Question

NA heat engine has an efficiency n.Temperatures of source and sink are each decreased by 100 K. The efficiency of the engine:

• A. increases
• B. decreases
• C. remains constant
• D. becomes 1

Answer 1

The correct option is A increases

Efficiency of heat engine,

$n=1-\frac{T_2}{T_1}=\frac{T_1-T_2}{T_1}$. . . . . .(1)

According to question,

$T_1\to T_1-100$

$T_2\to T_2-100$

New efficiency, $n^{\prime }=1-\frac{T_2-100}{T_1-100}$

$n^{\prime }=\frac{T_1-T_2}{T_1-100}$

From equation (1) and (2), we can conclude that

$n^{\prime }\propto \frac{1}{T_1-100}$

The efficiency of the engine is increases.

The correct option is A.