Question

You are told that a particular device takes alternating current at one voltage and converts it to a different voltage. What device is it?

Answer 1

This device is a transformer.

A transformer is made of two coils. An alternating current in the first coil produces a varying magnetic field and so a varying magnetic flux through the second coil. The varying magnetic flux creates an electromotive force in the second coil, for the Faraday's law of induction, that is proportional to the variation of the flux, and this electromotive force corresponds to the new voltage on the second coil.

The relationship between the voltage in the first coil (Vp) and the voltage in the second coil (Vs) is given by

`(V_p)/(V_s)= (N_p)/(N_s)`
where Np and Ns are the number of turns in the primary and secondary coil, respectively.