Question

whose principle transformer works?

Answer 1

Hey mate,

Transformer works on the principle of Faraday's law of electromagnetic induction. 

hope this helps you out!

Answer 2

A transformer consists of two electrically isolated coils and operateson Faraday's principal of “mutual induction”, in which an EMF is induced in the transformers secondary coil by the magnetic flux generated by the voltages and currents flowing in the primary coil winding.