In this lesson, we will learn how to calculate the efficiency of electrical devices given their useful energy output and total energy output.
Sample Question Videos
Worksheet: 13 Questions • 4 Videos
A 60 W incandescent light bulb is left on for 30 seconds. In that time, it is supplied with 1,800 J of energy but it only converts 36 J of energy to light. What is the efficiency of the bulb?
An LED light has an efficiency of 29%. If it converts 5 800 J to light, what is the total energy it was supplied with?
A 1.8 kW kettle has an efficiency of 0.92. It is used to boil 1.3 kg of water, which requires 440 kJ of energy. How many minutes does it take the kettle to boil the water? Give your answer to the nearest minute.