Difference between revisions of "Kilowatt-hour"
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: The '''kilowatt-hour''' is used by electricity suppliers instead of [[Joule]]s. | : The '''kilowatt-hour''' is used by electricity suppliers instead of [[Joule]]s. | ||
: A '''kilowatt-hour''' is calculated by multiplying the power rating of an appliance in [[kilowatt]]s by the time the appliance is used for in [[hour]]s. | : A '''kilowatt-hour''' is calculated by multiplying the power rating of an appliance in [[kilowatt]]s by the time the appliance is used for in [[hour]]s. | ||
| + | : A '''kilowatt-hour''' is 3,600,000 [[Joule]]s. | ||
| + | |||
| + | ===Equation=== | ||
: [[Energy]] ([[kilowatt-hour]]s) = [[Power]] ([[kilowatt]]s) x [[time]] ([[hour]]s) | : [[Energy]] ([[kilowatt-hour]]s) = [[Power]] ([[kilowatt]]s) x [[time]] ([[hour]]s) | ||
| − | : A '''kilowatt- | + | |
| + | ===Example Calculations=== | ||
| + | : 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 | ||
| + | |} | ||
| + | |||
| + | ===References=== | ||
| + | ====OCR==== | ||
| + | |||
| + | :[https://www.amazon.co.uk/gp/product/0198359837/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=0198359837&linkCode=as2&tag=nrjc-21&linkId=3c4229e8b023b2b60768e7ea2307cc6f ''Kilowatt-hour (kWh), pages 202, Gateway GCSE Physics, Oxford, OCR ''] | ||
Latest revision as of 16:24, 13 December 2019
Contents
Key Stage 3
Meaning
A kilowatt-hour is a unit of energy used for electrical appliances and in electrical bills.
About kilowatt-hours
- The kilowatt-hour is used by electricity suppliers instead of Joules.
- A kilowatt-hour is calculated by multiplying the power rating of an appliance in kilowatts by the time the appliance is used for in hours.
- A kilowatt-hour is 3,600,000 Joules.
Equation
Example Calculations
- 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-hours. This means all power ratings need to be in kilowatts and time should be in hours.
- Energy can be calculated with the equation: Energy = Power x time
| Filament Bulb
A 60Watt filament bulb may be used for 8 hours a day. Calculate the energy in kilowatt-hours. |
Energy Saving Bulb
A 25Watt energy saving bulb may be used for 8 hours a day. Calculate the energy in kilowatt-hours. |
Kettle
A 2000Watt kettle may be used for 30 minutes a day. Calculate the energy in kilowatt-hours. |
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| Television
A 250Watt television is left on for 3 hours each day. Calculate the energy in kilowatt-hours. |
Refrigerator
A 200Watt refrigerator is on for 24 hours each day. Calculate the energy in kilowatt-hours. |
Oven
A 2500Watt oven is used for 45 minutes each day. Calculate the energy in kilowatt-hours. |
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