The battery charger for an mp3 player contains a step-down transformer with a turns ratio of 1: 29, so that the voltage of 120 v available at a wall socket can be used to charge the battery pack or operate the player. what voltage does the secondary coil of the transformer provide?

Transformer contains two coils: primary and secondary. They allow change of voltage to lower or higher value. In first case we have step-down and in second case we have step-up transformer.

Formula used for transformer is:


Where:
N1 = number of turns on primary coil
N2 = number of turns on secondary coil
V1 = voltage on primary coil
V2 = voltage on secondary coil

In a step-down transformer primary coil has more turns than secondary coil. So the ratio 1:29 means that for each turn on secondary coil we have 29 turns on primary coil.

We can solve the equation for V2:


Secondary coil provides voltage of 4.14V.