Question

Whenever the magnetic flux ($\mathrm{\varphi }$) linked with a coil changes the emf is induced in the circuit, This emf lasts

Answer 1

Induced emf:

1. Whenever a bar magnet is pulled into or out of the coil, some emf has been created. Motion in separate orientations produces EMFs of opposite polarities, and reversing poles reverse the EMFs. The same results are obtained if the coil instead of the magnet is adjusted; it is the relative movement that is significant.
2. As long as the change in magnetic flux continues. This is substantiated by Faraday's laws of electromagnetic induction and the direction of induced current can be found using Lenz’s law.

Mathematically, this can be represented as:

$\mathrm{E}=-\frac{\mathrm{d\varphi }}{\mathrm{dt}}$

Here,

E is the induced emf.

$\mathrm{\varphi }$ is the magnetic flux.

Therefore, emf will last as long as flux keeps changing.