Topic Menu

Cyber-chess a chess instruction site

GCSE Questions: Energy Changes

Q2. The diagram shows a man using a leaf blower to move leaves.

The leaf blower is powered by an electric motor connected to a battery.

(a) Energy transfers take place when the leaf blower is being used. Complete the following sentences. [3 marks]

The battery stores chemical energy which is transferred into electrical energy.

The electric motor transfers electrical energy usefully into kinetic energy.

The motor wastes energy as sound and as energy that heats the surroundings.

(b) The diagram below is a Sankey diagram for the leaf blower.

Use the Sankey diagram to calculate the efficiency of the leaf blower. [2 marks]

Input is 8 squares

Output is 3 squares

Wasted is 5 squares

Efficiency = output/input = 3/8

= 0.375

(= 37.5% - that would get you the mark too!)

[Total 5 marks]