Case: Read the passage and answer the question.
The number of magnetic field lines crossing a surface is called the magnetic flux. An electric current can be induced in a coil by a flux change produced by another coil in its vicinity or by a flux change produced by the same coil. The former is called mutual induction and the latter is called self-induction.
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): When the current in a coil is switched off, an emf is induced in that same coil.
Reason (R): The emf induced in a coil by a change in its own current helps that change.
In the light of the above statements, choose the most appropriate answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (A) is correct but (R) is not correct.
Assertion (A) When the current in a coil is switched off, an emf is induced in that same coil. — True. Switching off the current makes the flux linked with the coil fall to zero. This change of flux induces an emf in the coil itself. This is self-induction, and no second coil is needed for it.
Reason (R) The emf induced in a coil by a change in its own current helps that change. — False. The self-induced emf opposes the change of current. When the current falls, the induced emf tries to keep it flowing, so it acts against the fall. For this reason it is also called the back emf.
NCERT (2026-27):
Self-inductance – “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. …”
Self-inductance – “… Thus, the self-induced emf always opposes any change (increase or decrease) of current in the coil.”