Question

An ideal heat engine working between temperature T_1­ and T₂ has an efficiency η, the new efficiency if both the source and sink temperature are doubled, will be

• A. $\frac{\eta}{2}$
• B. $\eta$
• C. $2\eta$
• D. $3\eta$

Answer 1

Answer: (B)

$\eta$

Answer 2

In first case $\eta_{1} = \frac{T_{1} - T_{2}}{T_{1}}$

In second case $\eta_{2} = \frac{2T_{1} - 2T_{2}}{2T_{1}}$

$= \frac{T_{1} - T_{2}}{T_{1}} = \eta$