Question

An E.M.F. can be induced by _________

(a) Change in the magnetic field only

(b) Change in the area of cross section only

(c) Change in angle between magnetic field and area only

(d) Change in the magnetic field, area or angle between them

I had been asked this question in semester exam.

This intriguing question comes from Electromagnetic Induction in section Electromagnetism of Basic Electrical Engineering

Answer 1

The correct option is (d) Change in the magnetic field, area or angle between them

Explanation: emf=-dϕ/dt. We know ϕ flux is the dot product of magnetic field vector and area vector.

ϕ=BAcos(θ), hence if either of the three, that is, magnetic field, area or angle changes, the emf will change, flux changes due to which emf can be induced.