Question

In a heat engine, Qh and Qc represents high temperature substance and low temperature substance respectively. Which of the following expressions is correct for the efficiency of the heat engine?

Answer 1

The efficiency of a heat engine is given by the expression
`eff =(Q_h-Q_c)/(Q_h)`

The efficiency of a heat engine is the ratio of the work done by the engine to the heat given as the input to the engine.

`eff =(W)/(Q_h)`

The heat engine absorbs Q h from the hot reservoir , performs a work W on the absorbed heat and rejects Qc to the cold reservoir.

Therefore, the work done is given by,

`W=Q_h - Q_c`

Thus the efficiency is given by,
`eff =(Q_h-Q_c)/(Q_h)`