The internal energy of an ideal gas depends only on: MCQ with Answer and Explanation

The internal energy of an ideal gas depends only on:
A. Both pressure and volume
B. Volume
C. Temperature
D. Pressure
Answer: Option C
Solution (By JKExamLibrary)
For an ideal gas, internal energy U depends solely on temperature (U = f/2 nRT, where f is degrees of freedom). This follows from kinetic theory: no intermolecular forces, so energy is purely kinetic, proportional to T. Pressure and volume can change at constant T (isothermal process) without changing U. Memory tip: 'Ideal gas: U = U(T) only; real gases have volume dependence'. This thermodynamics concept is frequently tested in competitive exams. Always distinguish ideal vs real gas behavior; competitive exams typically assume ideal gas unless specified.

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Practice More Physics Questions

Question #1
The device used to increase or decrease AC voltage is
A. Transformer
B. Rectifier
C. Motor
D. Generator

Correct Answer: Option A


Explanation:
Transformer changes AC voltage.

This question belongs to: Science Physics
Question #2
Torricelli's Law states that the velocity of efflux of a fluid through a sharp-edged hole at the bottom of a tank filled to a depth 'h' is identical to:
A. The terminal velocity of the fluid.
B. The velocity of a sound wave in that fluid.
C. The velocity acquired by a freely falling body dropped from height 'h'.
D. The critical velocity for turbulent flow.

Correct Answer: Option C


Explanation:
Torricelli's Law is a direct application of Bernoulli's principle. It proves mathematically that the velocity of fluid exiting a small hole (efflux velocity v) is v = sqrt(2gh). This is exactly the same velocity a solid body would acquire if it fell freely under gravity from rest over the same vertical height 'h'.

This question belongs to: Science Physics
Question #3
If the momentum of a body is increased by 100%, its kinetic energy increases by
A. 300%
B. 200%
C. 100%
D. 400%

Correct Answer: Option A


Explanation:
Kinetic energy K = p²/(2m). If p becomes 2p (100% increase), K' = (2p)²/(2m) = 4p²/(2m) = 4K. So increase = 4K - K = 3K, i.e., 300% increase. Common mistake: think linear. Remember quadratic relationship. Percent increase = (new-old)/old × 100% = (4K-K)/K ×100 = 300%.

This question belongs to: Science Physics