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→Key Stage 3
: [[Energy]] ([[kilowatt-hour]]s) = [[Power]] ([[kilowatt]]s) x [[time]] ([[hour]]s)
: A '''kilowatt-hour''' is 3,600,000 [[Joule]]s.
===Energy Usage of Appliances===
: The amount of [[energy]] an '''appliance''' uses depends on the power rating and how long the '''appliance''' is used for.
: [[Energy]] usage for '''appliances''' is measured in [[kilowatt-hour]]s. This means all [[power]] ratings need to be in [[kilowatt]]s and time should be in [[hour]]s.
: [[Energy]] can be calculated with the equation: [[Energy]] = [[Power]] x [[time]]
{| class="wikitable"
|+ The Power ratings of some electrical appliances.
|-
| style="height:20px; width:250px; text-align:center;" |'''Filament Bulb'''
A 60[[Watt]] filament bulb may be used for 8 hours a day. Calculate the [[energy]] in kilowatt-hours.
| style="height:20px; width:250px; text-align:center;" |'''Energy Saving Bulb'''
A 25[[Watt]] energy saving bulb may be used for 8 hours a day. Calculate the [[energy]] in kilowatt-hours.
| style="height:20px; width:250px; text-align:center;" |'''Kettle'''
A 2000[[Watt]] kettle may be used for 30 minutes a day. Calculate the [[energy]] in kilowatt-hours.
|-
| style="height:20px; width:250px; text-align:left;" |
: Power = 60W = 0.060kW
: Time = 8 hours
: Energy = Power x time
: Energy = 0.060 x 8
: Energy = 0.48kilowatt-hours
| style="height:20px; width:250px; text-align:left;" |
: Power = 25W = 0.025kW
: Time = 8 hours
: Energy = Power x time
: Energy = 0.025 x 8
: Energy = 0.20kilowatt-hours
| style="height:20px; width:250px; text-align:left;" |
: Power = 2000W = 2.0kW
: Time = 30 minutes = 0.5hours
: Energy = Power x time
: Energy = 2.0 x 0.5
: Energy = 1.0kilowatt-hours
|-
| style="height:20px; width:250px; text-align:center;" |'''Television'''
A 250[[Watt]] television is left on for 3 hours each day. Calculate the [[energy]] in kilowatt-hours.
| style="height:20px; width:250px; text-align:center;" |'''Refrigerator'''
A 200[[Watt]] refrigerator is on for 24 hours each day. Calculate the [[energy]] in kilowatt-hours.
| style="height:20px; width:250px; text-align:center;" |'''Oven'''
A 2500[[Watt]] oven is used for 45 minutes each day. Calculate the [[energy]] in kilowatt-hours.
|-
| style="height:20px; width:250px; text-align:left;" |
: Power = 250W = 0.25kW
: Time = 3 hours
: Energy = Power x time
: Energy = 0.25 x 3
: Energy = 0.75kilowatt-hours
| style="height:20px; width:250px; text-align:left;" |
: Power = 200W = 0.20kW
: Time = 24 hours
: Energy = Power x time
: Energy = 0.20 x 24
: Energy = 4.8kilowatt-hours
| style="height:20px; width:250px; text-align:left;" |
: Power = 2500W = 2.5kW
: Time = 45 minutes = 0.75 hours
: Energy = Power x time
: Energy = 2.5 x 0.75
: Energy = 1.875kilowatt-hours
|}