Energy Efficiency

Question 1

What is energy efficiency?

Answer 1

Efficiency is a measure of how good a device is at transferring energy from one store to another.

Question 2

True or False? Energy efficiency has units.

Answer 2

False, it does not have units. It’s a number between 0 and 1 which can be converted into a percentage by multiplying it by 100.

Question 3

What is the equation used to calculate energy efficiency?

Answer 3

Energy efficiency = Useful energy output / Total energy input

Question 4

A light bulb transfers 300J of energy electrically. It converts 180J to light by radiation and 120J to thermal energy. Calculate the efficiency of the light bulb.

Answer 4

Efficiency = 180 / 300
= 0.6 or 60%