Question

A reversible engine takes heat from a reservoir at ${527}^o$ C and gives out heat to a sink at ${127}^o$ C. How many Joules/s must it take from the reservoir to perform useful mechanical work at the rate of $750W$?

• A. $257.14$
• B. $1500$
• C. $457.14$
• D. $557.14$

Answer 1

The correct option is B $1500$

Efficiency of a reversible heat engine is given by
$\eta =1-\frac{T_c}{T_h}=\frac{W}{Q_h}$
$⟹1-\frac{400}{800}=\frac{750}{Q_h}$
$⟹0.5=\frac{750}{Q_h}$
$\therefore Q_h=\frac{750}{0.5}=1500J/s$