This chapter covers heat capacity, thermal expansion, thermal conductivity, gas laws, internal energy, adiabatic/isothermal processes, work done in expansion, entropy, Carnot engine efficiency, maximum density of water, and phase changes.
WBCS Mains Physics Heat & Thermodynamics Questions 2023
Q5. The degrees of freedom of H₂ molecule is
(A) 2
(B) 3
(C) 5
(D) 6
Correct Answer: (C) 5
Q52. OTEC involves thermal power generation from
(A) Sea
(B) River
(C) Wetland
(D) Lake
Correct Answer: (A) Sea
Q60. The internal energy of gas due to adiabatic expansion will be
(A) Decreased
(B) Increased
(C) Same
(D) Dissipated
Correct Answer: (A) Decreased
Q175. At constant temperature, the graph between P (pressure) vs 1/V (V = volume) of a real gas is
(A) Hyperbola
(B) Parabola
(C) Circle
(D) Straight line
Correct Answer: (D) Straight line
WBCS Mains Physics Heat & Thermodynamics Questions 2022
Q. Supercritical CO₂, held at or above its critical temperature and critical pressure, adopts properties:
(A) Midway between solid and gas
(B) Of liquid only
(C) Of gas only
(D) Midway between liquid and gas
Correct Answer: (D) Midway between liquid and gas.
Q. The process of rapid cooling of parts in metallurgical operations is called:
(A) Annealing
(B) Quenching
(C) Tempering
(D) Toughening
Correct Answer: (B) Quenching.
Q. The relationship between pressure (P) and volume (V) of a gas undergoing adiabatic expansion is:
(A) PV = Constant
(B) PV<sup>γ</sup> = Constant
(C) PV<sup>(γ−1)</sup> = Constant
(D) PV<sup>(1/γ)</sup> = Constant
Correct Answer: (B) PV<sup>γ</sup> = Constant.
Q. The ratio of specific heats at constant pressure and constant volume for a diatomic gas is:
(A) 1.66
(B) 1.40
(C) 1.30
(D) 1.25
Correct Answer: (B) 1.40.
WBCS Mains Physics Heat & Thermodynamics Questions 2021
Q. A refrigerator is:
(A) A heat engine
(B) An air-cooler
(C) An electric motor
(D) A heat engine working in reverse order
Correct Answer: (D) A heat engine working in reverse order.
Q. The latent heat of vaporization of a substance can be calculated from:
(A) van’t Hoff isotherm
(B) Clausius-Clapeyron equation
(C) Kirchhoff’s equation
(D) Gibbs-Helmholtz equation
Correct Answer: (B) Clausius-Clapeyron equation.
WBCS Mains Physics Heat & Thermodynamics Questions 2020
Q. The temperature, in the centigrade scale, at which the density of water is maximum is:
(A) 100°C
(B) 44°C
(C) 4°C
(D) 0°C
Correct Answer: (C) 4°C.
Q. In summer, a mild wind is often found on the shore of a calm river. This is caused due to:
(A) Difference in thermal conductivity of water and soil
(B) Convection currents
(C) Conduction between air and the soil
(D) Radiation from the soil
Correct Answer: (B) Convection currents.
Q. Which of the following parameters is the same for molecules of all gases at a given temperature?
(A) Mass
(B) Speed
(C) Momentum
(D) Kinetic energy
Correct Answer: (D) Kinetic energy.
Q. A metal sheet with a circular hole is heated. The hole:
(A) Gets larger
(B) Gets smaller
(C) Remains of the same size
(D) Gets deformed
Correct Answer: (A) Gets larger.
Q. The reading on the centigrade scale is −40. What is the corresponding reading on the Fahrenheit scale?
(A) −60°F
(B) −40°F
(C) 60°F
(D) 40°F
Correct Answer: (B) −40°F.
Q. The same mass of iron, copper, water and glycerine are heated to 80°C. Which substance will take the largest time to cool down to 20°C?
(A) Iron
(B) Copper
(C) Water
(D) Glycerine
Correct Answer: (C) Water.
Q. 10°C is equivalent to:
(A) 55°F
(B) 60°F
(C) 50°F
(D) 52°F
Correct Answer: (C) 50°F.
WBCS Mains Physics Heat & Thermodynamics Questions 2019
Q. In which of the following phenomena do heat waves travel along straight lines with the speed of light?
(A) Thermal conduction
(B) Forced convection
(C) Natural convection
(D) Thermal radiation
Correct Answer: (D) Thermal radiation.
WBCS Mains Physics Heat & Thermodynamics Questions 2018
Q. The relationship between temperature (T) and volume (V) of a gas undergoing adiabatic expansion is:
(A) TV = Constant
(B) TV<sup>γ</sup> = Constant
(C) TV<sup>(γ−1)</sup> = Constant
(D) T<sup>γ</sup>V = Constant
Correct Answer: (C) TV<sup>(γ−1)</sup> = Constant.
Q. The pressure-volume relation for a monoatomic gas undergoing adiabatic expansion is:
(A) PV<sup>5/3</sup> = Constant
(B) PV<sup>7/5</sup> = Constant
(C) PV<sup>4/3</sup> = Constant
(D) PV<sup>5/2</sup> = Constant
Correct Answer: (A) PV<sup>5/3</sup> = Constant.
Q. At 0 K, fluids are assumed to have:
(A) Minimum entropy
(B) Maximum entropy
(C) Zero entropy
(D) A fixed value of entropy
Correct Answer: (A) Minimum entropy.
Q. A Carnot engine operating between 27°C and 127°C has an efficiency of:
(A) 21%
(B) 22%
(C) 24%
(D) 25%
Correct Answer: (D) 25%.
Q. Water has maximum density at:
(A) Room temperature
(B) 0°C
(C) 4°C
(D) 100°C
Correct Answer: (C) 4°C.
Q. The quantity remaining constant during the isothermal expansion of an ideal gas is:
(A) Heat content
(B) Internal energy
(C) Pressure
(D) Pressure and Temperature
Correct Answer: (B) Internal energy.
WBCS Mains Physics Heat & Thermodynamics Questions 2017
Q. An internal combustion engine runs on the principle of:
(A) Otto cycle
(B) Diesel cycle
(C) Carnot cycle
(D) Rankine cycle
Correct Answer: (A) Otto cycle.
Q. Water attains maximum density at:
(A) 0°C
(B) 4°F
(C) 4 K
(D) 4°C
Correct Answer: (D) 4°C.
WBCS Mains Physics Heat & Thermodynamics Questions 2016
Q. A gas is enclosed in a container which is then placed on a fast-moving train. The temperature of the gas:
(A) Falls
(B) Rises
(C) Remains unchanged
(D) Becomes unsteady
Correct Answer: (C) Remains unchanged.
Q. When red glass is heated in a dark room, it will seem:
(A) Green
(B) Purple
(C) Black
(D) Yellow
Correct Answer: (D) Yellow.
Q. A refrigerator, with its power on, is kept in a closed room with its door open. The temperature of the room will:
(A) Fall
(B) Rise
(C) Remain the same
(D) None of the above
Correct Answer: (B) Rise.
Q. Cooking takes the longest time:
(A) At Shimla
(B) At Mt. Everest
(C) At sea level
(D) None of the above
Correct Answer: (B) At Mt. Everest.
Q. What is the principle by which a cooling system (radiator) in a motor car works?
(A) Convection
(B) Conduction only
(C) Radiation only
(D) Both conduction and radiation
Correct Answer: (A) Convection.
Q. Entropy change of a system and its surroundings in equilibrium:
(A) Increases
(B) Decreases
(C) Remains constant
(D) Either increases or decreases
Correct Answer: (C) Remains constant.
Q. Nights are cooler in deserts than in the plains because:
(A) Sand radiates heat more quickly than the earth
(B) The sky remains clear most of the time
(C) Sand absorbs heat more quickly than the earth
(D) None of the above
Correct Answer: (A) Sand radiates heat more quickly than the earth.
Q. Which of the following is a closed system?
(A) Jet engine
(B) Tea placed in a steel kettle
(C) Pressure cooker
(D) Rocket engine during propulsion
Correct Answer: (C) Pressure cooker.
WBCS Mains Physics Heat & Thermodynamics Questions 2015
Q. The total energy of a given mass of a gas at a given temperature depends on its:
(A) Pressure
(B) Volume
(C) Density
(D) Temperature
Correct Answer: (D) Temperature.
Q. A sample of gas expands from volume V1 to V2. The amount of work done by the gas is greatest when the expansion is:
(A) Adiabatic
(B) Equal in all cases
(C) Isothermal
(D) Isobaric
Correct Answer: (C) Isothermal.
Q. When water is heated from 0°C to 10°C, its volume:
(A) Increases
(B) Decreases
(C) Does not change
(D) First decreases and then increases
Correct Answer: (D) First decreases and then increases.
WBCS Mains Physics Heat & Thermodynamics Questions 2014
Q. Microwave ovens heat water in food because:
(A) Water is a polar molecule
(B) The heat capacity of water is high
(C) Water flows easily
(D) Water molecule is small
Correct Answer: (A) Water is a polar molecule.
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