# StudySquare

# AQA A-level Physics Electric energy and power

This page covers the following topics:

1. Power, voltage and current

2. Power, current and resistance

3. Energy, power and time

The relationship between power, voltage and current is given by: Power = Voltage × Current.

Ohm's Law can be used with the relationship of power, voltage and current to come up with a different relationship betweeen power, current and resistance, given by P = I²R.

The energy transferred to an appliance can be related its power rating and amount of time for which it is switched on through the following formula: Power = Energy transferred/time.

# 1

A light bulb has a power rating of 100 W with a potential difference of 240 V across it. Calculate the current flowing through it.

# 2

A vacuum has a power rating of 1500 W. Given that there is a current of 12 A flowing through it, calculate the resistance flowing through it.

# 3

Given that the current through a laptop is 0.3 A and a resistance of 500 Ω, calculate the power rating of the laptop.

# 4

The power rating of a kettle is 2.5 kW. Calculate the amount of energy in Joules transferred to the kettle in 2 minutes.

# 5

An electric motor is used in a lift. Given that the power rating of the lift is 6500 W and the lift is carried up in 50 s, calculate the energy transferred in the motor.

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