The internal energy of an ideal gas depends only on:
A. Both pressure and volume
B. Temperature
C. Pressure
D. Volume
Answer: Option B
Solution (By JKSSB Mock Tests)
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.
Explanation:
Specific heat capacity c is defined as heat required to raise temperature of unit mass (1 kg in SI) by 1°C (or 1 K). Formula: Q = mcΔT. Option D describes specific heat in cgs units (cal/g°C), but SI definition uses kg. Options A and C describe latent heats. Memory aid: 'Specific heat = per kg per degree'. This precise definition is crucial for calorimetry problems. Competitive exams often test unit awareness (kg vs g) to distinguish careful students. Always note the mass unit in the definition context.
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