A bar magnet has coercivity `4xx10^(3) Am^(-1)`. It is desired to demagnetise it by inserting it inside a solenoid `12 cm` long and having `60` turns. The current that should be sent through the solenoid is

Options

A. 2A
B. 4A
C. 6A
D. 8A

Answer

D

Explanation

`n= (N)/(l) = (60)/(0.12) = 500` tum/m
`H= 4 xx 10^(3)A//m`
`therefore i= (H)/(n) = (4 xx 10^(3))/(500)= 8A`