A cylindrical conductor of radius `R` is carrying constant current. The plot of the magnitude of the magnetic field, `B` with the distance, `d` from the centre of the conductor , is correctly represented by the figure:

Options

A.
B.
C.
D.

Answer

d

Explanation

For a point inside the cylinder `(r lt R)` magnetic field is given by `B = (mu_(0) Ir)/(2 pi R^(2))` hence it changes linearly from zero to a maximum value at the surface like in option (a) and (b) . For a point outside the cylinder `(r gt R)` magnetic field is given by `B = (mu_(0)I)/(2 pi r)` hence it is inversely proportional to the distance from the center as shown in option (d) , hence option (d) is correct.