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GCSE Physics double award notes
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Electricity at HomeGCSE Physics pg 134
Aims of the lesson
• Recall how to construct a circuit with multiple switches controlling an electrical device
Two-way switch
Leads
Bulb
Battery
Draw the circuit into your note book-
Aims of the lesson
• Understand how a financial bill for electrical energy is calculatedelectrical energy is calculated for a home
• State the unitunit for domestic electrical energy
• Solve simple problemssimple problems related to domestic electricity
Paying for Electricity• Under the stairs you will find…
kWh = kiloWatt Hour
29581 Units used
The Electric MeterThe Electric Meter
Paying for ElectricityAt my house 29 851 kiloWatt hour units
of electricity have been used
1 kWh
1 000
Joule per second
3 600 seconds
1 kWh = 3 600 000 Joules
29 851 kWh = 107 463 600 000 Joules
Paying for Electricity (pg 140)• The electrical energy we use at home is
measured in kiloWatt hours (kWh)(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…
Finding out how much you owe…
5 4 9 6 8
2 0 5 4 8
10 / 7 / 2009
25 / 8 / 2009
120 Watts
40 Watts
40 Watts
On for 2 ½ hours
Electrical UnitsThe 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)
Paying for ElectricityThe price of the electricity is then
worked out using-
Pg 142- Questions 41, 42 and 43
Total cost = Number of units used x Cost per Unit
Set by the Government
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
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
Earth
Live
Neutral
Earth Wire
Connecting block
Fuse
Live Wire
Neutral Wire
Cable Grip
Insulation
Screw
Fuse holder
Pg 138- Wiring a Three Pin Plug
Electrical Safety• It’s not big and it’s not clever…
based on actual events…
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.
Which Fuse to Use?• Selecting the correct fusePage 139The 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 = I x V460 = I x 230I = 460 / 230
I = 2 A
P I V to the rescue!
Use a fuse just above 2 A, possibly
a 3 A fuse
Question Time• Page 142
Attempt questions 39 and 40
Aims of the lesson
• Recall some of the safety features of electricity in the home
• State the difference between AC and DC electricity
An electrical fault (1)
An electrical fault (2)
Earth wire
Electricity at Homehttp://www.absorblearning.com/media/item.action?quick=73#
Electricity at Home
Direct current (d.c.)
Alternating current (a.c.)