Question

The efficiency of a heat engine is maximum when:

• A. temperature of sink $>$ temperature of source
• B. temperature of source $>$ temperature of sink
• C. the difference between temperature of source and sink is very high
• D. none of these

Answer 1

The correct option is C the difference between temperature of source and sink is very high

The fraction of the heat absorbed by a machine that it can transform into work is called the efficiency of the machine $\eta$.
The efficiency of a heat engine is maximum when the difference between temperature of source and sink is very high
$\eta =\frac{T_2-T_1}{T_2}$
Here $T_2$ and $T_1$ are the temperatures of the source and sink respectively.