Question

A fan that is switched on for 1 minute uses 500 W usefully but also wastes 300 W through the emission of sound and heat. What's the efficiency of the fan?

Answer 1

Explanation:

Efficiency is defined as the ratio between the useful output over the total amount consumed. $E = \frac{useful}{total}$

The fan does 500W of useful work while wasting 300 W. The total power consumption is 800 W (500 + 300).