A bar magnet has a coercivity `8xx10^(3)A//m`. It is desired to damagnetise it by inseting it inside a slenoid 6 cm long and having 60 turns. The current carreid by the solenoid should be

Options

A. `8A`
B. `6A`
C. `4.5A`
D. `2A`

Answer

A

Explanation

The reversed magnetic field needed to damagnetise the specimen is known as coercivity of the material
`B=mu_(0)H`
or `mu_(0)ni=mu_(0)H`
or `(Ni)/(L)=H" "(becausen=(N)/(L))`
or `i=(HL)/(N)`
Given, `H=8xx10^(3)A//m`
L=6cm`=6xx10^(-2)m,and N=60`
turns.
Substituting the values, we get
`i=(8xx10^(3)xx6xx10^(-2))/(60)=8A`