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QPage 62: Q14: HC Verma: Concepts of Physics - Volume 2 Laws of Thermodynamics Page 62: Q14 Solution: The internal energy of an ideal gas decreases by the same…

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often incorrectly assume that a specific energy balance like $\Delta U = -W$ implies a unique process type (e.g., adiabatic), but for an ideal gas, internal energy is a state function dependent solely on temperature ($U \propto T$). Therefore, any decrease in internal energy strictly mandates a decrease in temperature, regardless of the path taken.

The internal energy of an ideal gas decreases by the same amount as the work done by the system.

Multiple Choice Options

  • A The process must be adiabatic.
  • B The process must be isothermal.
  • C The process must be isobaric.
  • D The temperature must decrease.

Step-by-Step Verified Solution

**Answer:** (d) The temperature must decrease. **Step-by-Step Explanation:** _U = -W. Since W > 0, _U < 0, so temperature decreases.

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