A square coil `ACDE` with its plane vertically is released from rest in a horizontal uniform magnetic field `vec(B)` of length `2L` . The acceleration of the coilis

Options

A. less than `g` for all the time till the loop crosses the magnetic field completely
B. less than `g` when it enters the field and greater than `g` when it comes out of the field
C. `g` all the time
D. less than `g` when it enters and comes out of the field but equal to `g` when it is within the field

Answer

D

Explanation

When the coil is within the field, there is no change in magnetic flux passing through it. Thus no current will be induced and the acceleration will be `g`. But according to Lenz's law, the induced current will opposes its motion when it enters or leaves the field. therefore, acceleration will be less than `g`.