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Published byAlison Knight Modified over 6 years ago

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Connect the appliance to the power rating using an arrow! Appliance Kettle Iron Television Hair dryer Power rating (W) 1100W 65W 1800W 2000W

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AppliancePower Rating Kettle2000 W Iron 1100 W Television65 W Hairdryer1800 W Were you correct?

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Kilowatt Hours (kWh) A 100W light bulb on for 1 hour will use 100 Watt hours (Wh) of electricity This is usually measured in Kilowatt Hours (kWh) 0.1 kWh On an electricity bill, electrical energy used = power x time 1 unit of electricity = 1 kilowatt hour

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For example Drill 5kW on for 2 hours! 1kW costs 10p 1. Energy used = Power x time 2. Total cost= number of kilowatt hours x cost per kilowatt hour Energy used = 5kW x 2hours Energy used (kWh) = 10kWh Each kWh cost 10p so total is 10p x 10kWhr = £1.00

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Kettle 2000W device = 2kW left on for one hour

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Hair dryer 1.5kW device left on for half an hour hour

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TV 500W device left on for three hours

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Light bulb 100W device left on for six hour

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Phone charger 1kW device left on for five hours

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How much does my electricity cost? DevicePower in watts (W) Power in kilowatt (kW) Time used (hours) Number of units used Total cost Kettle200021Energy = Power x time Energy = 2 x 1 = 2kwh 2 x 10p = 20p Drill500052Energy = 5 x 2 = 1010 x 10p = £1.00 Phone charger Normal Light bulb TV Hairdryer

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Answers DevicePower in watts (W) Power in kilowatt (kW) Time used (hours) Number of units used Total cost Kettle200021Energy = Power x time Energy = 2 x 1 = 2kwh 2 x 10p = 20p Phone charger 1000w1kW5Energy = 1 x 5 = 55 x 10p = 50p Light bulb100W0.1kW6Energy = 0.1x 6 = 0.60.6 x 10p = 6p TV500W0.53Energy = 0.5 x 3= 1.51.5 x 10p = 15 p Hairdryer15001.5kW0.5Energy = 1.5 x 0.5 = 0.75 0.75 x 10p = 7.5p

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Questions 1.Is it cheaper to have your kettle on for one hour a day or your light on for 6 hours? 2.Which device has the highest power rating? 3.What two things affect the amount of electricity a device uses? 4.How many watts are in one kilowatt?

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Eco versus normal? To run a normal 100W light bulb for 5 hours a day all year costs: 100W x 5hours = 500Wh = 0.5kWh 0.5kWh x 12p = 6p 6p x 365 days = 2190p = £21.90 To run a 15W eco bulb for 5 hours a day all year costs: 15W x 5hours = 75Wh = 0.075kWh 0.075kWh x 12p = 0.9p 0.9p x 365 days = 328.5p = £3.29

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Electricity Meters

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How do we know how much electricity we use? We have meter readings that record what we use. We get charged either each month or 3 month period How many units of electricity had been used by this family? 2113 2832

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Copy and complete Power is measured in _________ (W) The name for 1000watts is a_________(kW) How much electrical energy is transferred depends on; - How ________an appliance is switched on for - How ________the appliance transfers energy (its power rating) Keywords; long; watts; kilowatts; fast

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HW - Is charging my phone expensive? Find out: What power your phone is How long it takes to charge The cost if it is 10p a unit

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