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Electromagnetism

Transmission of Electricity and Energy Loss.

A generator at a power station might produce electricity
with a voltage of 25,000 V and a current of 8,000 A.

Such a large current would cause the cables of the
National Grid to get hot due to the heating effect of current.
Energy would then be lost as heat to the atmosphere
and by the time that the electricity had traveled from the
power station through the cables to the towns and
factories, much of the original energy would be lost.

To reduce the energy loss, a step up transformer at the
power station is used to raise the voltage to 400,000 V.
This is 16 times the input voltage of 25,000 V.

The power equation tells us
that if the voltage has gone up by 16 times,
then the current must be reduced by 16 times.

The original current of 8,000 A is reduced to
8000 ÷ 16 = 500 A.
This current is still high but the thickness of the cables
means that the heating effect is minimal.

At factories, a step down transformer reduces the
voltage to 33,000 V. For houses, a step
down
transformer reduces the voltage to 230 V.

The electricity produced by power stations is in the form of
alternating current because

1. It is easy to generate alternating current.

2. Transformers will not work with direct current.

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