Answers to AQA GCSE Calculations for Transformers (Physics)

Practice Questions

1. A transformer has 200 turns on the primary coil and 1000 turns on the secondary coil.If the input voltage is 240 V, calculate the output potential difference.

np = 200

Vp = 240

ns = 1000

Vs = (ns x Vp)/np

Vs = (1000 x 240)/200

Vs = 1200V

2. An electric toothbrush charges using a transformer. The charger is plugged into a 230 V mains socket and the coil inside the base has 920 turns. The coil inside the toothbrush has 40 turns.

What is the potential difference induced across the toothbrush coil?

np = 920

Vp = 230

ns = 40

Vs = (ns x Vp)/np

Vs = (40 x 230)/920

Vs = 10V

3.A machine in a factory requires 500 V to operate and is connected to a transformer coil with 1250 turns. The transformer’s other coil is connected to the 230 V supply.

How many turns are on the coil connected to the mains?

Vs = 500

Vp = 230

ns = 1250

np = (ns xVp)/Vs

Vs = (1250 x 230)/500

Vs = 575V

Accordion Content

Accordion Content