A square coil `ACDE` with its plane vertically is released from rest in a horizontal uniform magnetic field `vec(B)` of length `2L` . The accelaration 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. equal to g all the time
D. less than g when it enters and comes out of the field but equal to pwhen it is within the field

Answer

D

Explanation

There will be three situations,
(i) When the coil is entering into the field, flux increases and from Lenz.s law the induced emf or current opposes the change. Therefore `a lt g`.
(ii) When the coil is completely within the field, flux remains constant and hence no emf is induced. Therefore a = g .
(iii) When the coil is coming out from the field, flux decreases and from Lenz.s law the induced emf or current opposes the change. Therefore `a lt g`.