Efficiency of heat engine cycle is the ratio of

Efficiency of heat engine cycle is the ratio of

a. total heat input to the cycle (Q_in) to net work output of the cycle (W_net)
b. net work output of the cycle (W_net) to total heat input to the cycle (Q_in)
c. net work output of the cycle (W_net) to heat rejected from the system (Q_out)
d. none of the above

Correct Answer : a. total heat input to the cycle (Q_in) to net work output of the cycle (W_net)

Explanation :

In heat engine cycle, the heat is transferred to the system and work is transferred from the system. The main function of heat engine is to produce work output continuously by consuming heat energy given to the system. So the net work (W_net) and heat supplied (Q_in) to the system are taken into account. The net work output is the difference between work produces in the process and the work input required to take the system to initial state. In stem power plant, net work output is,
Turbine Work (W_T) – Pump Work (W_P)
Therefore, the efficiency of heat engine cycle is the ratio of total heat input to the cycle (Q_in) to net work output of the cycle (W_net).