Q 12-06-104JEE MainJEE Main 2021 (31 Aug, Shift 2)Easy
A coil is placed in a magnetic field $\vec B$ as shown below:
A current is induced in the coil because $\vec B$ is:
Answer: (C) outward and decreasing with time
A field parallel to the plane gives no flux, so options (1) and (4) cannot induce a current.
The induced current is anticlockwise, which produces a field out of the page at the centre. By Lenz's law it opposes the change, so the outward flux must be decreasing.
Hence $\vec B$ is outward and decreasing with time.
Solution by Sreeraj P, M.Sc Physics