This document discusses electricity in the home, including: - How to construct simple circuits with switches controlling electrical devices and drawing circuit diagrams. - How domestic electricity usage is measured in kilowatt-hours (kWh) and how electrical bills are calculated based on the meter reading and cost per kWh. - Electrical safety features like three-pin plugs with fuses that break circuits if too much current overheats the fuse wire, and selecting the correct fuse rating based on an appliance's power and voltage. - The difference between alternating current (AC) and direct current (DC) electricity supplied to homes.

1. Electricity at Home
GCSE Physics pg 134

2. Aims of the lesson
• Recall how to construct a circuit with
multiple switches controlling an
electrical device

3. Leads
Two-way switch
Battery
Bulb

4. Draw the circuit into your note book-

6. 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

7. Paying for Electricity
• Under the stairs you will find…
The Electric Meter
kWh = kiloWatt
Hour
29581 Units used

8. 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

9. 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…

10. 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

11. 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)

12. 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

13. 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

14. 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

15. 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

16. Electrical Safety
• It’s not big and it’s not clever…
based on actual events…

17. 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.

18. 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

19. Question Time
• Page 142
Attempt questions 39 and 40

20. Aims of the lesson
• Recall some of the safety features of
electricity in the home
• State the difference between AC and
DC electricity

21. An electrical fault (1)

22. An electrical fault (2)

23. Earth wire

24. Electricity at Home
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25. Electricity at Home

26. Direct current (d.c.)

27. Alternating current (a.c.)