Question

A thermally insulated rigid container contains an ideal gas. It is heated through a resistance coil of 100$\Omega$ by passing a current of 1 A for five minutes, then change in internal energy of the gas is

• A. 0 KJ
• B. 30 KJ
• C. 10 KJ
• D. 20 KJ

Answer 1

Answer: (B)

30 KJ

Heat H supplied to the gas in container: $H=i^2\times R\times dt$
where is is the current in the resistor( 1A), R is the resistance( 100 $\Omega$ and dt is the duration of time( 5 mins= 300 secs)
$\therefore H=1^2\times 100\times 300=30000J=30kJ$
Since the container is rigid, no work is done when the the gas expands. $dW=0$ in the equation $dQ=dU+dW$

As the work done is 0 so $dQ=dU$

Then $\text{The change in internal energy is equal to =30kJ}$