how does a transformer work
Answers
A transformer needs an alternating current that will create a changing magnetic field. A changing magnetic field also induces a changing voltage in a coil. This is the basis of how a transformer works:
The primary coil is connected to an AC supply
An alternating current passes through a primary coil wrapped around a soft iron core
The changing current produces a changing magnetic field
This induces an alternating voltage in the secondary coil
This induces an alternating current (AC) in the circuit connected to the secondary coil
It's important to know that:
There is no electrical connection between the primary and the secondary coils.
Transformers only work if AC is supplied to the primary coil. If DC was supplied, there would be no current in the secondary coil.
As the current in the primary coil increases steadily or decreases steadily, there is a constant voltage induced in the secondary coil.
As the voltage in the primary coil reaches maximum strength the voltage induced in the secondary coil is at its weakest (zero volts).
Calculating voltages
The ratio between the voltages in the coils is the same as the ratio of the number of turns in the coils.
Primary voltage / secondary voltage = turns on primary / turns on secondary
This can also be written as:
Vp/Vs = Np/Ns
Step-up transformers have more turns on the secondary coil than they do on the primary coil.
Step-down transformers have fewer turns on the secondary coil than they do on the primary coil.
