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# Electricity at Home

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GCSE Physics double award notes

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• One thread of steel wool with 2, 1.5 V batteries and crocodile clips – the distance between the clips should only be about half a centimetre Demo this with a larger current and more wool (roughly 6 or 7 volts)
• Fast finishers try pg 146 Q6 a, i) – v)
• If an appliance has a metal case it needs to be earthed. A fault could cause the live wire to touch the metal case. If the appliance is earthed a large current flows down the earth wire and melts the fuse. If the appliance was not earthed there would be a risk of electrocution.
• Display all the labels by spreading them out along the bottom. Back of the book, numbers 1-8 with the correct term to complete the sentences
• Diagram of domestic wiring- http://www.absorblearning.com/media/item.action?quick=73#
• Display all the labels by spreading them out along the bottom. Back of the book again, numbers 1-4 with the correct term to complete the sentences
• Display all the labels by spreading them out along the bottom. Back of the book again, numbers 1-6 with the correct term to complete the sentences
• ### Electricity at Home

1. 1. Electricity at Home GCSE Physics pg 134
2. 2. Aims of the lesson • Recall how to construct a circuit with multiple switches controlling an electrical device
3. 3. Leads Two-way switch Battery Bulb
4. 4. Draw the circuit into your note book-
5. 5. Aims of the lesson • Understand how a financial bill for electrical energy is calculated for a home • State the unit for domestic electrical energy • Solve simple problems related to domestic electricity
6. 6. Paying for Electricity • Under the stairs you will find… The Electric Meter kWh = kiloWatt Hour 29581 Units used
7. 7. Paying for Electricity At my house 29 851 kiloWatt hour units of electricity have been used 1 kWh 1 000 3 600 seconds Joule per second 1 kWh = 3 600 000 Joules 29 851 kWh = 107 463 600 000 Joules
8. 8. Paying for Electricity (pg 140) • The electrical energy we use at home is measured in kiloWatt hours (kWh) • If ten 100 W light bulbs are on for one hour then 1 kWh of energy will be transferred • 1 kWh is referred to as ‘one unit of domestic energy’ What do you get if you sit under a cow? A pat on the head…
9. 9. Finding out how much you owe… 10 / 7 / 2009 25 / 8 / 2009 2 0 5 4 8 5 4 9 6 8 40 Watts 40 Watts 120 Watts On for 2 ½ hours
10. 10. Electrical Units The number of electrical units used is calculated by- The present meter reading minus previous meter reading Or… The power rating of an appliance (in kW) multiplied by the time it is on (in hours)
11. 11. Paying for Electricity The price of the electricity is then worked out using- Total cost = Number of units used x Cost per Unit Pg 142- Questions 41, 42 and 43 Set by the Government
12. 12. Cost of Electricity • When paying for electricity one unit is the same as 1000 Watts of energy being used in one hour. • If a 60 W bulb is on for 4 hours then this is the equivalent of 60 / 1000 x 4 = 0.24 units = 0.24 kWh
13. 13. Aims of the lesson • Recall some of the safety features of electricity in the home • Recognise the three-pin plug • State the function of a fuse • Recall how to select a fuse for an electrical appliance
14. 14. Pg 138- Wiring a Three Pin Plug Live Earth Neutral Connecting block Earth Live Wire Wire Fuse Neutral Wire Fuse holder Screw Cable Grip Insulation
15. 15. Electrical Safety • It’s not big and it’s not clever… based on actual events…
16. 16. It’s for your own protection… • The Fuse Page 138 A fuse that ‘blows’ has broken the circuit because too much current has over-heated and melted the tiny wire within the fuse.
17. 17. Which Fuse to Use? • Selecting the correct fuse Page 139 The Power Rating and Voltage of a device will always be stated. Usually the voltage is 230 V. e.g. For an electrical jigsaw with a power rating of 460 W P=IxV 460 = I x 230 I = 460 / 230 I=2A Use a fuse just above 2 A, possibly P I V to the rescue! a 3 A fuse
18. 18. Question Time • Page 142 Attempt questions 39 and 40
19. 19. Aims of the lesson • Recall some of the safety features of electricity in the home • State the difference between AC and DC electricity
20. 20. An electrical fault (1)
21. 21. An electrical fault (2)
22. 22. Earth wire
23. 23. Electricity at Home http://www.absorblearning.com/media/item.action?quick=73#
24. 24. Electricity at Home
25. 25. Direct current (d.c.)
26. 26. Alternating current (a.c.)