Question

A thermally insulated rigid container contains an ideal gas at ${27}^{o}C$. It is fitted with a heating coil of resistance 50$\Omega$. A current is passed through the coil for 10 minutes by connecting it to a d.c. source of 10 V. The change in the internal energy is

• A. zero
• B. 300 J
• C. 600 J
• D. 1200 J

Answer 1

The correct option is D

1200 J

Heat produced is given by
$dQ=\frac{V^{2}t}{R}=\frac{(10{)}^2\times (10\times 60)}{50}=1200J$
Since the container is rigid, the change in volume dV = 0. Hence work done dQ = PdV = 0. From the first law of thermodynamics, the change in internal energy is dU = dQ - dW = dQ = 1200 J.