Physics is where JEE ranks are usually won or lost, since a single conceptual slip changes the whole answer. Questions here span mechanics, rotational motion, thermodynamics, waves and oscillations, electrostatics, current electricity, magnetism, optics, and modern physics. Numerical problems carry full derivations so you can see which step you skipped, not just which option was right.
In an isochoric process for an ideal gas, what is the relationship between pressure and temperature?
Answer: A
For isochoric process (constant volume): PV = nRT with V constant gives P/T = nR/V = constant (Gay-Lussac's Law)
Q.42Easy
What is the Clausius statement of the second law of thermodynamics?
Answer: A
Clausius statement: Heat cannot spontaneously transfer from a colder body to a hotter body without external work being done on the system
Q.43Easy
For a diatomic ideal gas at room temperature, what is the ratio γ = Cₚ/Cᵥ?
Answer: A
For diatomic gas: Cᵥ = (25)R and Cₚ = (27)R. γ = Cₚ/Cᵥ = 57 = 1.40
Q.44Easy
A thermodynamic system undergoes a process where internal energy increases by 150 J while the system does 100 J of work on surroundings. What is the heat absorbed by the system?
Answer: A
By first law: ΔU = Q - W. Here ΔU = 150 J, W = 100 J (work done by system). So Q = ΔU + W = 150 + 100 = 250 J
Q.45Easy
For one mole of an ideal monatomic gas, the ratio Cp/Cv is:
Answer: B
For monatomic gas: Cv = (23)R and Cp = (25)R. Therefore Cp/Cv = (25)/(23) = 35 ≈ 1.67
Q.46Easy
In an adiabatic process, if a gas is compressed, which statement is correct?
Answer: B
In adiabatic compression, no heat exchange occurs (Q=0). Work is done on the gas, so ΔU = W (positive). Since ΔU increases, temperature must increase.
Q.47Easy
A carnot engine operates between temperatures 500 K and 300 K. What is its maximum efficiency?
A system absorbs 500 J of heat and performs 200 J of work on the surroundings. What is the change in internal energy of the system?
Answer: A
By first law of thermodynamics: ΔU = Q − W = 500 − 200 = 300 J
Q.49Easy
An ideal gas undergoes an adiabatic process. If the gas is compressed, which of the following is true?
Answer: B
In adiabatic compression (Q = 0), work is done on the gas (W < 0). By first law: ΔU = Q − W = 0 − W > 0. Since ΔU ∝ ΔT for ideal gas, temperature increases.
Q.50Easy
What is the efficiency of a Carnot engine operating between 400 K and 300 K?
A system absorbs 4000 J of heat and does 1500 J of work. Change in internal energy is:
Answer: A
First law: ΔU = Q - W = 4000 - 1500 = 2500 J (where W is work done by system)
Q.57Easy
A gas expands adiabatically from state (P₁, V₁, T₁) to state (P₂, V₂, T₂). Which relation is correct for this process?
Answer: D
For adiabatic process: PV^γ = constant, TV^(γ-1) = constant, and T^γ P^(1-γ) = constant. All three relations are equivalent and correct.
Q.58Easy
The internal energy of an ideal gas depends only on:
Answer: C
For an ideal gas, internal energy U depends only on temperature (U = nC_vT). This is independent of pressure or volume, as shown by kinetic theory.
Q.59Easy
A thermodynamic system does 600 J of work while 2400 J of heat is supplied to it. What is the change in internal energy?
Answer: A
By first law of thermodynamics: ΔU = Q - W = 2400 - 600 = 1800 J (where W is work done by system)
Q.60Easy
A system absorbs 8000 J of heat and its internal energy increases by 5000 J. According to the first law of thermodynamics, what work is done by the system?
Answer: A
First law: ΔU = Q - W, so W = Q - ΔU = 8000 - 5000 = 3000 J (work done by the system)
