Download Electricity Distribution

Electricity Distribution
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What is a transformer?
The voltage of an alternating current can be changed using
a device called a transformer.
A transformer contains two
coils that are wound around
a soft iron core.
iron core
The alternating current in
the primary (input) coil
produces an alternating
magnetic field.
This alternating magnetic
field induces an alternating
current in the secondary
(output) coil.
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primary
coil
secondary
coil
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How does a transformer change voltage?
The voltage induced in the secondary (output) coil depends
on the number of turns on the primary and secondary coils.
A step-up transformer
has more turns on the
secondary coil and so
increases voltage.
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A step-down transformer
has fewer turns on the
secondary coil and so
decreases voltage.
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Transformer power
Transformers not only change
voltage; they also change current.
If the voltage increases, such as in a
step-up transformer, the current
decreases. This is because for any
transformer:
power in = power out
And because:
power = voltage × current
If the voltage increases, the current must decrease to ensure
that power out remains the same as power in.
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Why use high voltages for distribution?
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Example uses for transformers
Step-up transformers are mainly used in power transmission
to increase voltage to reduce energy loss. Some household
appliances (such as older style CRT TVs) also increase
voltages using step-up transformers.
Step-down transformers
are used in electricity
substations to reduce
the voltage to 230 V for
domestic use.
Appliances generally reduce this again, as most electronic
circuits use 5–12 V.
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Transformers and the supply chain
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The electricity supply chain
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