A heat engine produces $300 \mathrm{~W}$ of mechanical power while discarding $1200 \mathrm{~W}$ into the environment (its cold reservoir). What is this engine's efficiency?
A) $\mathbf{0 . 2 0}$
B) 0.25
C) 0.33
D) Other (specify)

Question

Quizplus · Accepted Answer

The efficiency of a heat engine is given by the formula $\eta = \frac{W}{Q_{\text{in}}}$, where $W$ is the work output (mechanical power in this case) and $Q_{\text{in}}$ is the heat input. The heat input can be calculated as the sum of the work output and the heat discarded into the environment, which is $300 \mathrm{~W} + 1200 \mathrm{~W} = 1500 \mathrm{~W}$. Thus, the efficiency is $\eta = \frac{300}{1500} = 0.20$.

A Heat Engine Produces 300 W300 \mathrm{~W}300 W Of Mechanical Power While Discarding 1200 W1200 \mathrm{~W}1200 W

A Heat Engine Produces $300 \mathrm{~W}$ Of Mechanical Power While Discarding $1200 \mathrm{~W}$