Question

What is the core of the transformer made up of?
A. gold
B. soft iron
C. aluminium
D. copper

Answer 1

Hint: The primary and the secondary coil are wound up on the core. This is done to avoid magnetic flux from leaking. The core of the transform is decided on the basis of magnetic permeability of the material and economic availability.

Complete step-by-step answer:
Transformer is an electrical device, which can vary the current. It works on the principle of mutual induction, where two coils are coupled, namely the primary and the secondary coil. The primary coil creates a varying magnetic flux, which in turn induces an EMF on the secondary coil.
If the number of windings in the primary coil is greater than the windings in the secondary coil, it is called a step-down transformer. Similarly, if the windings in the secondary coil are greater than the windings in the primary coil, it is called a step-up transformer.

An ideal transformer is a transformer where there is no loss in magnetic flux or no flux leakage due to coupling and the inductance due to the winding of the coils is zero.
In reality, the winding of the coil has some impedance and there is magnetic flux leakage. To avoid leakage of flux the coils are wound on a highly permeable magnetic core.
In the given options, soft iron is used as the core of the transformer as it has high magnetic permeability, easy availability and is cost effective.

Note: The efficiency of the transformer depends on how well the input power is transferred as output power. Thus to increase the efficiency of the transformer, the windings of the coil must be increased and/or magnetic flux leakage must be reduced.