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Slide 1

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The National Grid
Electricity reaches our homes from power stations through the
National Grid:
Step up Step down
Power station Homes
transformer transformer
If electricity companies transmitted electricity at 240 volts through
overhead power lines there would be too much ______ loss by the time
electricity reaches our homes. This is because the current is ___. To
overcome this they use devices called transformers to "step up" the
voltage onto the power lines. They then "____ ____" the voltage at the
end of the power lines before it reaches our homes. This way the
voltage is _____ and the current and power loss are both ____.
Words ­ step down, high, power, low, high…read more

Slide 2

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Transformers
Transformers are used to _____ __ or step down
_______. They only work on AC because an ________
current in the primary coil causes a constantly alternating
_______ ______. This will "_____" an alternating
current in the secondary coil.
Words ­ alternating, magnetic field, induce, step up, voltage
We can work out how much a transformer will step up or
step down a voltage:
Voltage across primary (Vp) No. of turns on primary (Np)
Voltage across secondary (Vs) No. of turns on secondary (Ns)…read more

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