Question

During isothermal expansion at $800K$, the working substance of a Carnot engine releases $480cal$ of heat. If the sink is at $300K$, then the work done by the working substance during isothermal expansion will be

• A. $480cal$
• B. $300cal$
• C. $270cal$
• D. $190cal$

Answer 1

The correct option is B $300cal$

The efficiency of the cycle is given as $\eta =1-\frac{T_2}{T_1}=\frac{W}{Q_1}$. Here $T_1$ is the temperature of the source and $T_2$ is the temperature of the sink. $Q_1$ is the heat taken up from the source and $W$ is the work done in the process.

Thus, we get $\eta =1-\frac{300}{800}=\frac{5}{8}=\frac{W}{480}$
Thus we calculate $W$ as $300cal$