AQA GCSE Electrical Power(Physics)

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Electrical Power

Electrical power is the rate of energy transfer. 

There are different equations for working with electrical power

Power = energy transferred over time, with formulae triangle and 3 rearrangments

Example question

A 5W light bulb is switched on for 2 minutes, calculate the energy transferred. 

Convert the 2 minutes into seconds. 2 minutes = 120 seconds

Energy = Power x time

Energy = 5W x 120 seconds

Energy = 600J

Formula for power = potential difference x current, including formulae triangle, units and rearrangements

Example calculation

1. A mains kettle uses 2300W and 230V. 

(a)Calculate the current that kettle uses for normal use.

P = V x I

I = P/V

I = 2300/230 = 10A

Power = current squared x resistance

 Example calculation

1. A tumble dryer has a current of 11A flowing and a resistance of 20 ohms. Calculate the power of the tumble dryer.

P = I2 x R

P = 112 x 20

P = 2420W

Practice Questions

1.An electric heater uses 12.9kJ of energy whilst switched on and has a power rating of 600W. Calculate how long the heater was switched on for.

2.A 3kW kettle draw a current of 12A from the mains supply. Calculate the potential difference of the mains supply

3.A dishwasher has a power rating of 1.2kW  and a resistance of 40Ω. Calculate the current flowing through the dishwasher.

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