Question

Draw a labelled diagram of a step-up transformer. Obtain the ratio of secondary to primary voltage in terms of number of turns and currents in the two coils.

Answer 1

Step-up transformer.

Any one of the following

Let ϕ be the flux in each turn in the core at a time/due to the current in the primary when a voltage Vp is applied to it.

Then the induced emf or voltage Es in the secondary with N

*, turns is

Vs = Es = Ns dϕ/dt

The alternating flux ϕ also induces an emf, called back emf in the primary given by