Q.1 Which of the following is a state function in thermodynamics?
Work
Heat
Internal Energy
Path Length
Explanation - Internal energy depends only on the state of the system, not on the path taken to reach that state, making it a state function.
Correct answer is: Internal Energy
Q.2 The Zeroth law of thermodynamics deals with:
Entropy of a system
Heat transfer between systems
Thermal equilibrium
Work done in a cyclic process
Explanation - The Zeroth law states that if two systems are in thermal equilibrium with a third system, they are in thermal equilibrium with each other.
Correct answer is: Thermal equilibrium
Q.3 Which process occurs at constant pressure?
Isochoric
Isobaric
Adiabatic
Isothermal
Explanation - Isobaric processes are carried out at constant pressure.
Correct answer is: Isobaric
Q.4 In an isothermal process, the internal energy change (ΔU) is:
Equal to work done
Zero
Equal to heat added
Negative
Explanation - In an isothermal process, temperature remains constant so internal energy, which depends on temperature, does not change.
Correct answer is: Zero
Q.5 The unit of entropy in the SI system is:
J/mol
J/K
J/K·mol
W/m²
Explanation - Entropy is measured in joules per kelvin (J/K) in the SI system.
Correct answer is: J/K
Q.6 The first law of thermodynamics is a statement of:
Conservation of momentum
Conservation of mass
Conservation of energy
Increase of entropy
Explanation - The first law relates heat added to the system, work done by the system, and change in internal energy, representing energy conservation.
Correct answer is: Conservation of energy
Q.7 Which of the following has the highest specific heat capacity?
Water
Iron
Aluminium
Mercury
Explanation - Water has a very high specific heat capacity of about 4186 J/kg·K, making it effective for thermal regulation.
Correct answer is: Water
Q.8 In an adiabatic process, which quantity remains constant?
Temperature
Pressure
Heat transfer
Volume
Explanation - An adiabatic process involves no exchange of heat between the system and surroundings, so heat transfer is zero.
Correct answer is: Heat transfer
Q.9 The efficiency of a Carnot engine depends on:
The type of working substance
Temperatures of source and sink
Pressure of working fluid
Volume of the system
Explanation - Carnot efficiency depends only on the temperatures of the hot and cold reservoirs, given by η = 1 - Tc/Th.
Correct answer is: Temperatures of source and sink
Q.10 In a cyclic process, the net change in internal energy is:
Positive
Negative
Zero
Infinite
Explanation - At the end of a cyclic process, the system returns to its initial state, so internal energy remains unchanged.
Correct answer is: Zero
Q.11 A heat engine receives 200 J of heat and does 120 J of work. The heat rejected is:
80 J
120 J
200 J
320 J
Explanation - Using the first law, Q = W + Q_rejected. Thus, Q_rejected = 200 - 120 = 80 J.
Correct answer is: 80 J
Q.12 Which of the following is a reversible process?
Heat transfer due to finite temperature difference
Free expansion of a gas
Carnot cycle
Friction between surfaces
Explanation - The Carnot cycle is an ideal reversible process with no losses due to friction or temperature gradients.
Correct answer is: Carnot cycle
Q.13 Which thermodynamic process has ΔU = 0?
Isothermal
Adiabatic
Isobaric
Isochoric
Explanation - In an isothermal process, temperature remains constant so internal energy, which depends on temperature, does not change.
Correct answer is: Isothermal
Q.14 In an isochoric process, the work done by the system is:
Maximum
Minimum
Zero
Equal to heat added
Explanation - Work done depends on change in volume. In an isochoric process, volume is constant, so work done is zero.
Correct answer is: Zero
Q.15 The second law of thermodynamics introduces the concept of:
Heat transfer
Entropy
Internal energy
Work done
Explanation - The second law defines entropy and explains why certain processes are irreversible.
Correct answer is: Entropy
Q.16 For an ideal gas, internal energy depends on:
Pressure
Volume
Temperature
Work done
Explanation - The internal energy of an ideal gas is solely a function of temperature, independent of pressure or volume.
Correct answer is: Temperature
Q.17 In the SI system, the unit of work is:
Watt
Newton
Joule
Calorie
Explanation - Work is measured in joules (J) in the SI system, where 1 J = 1 N·m.
Correct answer is: Joule
Q.18 The work done in a reversible adiabatic expansion of an ideal gas depends on:
Initial and final pressures only
Initial and final temperatures only
Initial and final volumes only
Initial and final states
Explanation - Work in a reversible adiabatic process depends on the complete initial and final states of the system.
Correct answer is: Initial and final states
Q.19 The relation PV^γ = constant is valid for:
Isothermal process
Adiabatic process
Isochoric process
Isobaric process
Explanation - This equation describes a reversible adiabatic process where γ is the ratio of specific heats (Cp/Cv).
Correct answer is: Adiabatic process
Q.20 In the SI system, the value of the universal gas constant R is:
8.31 J/mol·K
0.0821 L·atm/mol·K
1.38 × 10^-23 J/K
273 J/mol·K
Explanation - The universal gas constant R has a value of 8.31 J/mol·K in SI units.
Correct answer is: 8.31 J/mol·K
Q.21 Which thermodynamic quantity is always positive for an irreversible process?
Work
Heat
Entropy change
Internal energy change
Explanation - Entropy always increases for an irreversible process, as per the second law of thermodynamics.
Correct answer is: Entropy change
Q.22 In which of the following processes is no heat exchanged?
Isothermal
Isochoric
Adiabatic
Isobaric
Explanation - Adiabatic processes occur without any heat exchange between the system and surroundings.
Correct answer is: Adiabatic
Q.23 The Kelvin scale is based on which thermodynamic principle?
Zeroth law
First law
Second law
Third law
Explanation - The third law provides the foundation for absolute temperature measurement used in the Kelvin scale.
Correct answer is: Third law
Q.24 What is the thermal efficiency of a reversible heat engine working between 400 K and 300 K?
25%
33.3%
50%
75%
Explanation - Carnot efficiency = 1 - Tc/Th = 1 - (300/400) = 0.25 or 25%.
Correct answer is: 25%
Q.25 The ratio of Cp to Cv for an ideal monoatomic gas is:
1.33
1.4
1.67
2
Explanation - For a monoatomic ideal gas, γ = Cp/Cv = 5/3 = 1.67.
Correct answer is: 1.67