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

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

4. 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

5. 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

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

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

8. TV 500W device left on for three hours

9. Light bulb 100W device left on for six hour

10. Phone charger 1kW device left on for five hours

11. 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

12. 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

13. 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?

14. 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

15. Electricity Meters

16. 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

17. 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

18. 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