electricity at home
DESCRIPTION
GCSE Physics double award notesTRANSCRIPT
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Electricity at HomeGCSE Physics pg 134
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Aims of the lesson
• Recall how to construct a circuit with multiple switches controlling an electrical device
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Two-way switch
Leads
Bulb
Battery
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Draw the circuit into your note book-
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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
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Paying for Electricity• Under the stairs you will find…
kWh = kiloWatt Hour
29581 Units used
The Electric MeterThe Electric Meter
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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
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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…
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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
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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)
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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
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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
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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
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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
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Electrical Safety• It’s not big and it’s not clever…
based on actual events…
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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.
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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
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Question Time• Page 142
Attempt questions 39 and 40
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Aims of the lesson
• Recall some of the safety features of electricity in the home
• State the difference between AC and DC electricity
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An electrical fault (1)
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An electrical fault (2)
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Earth wire
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Electricity at Homehttp://www.absorblearning.com/media/item.action?quick=73#
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Electricity at Home
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Direct current (d.c.)
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Alternating current (a.c.)