Question

If the temperatures of source and sink of a cannot engine having efficiency 1 are each decreased' by 100 K, then the efficiency

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

Answer 1

Answer: (D)

increases

In starting the efficiency
$\eta =1-\frac{T_2}{T_1}=\frac{T_1-T_2}{T_1}$
On decreased by 100 K each the efficiency
$\eta =1-\frac{T_2-100}{T_1-100}=\frac{T_1-T_2}{T_1-100}$
In this case the efficiency will increases.