Page 132 - York Global Science 6 - Physical Science

How do we know this? How can we measure how much electrical energy is

transferred in different appliances?

The amount of electrical energy an appliance transfers depends on the power
rating of the appliance.

The power rating of an appliance is measured in watts (W) or kilowatts (kW).

1000 W = 1 kW
• An appliance with a power rating of 1 watt needs 1 joule of energy every

second to work.
• An appliance with a power rating of 8 watts needs 8 joules of energy every
second.

Some appliances are more powerful and use lots of energy per second, so
their power rating is measured in kilowatts.

Try This!

Put these appliances in order of how much energy they use, from the most to
the least.

3000 W 80 W 900 W

2000 W 120 W

To really understand how much energy an appliance uses, we need to know
how much power it needs and how much time it is used for. Some appliances

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