The current in a coil is varied. What can we say about the emf induced in the same coil?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → An emf can be induced and it is called self-induction.
When the current in a coil changes, the magnetic flux it sets up through its own turns changes. So an emf is induced in the same coil.
Option (1) An emf cannot be induced. — Incorrect. A changing current changes the flux linked with the coil itself, and any change of flux through a coil induces an emf in it.
Option (2) An emf can be induced and it is called mutual induction. — Incorrect. Mutual induction is the emf induced in a neighbouring coil by a changing current in another coil. Here the emf appears in the coil that carries the changing current.
Option (3) An emf can be induced and it is called self-induction. — Correct. An emf induced in a single coil by varying the current through the same coil is called self-induction. This emf opposes the change in the current.
Option (4) An emf can be induced and it is called mutual impedance. — Incorrect. Impedance is the total opposition of an ac circuit to the current, made up of its resistance and reactances. It is not the name of an induction effect.
NCERT (2026-27):
Self-inductance – “In the previous sub-section, we considered the flux in one solenoid due to the current in the other. It is also possible that emf is induced in a single isolated coil due to change of flux through the coil by means of varying the current through the same coil. This phenomenon is called self-induction.”