A coil is placed in a magnetic field as shown below : B A current is induced in the coil because B is:
(A)Outward and decreasing with time✓ Correct
(B)Parallel to the plane of coil and decreasing with time
(C)Parallel to the plane of coil and increasing with time
(D)Outward and increasing with time
Answer: (A)
Solution
A current is induced only when the flux through the coil changes, so the field must be perpendicular to the plane of the coil, that is, directed out of the plane. The induced current shown is anticlockwise, and by the right-hand rule an anticlockwise current produces a field pointing out of the plane inside the coil. By Lenz's law this induced field opposes the change, reinforcing the existing outward flux, which means that outward flux is decreasing. The field is outward and decreasing with time.
JEE Main · 2021 · 31 Aug 2021 · Shift 2 · Single correct option
