Practice <strong>NEET UG Physics</strong> MCQ questions covering Mechanics, Thermodynamics, Waves & Optics, Modern Physics, Electricity & Magnetism, and Electromagnetic Induction. Aligned with NCERT Class 11 & 12 Physics syllabus.
At absolute zero, the entropy of a perfect crystal is:
Answer: B
According to third law of thermodynamics, entropy of a perfect crystal at 0 K is zero.
Q.102Easy
In an isochoric process, the work done by the gas is:
Answer: C
In isochoric (constant volume) process, W = ∫PdV = 0 since dV = 0
Q.103Medium
A reversible engine and an irreversible engine operate between the same two temperatures. Which has greater efficiency?
Answer: A
Carnot (reversible) engine has maximum efficiency between any two temperatures. All real irreversible engines are less efficient.
Q.104Medium
The heat capacity at constant pressure (Cp) for an ideal gas is greater than at constant volume (Cv) because:
Answer: B
At constant P, heat goes into both increasing internal energy and doing work: Q_p = ΔU + W. At constant V, heat only increases internal energy: Q_v = ΔU. Thus Cp > Cv by R.
Q.105Medium
For one mole of ideal gas, Cp - Cv equals:
Answer: B
Mayer's relation: Cp - Cv = R for one mole of ideal gas (in terms of molar heat capacities)
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Q.106Hard
Two identical gases at different temperatures are mixed adiabatically. The total entropy of the system:
Answer: B
Mixing is an irreversible adiabatic process. By second law, entropy of isolated system increases.
Q.107Easy
A gas expands from volume V to 2V at constant pressure P. The work done by the gas is:
Answer: C
Work in isobaric process: W = P(V_f - V_i) = P(2V - V) = PV
Q.108Hard
A substance undergoes a phase transition from solid to liquid at constant temperature and pressure. During this process:
Answer: C
Phase transition increases disorder, so entropy increases. Q = TΔS, and since T is constant and Q > 0, ΔS > 0.
Q.109Hard
In a throttling process (Joule-Thomson expansion), a real gas undergoes isenthalpic expansion. The temperature change depends on:
Answer: C
Joule-Thomson coefficient μ = (∂T/∂P)_H depends on gas properties. ΔT = μ × ΔP for throttling process.
Q.110Easy
A gas undergoes an adiabatic compression. Which statement is correct?
Answer: B
In adiabatic compression, Q=0. Work is done ON the gas (W<0), so ΔU = Q - W = -W > 0. Internal energy increases, causing temperature to rise.
Q.111Easy
For a cyclic process, which of the following is always true?
Answer: A
In a cyclic process, the system returns to its initial state, so ΔU = 0. By first law: Q = ΔU + W = W.
Q.112Easy
A Carnot engine operates between 300 K and 600 K. Its efficiency is:
