Do transformers work with alternating or direct electrical supplies?

Transformers only work with alternating electrical supplies (i.e. alternating voltage/current). 

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What do transformers do?

Transformers change the voltage and current of an alternating current. 

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What does a step-down transformer do?

A step-down transformer decreases the voltage and increases the current

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Where could a step-down transformer be used?

A step-down transformer could be used before electricity enters a home, to ensure the voltage is low enough to be safe.

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What does a step-up transformer do?

A step-up transformer increases the voltage and decreases the current.

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Where could a step-up transformer be used?

A step-up transformer could be used as electricity leaves a power station and enters the national grid.

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Why is it important to use step-up transformers before electricity is transmitted across the national grid?

It is important to have a very high voltage and low current to minimise energy loss during transmission.


(a high current would heat the wire causing energy loss via heat)

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How do transformers work?

  1. When supplied with an alternating current, the primary coil will generate an alternating magnetic field.
  2. This then induces an alternating magnetic field in the iron core.
  3. This, in turn, induces an alternating voltage in the secondary coil, which - if the circuit is complete - will lead to an alternating current.

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