The working of a transformer is based on the principle of
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Mutual Induction
A transformer has two coils wound on a common iron core. An alternating current in the primary coil produces a changing magnetic flux, which links the secondary coil and induces an emf in it. The emf induced in one coil by a changing current in another is mutual induction.
\( \displaystyle \varepsilon_s = -M\frac{dI_p}{dt} \)
Why the other options are incorrect
Option (2) Self Induction — Incorrect. Self induction also occurs in each coil, but it does not transfer energy from the primary to the secondary.
Option (3) Ampere's Law — Incorrect. Ampere’s law relates a magnetic field to the current producing it; it does not explain the induced emf.
Option (4) Lenz's Law — Incorrect. Lenz’s law gives only the direction of the induced emf, not the working principle.
NCERT (2026-27):
Transformers – “For many purposes, it is necessary to change (or transform) an alternating voltage from one to another of greater or smaller value. This is done with a device called transformer using the principle of mutual induction.”