The coercivity of a small magnet where the ferromagnet gets demagnetised is `3xx10^(3)A.m^(-1)` The current required to be passed in a solenoid of length 10cm and number of turns 100 so that the magnet gets demagnetised when inside the solenoid is

Options

A. 6A
B. 30mA
C. 60 mA
D. 3A

Answer

D

Explanation

Given, coercivity `H = 3 xx 10^3 Am^(-1)`
`B = mu H = mu_0 H ( because mu_r = 1)`
` B = mu_0 xx 3 xx 10^3`
From the solenoid `B = mu_0 N/l I = mu_0 3 xx 10^3`
` rArr I = 3A`