of electrically powered machines have transformers in them,
but how do they transform the electricity?
transformer changes the voltage of the electricity. It can
only work using AC (alternating current). It transforms
electricity at one voltage into electricity at another voltage.
gadgets need electrical transformers because the mains electricity
comes in at 240 Volts; that's enough to kill you. And what's
more the electronic circuits that most modern machines use
would burn up in an instant if they were connected to electricity
at this voltage.
To do its magic on the high voltage and change it to low
voltage the electrical transformer uses two rather intriguing
and important phenomena. Firstly whenever an electric current
flows, there is magnetism around it. Secondly whenever a
magnetic field changes (by moving or by changing strength)
a voltage is made. If there's a wire close by when this
happens then a current will flow in the wire as the magnetism
The electrical transformer takes in high voltage electricity
and lets it run through lots of coils wound around an iron
core. Because the current is alternating the magnetism in
the core is also alternating. Also round the core is an output
wire with less coils. The changing magnetism generates a current
in the wire and less coils means less voltage. So the voltage
You can do
it all the other way to 'step-up' the voltage with more
coils on the output than on the input. Huge dangerously
high voltages are generated by such step-up electrical transformers
at power stations.
Unfortunately this transformation takes some energy so you
get slightly less energy out of the transformer than you
put in, but the loss is usually only small.
transformer uses an input current to make a changing magnetic
field in an iron core. This changing field is used to generate
a voltage in the output coil. Each turn on the input coil
generates a unit of magnetic field in the iron core and
each turn on the output coil traps a unit of magnetic field.
So, for example, if there are 100 loops on the input coil,
the magnetic field in the core will be 100 times as strong
as if there were only one coil.
lot of 100 loops generates the same voltage. If there are
10 lots of 100 loops stacked end to end, the voltages add
up. The output voltage is 10 times the input voltage. Voila
extra voltage! To make up for the extra voltage, there is
a proportional drop in current