Question

If Q1 and Q2 are respectively the heat supplied and expelled by a system at a constant temperature, then the work done by the system is

• A. \( Q_1 - Q_2 \)
• B. \( Q_1 + Q_2 \)
• C. \( \frac{Q_1 - Q_2}{2} \)
• D. \( \frac{Q_2 - Q_1}{2} \)
• E. \( \frac{Q_1 + Q_2}{2} \)

Hint:

In an isothermal process, the work done is the difference between the heat supplied and the heat expelled by the system.

Answer 1

The Correct Option is A

In thermodynamics, when a system undergoes a process at constant temperature, the heat supplied to the system, \( Q_1 \), and the heat expelled from the system, \( Q_2 \), are related to the work done by the system. According to the first law of thermodynamics, for a process at constant temperature (isothermal process), the change in internal energy \( \Delta U = 0 \). Therefore, the work done by the system is the difference between the heat absorbed and the heat expelled: \[ W = Q_1 - Q_2 \] Thus, the correct answer is (A).