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Connect the appliance to the power rating using an arrow!. Appliance . Power rating (W). Were you correct?. How much does electricity cost ?. electrical energy used = power x time. Kilowatt Hours (kWh). A 100W light bulb on for 1 hour will use 100 Watt hours ( Wh ) of electricity
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Connect the appliance to the power rating using an arrow! Appliance Power rating (W)
How much does electricity cost ?
electrical energy used =power x time 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, 1 unit of electricity = 1 kilowatt hour
Drill 5kW on for 2 hours! 1kW costs 10p For example 1. Energy used = Power x time 2. Total cost= number of kilowatt hoursx 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
Kettle 2000W device = 2kW left on for one hour
Hair dryer 1.5kW device left on for half an hour hour
TV 500W device left on for three hours
Light bulb 100W device left on for six hour
Phone charger 1kW device left on for five hours
Questions • Is it cheaper to have your kettle on for one hour a day or your light on for 6 hours? • Which device has the highest power rating? • What two things affect the amount of electricity a device uses? • How many watts are in one kilowatt?
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 A NORMAL BULB COSTS £1 AN ECO BULB COSTS £4
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?
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
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