P1- 3.3

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P1- 3.3- USING ELECTRICAL ENERGY

For any appliance the energy supplied depends on:

- How long it is used for

- The power supplied to it

THE ENERGY SUPPLIED TO A 1KW APPLIANCE IN 1 HOUR IS 1 KILOWATT-HOUR (kWh)

We can use the kilowatt hour as the unit of energy supplied by mains electricity.

You can use the equation to work out the energy supplied in a certain amount of time:

E= P X t

E= Energy transferred in kilowatt hours kWh

P= The power in kilowatts kW

T= The time taken for energy to be transferred in hours

TO WORK OUT THE POWER:

P= E divided by T

You can use this to work out energy transferred in joules aswell:

E= P x t

E= Energy transferred in Joules J

P= Power in watts W

T= Time taken for energy to be transferred in seconds S

The ELECTRICITY METER in your home measures how much electrical energy your family uses

We use kilowatt-hours to work out the cost of electricity

TOTAL COST= NUMBER OF KWH USED X COST PER KWH