Question

The transformer works on
a) AC only
b) DC only
c) Both AC and DC
d) AC more efficiently than DC

Answer 1

Hint: A transformer works on the principle of mutual induction. Mutual is the process where two coils are placed close to each other such that the changing magnetic field of one ( i.e. primary) due to the changing current gets linked to the other(i.e. secondary), then emf is induced in the second coil. From this principle, we can compare both the AC and DC and analyze whether they satisfy the criteria for mutual induction.

Complete step-by-step solution:

The above figure represents a transformer wherein the primary and the secondary coils are mutually inducted. The emf is induced in a secondary coil only if there is a changing magnetic field generated by the primary coil. The field produced by a primary coil is given by i.e. $B={\mu }_{\circ }ni$ where ${\mu }_{\circ }$ is the permeability constant, n is the number of turns in the primary and i is the current through it. The field generated can induce emf in the secondary coil if and only if the current through it keeps on changing at any given instant of time. In a DC source, the current remains constant but in an AC source the current keeps on changing. Hence a transformer will only work on AC.
Hence the correct answer is option (a).

Note: There are two types of transformers. One is a step-up transformer and the other is a step-down transformer. In the step-up transformer the voltage across the primary is less than that of the secondary coil whereas for a step-down transformer the voltage across the primary is more than that of the secondary.