Draw a labelled diagram of a step up transformer and explain how does it work. State two characteristics of the primary coil as compared to it's secondary coil.

Labelled diagram of a step up transformer is given below:

The transformer used to change a low alternating voltage to a high alternating voltage (of same frequency) is called a step up transformer (i.e. E_s > E_p).

When the terminals of primary coil are connected to the source of alternating e.m.f. a varying current flows through the primary coil. This varying current produces a varying magnetic field in the core of the transformer.Thus the magnetic flux linked with the secondary coil vary due to which an e.m.f. is induced in it. The induced e.m.f. varies in the same manner as the applied e.m.f. in the primary coil varies and thus the induced e.m.f. has the same frequency as that of the applied e.m.f.

In a step up transformer the number of turns in the secondary coil is more than the number of turns in the primary coil ( N_s > N_p) i.e., turns ratio n > 1 as shown above.

Since current in primary coil is more than in the secondary coil (or I_p > I_s), so the wire in the primary coil is kept thicker than in the secondary coil.

Two characteristics of the primary coil as compared to it's secondary coil are —

1. The number of turns in the primary coil are less than that of the secondary coil.
2. The wire of the primary coil is thicker than that of the secondary coil.