic temperature of the triple point of water.
Correct answer: 1/273.16