In previous problem, if the current is I and the magnetic field at D has magnitude B, then

Options

A. `B=(mu_0I)/(2sqrt2pi)`
B. `B=(mu_0I)/(2sqrt3pi)`
C. B is parallel to the z-axis
D. B makes an angle of `45^@` with the x-y plane

Answer

(a,d)

Explanation

The magnitude of the magnetic field depends only on the distance
from the x-axis. Point A and C are at distance of 1 unit each
from the x-axis. Points B and D are at distance of `sqrt2` unit each
from the x-axis. Magnetic field at point D,
`B=(mu_0I)/(1sqrt2pi)`
It is obvious that B is inclined at an angle of `45^@` with the
x-y plane.