JEE Main 27-Aug-2021 Shift 1 Solved Paper

Given, radius of loop is R and velocity of the bar magnet is v.
According to Faraday’s law of electromagnetic induction, the emf induced in loop is given by
e=−

Nd‌ϕ

dt

...(i)
As initially the bar magnet is moving towards the coil, so the rate of change of magnetic flux linked with the coil will increase. Thus, initially the emf induced in coil will decrease as per Eq. (i) (due to –ve sign).
When magnet reaches the middle point in the coil, for that moment the emf induced will be equal to zero because in this situation, change in magnetic flux associated with bar magnet becomes zero.
Now, after that when magnet moves forward, the magnetic flux again starts changing but the polarity of magnetic flux change will be reversed. So, the emf will now increase in opposite direction.
The graph for change in emf of coil is shown below.