Question

Transformers are used

(a) in DC circuits only
(b) in AC circuits only
(c) in both DC and AC circuits
(d) neither in DC nor in AC circuits

Answer 1

(b) in AC circuits only

When a DC supply is provided to a transformer, there will be no change in flux with time across the coils of the transformer. So, there will be no induced emf in the secondary coil due to changing current in the primary coil. Hence, the transformer cannot operate in DC because of the violation of its working principle.