In general terms, the efficiency of a system can be thought of as the output per unit input.

Which of the expressions is a good mathematical representation of efficiency e of any heat engine?

Where,

Qh: the absolute value (magnitude) of the heat absorbed from the hot reservoir during one cycle or during some time specified in the problem

Qc: the absolute value (magnitude) of the heat delivered to the cold reservoir during one cycle or during some time specified in the problem

W: the amount of work done by the engine during one cycle or during some time specified in the problem

A) e=QhW

B) e=QcQh

C) e=QcW

D) e=WQh

E) e=WQc

Efficiency e = W/Qh

Explanation:

As written above efficiency of a system is calculated as the output per unit input. For heat Engine, Efficiency is calculated by dividing the Work done by Engine by Heat absorbed from hot reservoir.

In theoretical terms The maximum efficiency of a heat engine (which no engine ever attains) is equal to the temperature difference between the hot and cold ends divided by the temperature at the hot end, each expressed in absolute temperature (Kelvin).

But in practical calculations, it is calculated as e = W/Qh, and we define the thermal efficiency, of any heat engine as the ratio of the work it does, W, to the heat input at the high temperature, Qh.