1. Sustainable Energy Lesson 5

2. Learning objective: To explain the link between the power rating and energy use of an electrical appliance. Must: Recall the definition for power and give its unit of measurement – Grade D Should: Be able to calculate power rating and energy used by an electrical appliance. - Grade C Could: Calculate the power of a range of appliances using an ammeter and a voltmeter – Grade B. Keywords: Power, current, voltage, watt and energy transfer.

3. Starter-Label the power station

4. How many did you get? 1. Furnace and boiler. 2. Turbine. 3. Generator. 4. Transformer.

5. Mains supply. What is the mains supply voltage to our homes? 230 V (volts). You need to remember this.

6. Do different appliances use different amounts of electricity?

7. Joules Energy is measured in Joules (J) We need to know how much energy something uses over time = a rate We can use Joules per second (J/s) 1 Joule / sec = 1 Watt (W) A 100W light bulb uses 100J of energy every second

8. Power When an electric current is passed through a device electric current is transferred from the supply to the device. The rate at which this energy is transferred is called POWER. Power is measured in WATTS (W).

9. Power Rating Different electrical devices have different power ratings They use different amounts of electrical energy over a given time. 15W 100W VS

10. P = I x V Power (Watts) = Current (amps) x Voltage (volts) Voltage = Potential Difference

11. Pee on the Ivy P = I x V

12. Task- Complete the table using the equation P=IV AppliancePower (w)Voltage (v)Current (A) Kettle300013.0 Toaster1550230 Microwave1300240 Drill2401.5 Door Lift230010 Fax Machine2301.0 CD player150.06 TV59230 Vacuum Cleaner2402.7 Hairdryer8003.5 Desk Lamp124.2 Sewing Machine2300.17 Possible homework task

13. Task- Complete the table using the equation P=IV AppliancePower (w)Voltage (v)Current (A) Kettle300023013.0 Toaster15502306.7 Microwave13002405.4 Drill3602401.5 Door Lift230023010 Fax Machine230 1.0 CD player152500.06 TV592300.26 Vacuum Cleaner6482402.7 Hairdryer8002293.5 Desk Lamp50124.2 Sewing Machine392300.17

14. The Watt 1 Watt = 1 Joule transferred in 1 second Power (W)= Energy (J) / Time (s)

15. DevicePower Rating (Watt) Time (sec)Energy (J) Kettle 2400 180 Energy = Power x Time Energy = 2400W x (180s) Energy = 432000J 432000

16. Electric Cooker: 10kW Fridge: 50W Freezer: 300W Washing machine: 500W Dishwasher: 1300W

17. Electric Cooker: 10kW. 45mins Fridge: 50W. 24hours Freezer: 300W. 24hours Washing machine: 500W. 1 hour Dishwasher: 1300W. 45mins

18. DevicePower Rating (Watt) Time (sec)Energy (J) Electric Cooker 10000270027000000 Fridge50864004320000 Freezer3008640025920000 Washing Machine 50036001800000 Dishwasher130027003510000

19. Total energy use in one day: 63036000J or 63 million and 36 thousand Joules and Total Energy for 3 months: 5673240000J or 5 billion, 6 hundred and seventy three million, 2 hundred and forty thousand Joules!

20. Plenary- True or False 1.Power is measured in watts? 2.Power= voltage / current? 3.Current is measured in volts? 4.Voltage is measured in volts? 5.Potential difference is another word for voltage? 6.I is the symbol for current? 7.The mains supply voltage to our homes is 240V? 8.The higher the power rating the more energy is used? 9.10 watts means 10 joules of energy every minute?