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Transformer

What is a Transformer?
A transformer is made from two coils, one on each side of a soft iron core.
It can decrease the voltage (called a step down transformer).

or increase the voltage (called a step up transformer, shown below).

Alternating current is passed through the primary coil (the input) which creates a changing magnetic field in the iron core.
The changing magnetic field then induces alternating current of the same frequency in the secondary coil (the output).

A step up transformer has more turns of wire on the secondary coil, which makes a larger induced voltage in the secondary coil.
It is called a step up transformer because the output voltage is larger than the input voltage. If the secondary coil has twice as many turns of wire then the output voltage will be twice the input voltage. See the transformer equation.

Transformer power
If a transformer doesn't waste any energy, then it must give out as much energy every second as put in. In other words: its power output (in watts,W) must be the same as its power input. for this happen, the current as well as the voltage

The Powers input and output
The power input
The power output
= Voltage x Current
Voltage x Current
= 230 x 0.1
= 10 x 2.3
=23 W

=

=23 W

Transformer that doesn’t waste power
Input
Output
Voltage

X

Input
Current

=

Output

X

Voltage

Current

Connection between input and output voltages
Input voltage ÷ Output voltage = Turns on input coil ÷ turns on output
coil