Consider the following statements:
(A) An emf can be induced by moving a conductor in a magnetic field.
(B) An emf can be induced by changing the magnetic field
(C) An emf can be induced by changing the electric field
(D) An emf can be induced by moving a conductor in an electric field
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A) and (B) only
By Faraday's law an emf is induced only when the magnetic flux through a circuit changes, or when a conductor cuts magnetic field lines.
(A) An emf can be induced by moving a conductor in a magnetic field. — Correct. The moving conductor cuts field lines and a motional emf \( \varepsilon = B\,l\,v \) appears.
(B) An emf can be induced by changing the magnetic field. — Correct. A changing field changes the flux through a loop, which induces an emf.
(C) An emf can be induced by changing the electric field. — Incorrect. A changing electric field produces a magnetic field (through the displacement current), not an induced emf.
(D) An emf can be induced by moving a conductor in an electric field. — Incorrect. A conductor moving in an electric field cuts no magnetic field lines and the flux does not change, so no emf is induced.
Statements (A) and (B) are correct, which is Option (2).
NCERT (2026-27):
Motional Electromotive Force – “… The induced emf Blv is called motional emf. Thus, we are able to produce induced emf by moving a conductor instead of varying the magnetic field, that is, by changing the magnetic flux enclosed by the circuit.”
Motional Electromotive Force – “… On the other hand, it is not obvious how an emf is induced when a conductor is stationary and the magnetic field is changing – a fact which Faraday verified by numerous experiments.”