Question

The temperature diagram of a entropy reversible engine cycle is given in the figure, its efficiency is

• A. 2/3
• B. 1/3
• C. 1/4
• D. 1/2

Answer 1

The correct option is D 1/2

$dQ=TdS$

Hence area under the curve gives the amount of heat exchanged.

Heat taken by system = Area of trapezium
Heat released by the system = Area of square

efficiency = work done/heat taken
= (Heat taken - Heat released)/Heat taken

$=\frac{(1.5TS-1TS)}{1TS}=\frac{1}{2}$
Increase in entropy means heat taken and vice-versa.