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Slide 1

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Mains Electricity
Electricity Topic 3…read more

Slide 2

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Mains Electricity
· In the United Kingdom that mains
electrical supply is about 230 volts.
· The supply is an alternating current
(AC) which means that the direction
of the current is constantly changing.
· The supply has a frequency of 50
hertz.…read more

Slide 3

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The Plug
· The case is made from tough
plastic or rubber, because these
materials are good electrical
· The three pins are made from
brass, which is a good conductor
of electricity.
· There is a fuse between the live
terminal and the live pin.
· The fuse breaks the circuit if too
much current flows.
· The cable is secured in the plug
by a cable grip. This should grip
the cable itself, and not the
individual wires inside it.…read more

Slide 4

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· Many electrical appliances have metal cases, including
cookers, washing machines and refrigerators. The
earth wire creates a safe route for the current to flow
through if the live wire touches the casing.
· You will get an electric shock if the live wire inside an
appliance, such as a cooker, comes loose and touches
the metal casing. However, the earth terminal is
connected to the metal casing so that the current goes
through the earth wire instead of causing an electric
shock. A strong current surges through the earth wire
because it has a very low resistance. This breaks the
fuse and disconnects the appliance.…read more

Slide 5

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Important Equations
Charge, current and time
Electrical charge is measured in coulomb, C. The amount of electrical charge
that moves in a circuit depends on the current flow and how long it flows for.
The equation below shows the relationship between charge, current and time:
· charge (coulomb, C) = current (ampere, A) × time (second, s)
Energy transferred, potential difference and charge
For a given amount of electrical charge that moves, the amount of energy
transformed increases as the potential difference (voltage) increases.
The equation below shows the relationship between energy transformed,
potential difference and charge:
· energy transformed (joule, J) = potential difference (volt, V) × charge
(coulomb, C)…read more

Slide 6

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Important Equations
To help find
what fuse to
use Total
Voltage Current Current Time
(V) (I) (I) (t)
(V)…read more


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