THERMODYNAMICS MCQ SET 7
Q1. The internal energy of an ideal gas is independent of:
A) Temperature
B) Pressure
C) Volume
D) Mass
Answer: C) Volume
Explanation: For an ideal gas, internal energy depends only on temperature.
Q2. Heat cannot flow from cold to hot body without external work โ this statement is given by:
A) Kelvin-Planck
B) Clausius
C) Joule
D) Boyle
Answer: B) Clausius
Explanation: Clausius statement of the second law describes the natural direction of heat flow.
Q3. The unit of the gas constant R is:
A) kJ/kgยทK
B) J/kgยทK
C) kJ/molยทK
D) J/molยทK
Answer: B) J/kgยทK
Explanation: In thermodynamics, R = 287 J/kgยทK for air (specific gas constant).
Q4. The temperature at which a pure substance changes phase is called:
A) Boiling point
B) Melting point
C) Saturation temperature
D) Critical temperature
Answer: C) Saturation temperature
Explanation: Itโs the temperature where phase change occurs at a given pressure.
Q5. The work done during an isothermal expansion of an ideal gas is given by:
A) W = nRT ln(Vโ/Vโ)
B) W = PฮV
C) W = mCโฮT
D) W = 0
Answer: A) W = nRT ln(Vโ/Vโ)
Explanation: Derived from the first law of thermodynamics for isothermal processes.
Q6. The property that measures the ability of a substance to transfer heat is:
A) Density
B) Conductivity
C) Entropy
D) Specific heat
ย Answer: B) Conductivity
Explanation: Thermal conductivity defines how easily heat passes through a material.
Q7. The lowest temperature possible is known as:
A) Freezing point
B) Triple point
C) Absolute zero
D) Zero Celsius
Answer: C) Absolute zero
Explanation: At 0 K, all molecular motion theoretically stops.
Q8. A system is said to be in thermodynamic equilibrium when:
A) Temperature is constant
B) Pressure is constant
C) Chemical composition is constant
D) All of the above
Answer: D) All of the above
Explanation: Thermal, mechanical, and chemical equilibrium must exist simultaneously.
Q9. The process in which both pressure and temperature change but volume remains constant is:
A) Isochoric
B) Isobaric
C) Isothermal
D) Polytropic
Answer: A) Isochoric
Explanation: Volume is constant while other properties may vary.
Q10. The work input to a heat pump is used to:
A) Absorb heat from the cold body
B) Reject heat to the cold body
C) Increase the internal energy
D) Reduce entropy
Answer: A) Absorb heat from the cold body
Explanation: A heat pump uses work to extract heat from a cold region and deliver it to a hot region.
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