Question

Two bodies each of mass $M$ and temperature independent specific heat $C$ are initially at temperatures $100K$ and $400K$. A reversible engine is used to extract heat with the hotter body as the source and cooler body as the sink. Both the bodies attain the same final temperature. Then

• A. The final temperature of the two bodies is $250K$
• B. The work done by the engine is $100MC$
• C. Total change in entropy of the system is zero
• D. The total heat extracted from the hotter body is $150MC$

Answer 1

Answer: (A), (C)

The correct options are
A The final temperature of the two bodies is $250K$
C Total change in entropy of the system is zero

If $TK$ is the final temperature then,

$MC(400-T)=MC(T-100)$

$400-T=T-100$

$\therefore T=250K$

As the engine is reversible.So, total change in entropy of the system is zero.