The magnetic field strangth at a distance d from the centre, on the axial line of a very short bar magnet of magnetic moment M, is B. The magnetic induction at a distance 2 d from centre, on equatoroal line of magnet of magnetic moment 8M, will be'

Options

A. 4B
B. `B/2`
C. 2B
D. `B/4`

Answer

B

Explanation

In axial position, `B=(mu_(0))/(4pi)(2M)/(d^(2))`
`(B)/(B^(1))=(M)/(M_(1))xx((d_(2))^(3))/((d_(1))^(3))``implies (B)/(B_(1))=(2M)/(8M)xx((2d)^(3))/d^(3)`
`implies(B)/(B^(1))=2`
`therefore B^(1)=(B)/(2)`