THERMODYNAMIC MCQS

🔥 THERMODYNAMICS - MDCAT TEST 🔥

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Time 15:00

Question 1

Heat is the form of:

a) Powerb) Workc) Energyd) Motion

Correct Answer: C) Energy
Explanation: Heat is a form of energy that transfers between systems due to temperature difference.

Question 2

Pressure of the gas depends upon:

a) Only on molecular speedb) Only on mass of moleculec) Only on number of molecules in a unit volumed) Number of molecules in a unit volume, mass and speed of molecule

Correct Answer: D
Explanation: From kinetic gas theory P = 1/3 ρv². Depends on mass, number density and speed.

Question 3

In the isothermal process, one of the following is constant:

a) Pressureb) Volumec) Temperatured) Heat energy

Correct Answer: C) Temperature
Explanation: In isothermal process temperature remains constant. PV = constant.

Question 4

A process in which no heat enters or leaves the system is called:

a) Isothermal processb) Adiabatic processc) Isochoric processd) Isobaric process

Correct Answer: B) Adiabatic process
Explanation: Q = 0 in adiabatic process. Example: Cloud formation.

Question 5

For a gas obeying Boyle’s law, if the pressure is doubled, the volume becomes:

a) Doubleb) One halfc) Four timesd) One fourth

Correct Answer: B) One half
Explanation: Boyle's law: P1V1 = P2V2. If P doubled, V becomes half.

Question 6

Gas law PV^γ = constant is for:

a) Isothermal processb) Adiabatic processc) Isobaric processd) Isochoric process

Correct Answer: B) Adiabatic process
Explanation: For adiabatic process PV^γ = constant where γ = Cp/Cv.

Question 7

Cloud formation in the atmosphere is example of:

a) Adiabatic processb) Isothermal processc) Isochoric processd) Isobaric process

Correct Answer: A) Adiabatic process
Explanation: Rising air expands and cools adiabatically, causing condensation.

Question 8

Boyle’s law holds for ideal gases in:

a) Isochoric processesb) Isobaric processesc) Isothermal processesd) Adiabatic processes

Correct Answer: C) Isothermal processes
Explanation: Boyle's law: P ∝ 1/V at constant temperature.

Question 9

Which one is true for internal energy?

a) Sum of all energies of moleculesb) It is a state functionc) Proportional to translational KEd) All are correct

Correct Answer: D) All are correct
Explanation: Internal energy includes all KE and PE and is a state function.

Question 10

The internal energy of an ideal gas is directly proportional to:

a) Potential energyb) Translational kinetic energyc) Vibrational kinetic energyd) None of these

Correct Answer: B) Translational kinetic energy
Explanation: For ideal gas U = (3/2)nRT which is translational KE only.

Question 11

Which one is correct relation?

a) CP + CV = γb) CP = 1 + R/CVc) γ = CP/CVd) CP = 1 - R/CV

Correct Answer: C) γ = CP/CV
Explanation: Ratio of specific heats is called adiabatic index γ.

Question 12

For a gas Cp is always greater than Cv because:

a) Cp < Cvb) Cp > Cvc) Cp = Cvd) None

Correct Answer: B) Cp > Cv
Explanation: Cp = Cv + R. Extra heat needed for expansion work at constant pressure.

Question 13

Numerical value of Boltzmann’s constant is:

a) 1.38 × 10^−31 J/Kb) 3.18 × 10^−31 J/Kc) 3.18 × 10^−23 J/Kd) 1.38 × 10^−23 J/K

Correct Answer: D) 1.38 × 10^−23 J/K
Explanation: k = 1.380649 × 10^-23 J/K. Links micro and macro physics.

Question 14

The first law of thermodynamics is an expression of:

a) Conservation of energyb) Conservation of massc) Heat deathd) Degradation of energy

Correct Answer: A) Conservation of energy
Explanation: ΔU = Q - W. Energy can neither be created nor destroyed.

Question 15

The amount of heat required to raise temperature of 1 kg by 1 K is called:

a) Specific heatb) Heat capacityc) Caloried) Joule

Correct Answer: A) Specific heat
Explanation: Specific heat c = Q/mΔT. Unit: J/kg.K

Question 16

For isothermal process:

a) Q = Ub) Q = Wc) U = Wd) U = -W

Correct Answer: B) Q = W
Explanation: For isothermal ΔU=0, so from 1st law Q=W.

Question 17

In adiabatic expansion:

a) ΔQ = ΔWb) ΔQ = ΔUc) ΔW = -ΔUd) None

Correct Answer: C) ΔW = -ΔU
Explanation: For adiabatic Q=0, so ΔU = -W. Work done comes from internal energy.

Question 18

0°C is equal to:

a) 32°Fb) 273 Kc) 373 Kd) 100°F

Correct Answer: A) 32°F
Explanation: 0°C = 32°F = 273.15K. Freezing point of water.

Question 19

SI unit of thermodynamic temperature is:

a) Kelvinb) Centigradec) Fahrenheitd) Celsius

Correct Answer: A) Kelvin
Explanation: Kelvin is SI unit and starts from absolute zero.

Question 20

Normal human body temperature 98.6°F =?

a) 37°Cb) 42°Cc) 55°Cd) 40°C

Correct Answer: A) 37°C
Explanation: C = (F-32)×5/9 = (98.6-32)×5/9 = 37°C

Question 21

Triple point of water is:

a) 373.16 Kb) 284.16 Kc) 300.16 Kd) 273.16 K

Correct Answer: D) 273.16 K
Explanation: At triple point solid, liquid and gas coexist. 0.01°C = 273.16K

Question 22

If sink temperature decreases, Carnot engine efficiency:

a) Decreasesb) Increasesc) Remains samed) First increases then decreases

Correct Answer: B) Increases
Explanation: η = 1 - T2/T1. If T2 decreases, efficiency increases.

Question 23

Area of PV diagram for Carnot cycle represents:

a) Instant workb) Average workc) Total workd) Work during one cycle

Correct Answer: D) Work during one cycle
Explanation: Area under PV diagram = net work done in one complete cycle.

Question 24

Carnot cycle is:

a) Reversibleb) Irreversiblec) Bothd) None

Correct Answer: A) Reversible
Explanation: Carnot cycle is ideal reversible cycle with maximum efficiency.

Question 25

Efficiency of diesel engine is about:

a) 50% to 60%b) 25% to 30%c) 35% to 40%d) 40% to 50%

Correct Answer: C) 35% to 40%
Explanation: Diesel engines are more efficient than petrol due to higher compression ratio.

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