A 2 kg mass attached to a spring (k = 200 N/m) oscillates on a frictionless surface. What is the period of oscillation?

The correct answer is B: 0.628 s. T = 2π√(m/k) = 2π√(2/200) = 2π√(0.01) = 2π(0.1) ≈ 0.628 s

An electric dipole (moment p) is placed in a non-uniform electric field. It experiences:

The correct answer is C: Both force and torque. In non-uniform field: τ = p × E (torque), and F = ∇(p·E) (net force). In uniform field, only torque.

The speed of light in a medium is 2×10⁸ m/s. What is the refractive index of the medium?

The correct answer is B: 1.5. n = c/v = (3×10⁸)/(2×10⁸) = 1.5

The current density in a conductor depends on:

The correct answer is C: Electric field and properties of conductor. Current density J = σE = neE, where σ is conductivity. It depends on both electric field and material properties (conductivity).

When a superconductor is cooled below its critical temperature, its resistance becomes zero. What is the effect on current flowing through it when connected to a constant voltage source?

The correct answer is A: Current becomes infinite. With R = 0, by I = V/R, current becomes infinite. In practice, voltage source cannot be maintained across a superconductor

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JEE Physics
Thermodynamics

Physics questions for JEE Main — Mechanics, Electrostatics, Optics, Modern Physics.

27 Q 9 Topics Take Mock Test

Difficulty: All Easy Medium Hard 21–27 of 27

Topics in JEE Physics

All Mechanics 100 Thermodynamics 100 Electrostatics 100 Current Electricity 100 Magnetism 100 Optics 100 Modern Physics 100 Semiconductors 100 Waves 100

Q.21 Easy Thermodynamics

For a diatomic ideal gas at room temperature, what is the ratio γ = Cₚ/Cᵥ?

A γ = 1.40

B γ = 1.67

C γ = 1.33

D γ = 1.50

Correct Answer: A. γ = 1.40

EXPLANATION

For diatomic gas: Cᵥ = (5/2)R and Cₚ = (7/2)R. γ = Cₚ/Cᵥ = 7/5 = 1.40

Test

Q.22 Easy Thermodynamics

What is the Clausius statement of the second law of thermodynamics?

A Heat cannot spontaneously flow from a colder body to a hotter body without external work

B Entropy of an isolated system always increases

C No heat engine can be 100% efficient

D Internal energy is a state function

Correct Answer: A. Heat cannot spontaneously flow from a colder body to a hotter body without external work

EXPLANATION

Clausius statement: Heat cannot spontaneously transfer from a colder body to a hotter body without external work being done on the system

Test

Q.23 Easy Thermodynamics

In an isochoric process for an ideal gas, what is the relationship between pressure and temperature?

A P/T = constant

B P×T = constant

C P = T

D P/T² = constant

Correct Answer: A. P/T = constant

EXPLANATION

For isochoric process (constant volume): PV = nRT with V constant gives P/T = nR/V = constant (Gay-Lussac's Law)

Test

Q.24 Easy Thermodynamics

What is the relationship between Cₚ and Cᵥ for an ideal gas?

A Cₚ = Cᵥ + R

B Cₚ = Cᵥ - R

C Cₚ = 2Cᵥ

D Cₚ/Cᵥ = constant

Correct Answer: A. Cₚ = Cᵥ + R

EXPLANATION

Mayer's relation: Cₚ - Cᵥ = R for one mole of ideal gas, hence Cₚ = Cᵥ + R

Test

Q.25 Easy Thermodynamics

For an ideal gas, internal energy depends on:

A Only temperature

B Only volume

C Both pressure and volume

D Pressure, volume, and temperature equally

Correct Answer: A. Only temperature

EXPLANATION

For an ideal gas, internal energy U depends only on temperature (U = nCᵥT), not on pressure or volume independently

Test

Q.26 Easy Thermodynamics

What is the first law of thermodynamics?

A ΔU = Q - W

B ΔU = Q + W

C Q = W + ΔU

D W = ΔU + Q

Correct Answer: B. ΔU = Q + W

EXPLANATION

The first law states: ΔU = Q + W, where ΔU is change in internal energy, Q is heat absorbed, and W is work done on the system

Test

Q.27 Easy Thermodynamics

A Carnot engine operates between temperature reservoirs of 500 K and 300 K. What is its maximum efficiency?

A 0.40 or 40%

B 0.60 or 60%

C 0.33 or 33%

D 0.50 or 50%

Correct Answer: A. 0.40 or 40%

EXPLANATION

Carnot efficiency: η = 1 - (Tc/Th) = 1 - (300/500) = 1 - 0.60 = 0.40 or 40%

Test

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