Question

A magnet is moved towards a coil, first quickly and then slowly. The induced e.m.f. produced is :

• A. Larger in first case
• B. Smaller in first case
• C. Equal in both cases
• D. Larger or smaller, depending upon resistance of the coil

Answer 1

The correct option is A Larger in first case

Emf induced in the coil $E=-\frac{d\varphi }{dt}$
where $\varphi$ is the magnetic flux.
Thus emf induced is proportional to rate of change of magnetic flux.
When a magnet is moved towards the coil quickly, rate of change of flux is larger that that if the magnetic is moved slowly, thus larger emf is induced due to quick movement of the coil.