The coercivity of a bar magnet is `120A//m`. It is to be demagnetised by placing it inside a solenoid of length `120cm` and number of turns 72. The current (in A) flowing through the solenoid is:

Answer

`(2)`

Explanation

As is clear from figure.
coercivity `OA=H=ni=120A//m`.
Here, n=number of turns/length `=(72)/(1*2(m))=60`.
`:. i=H/n=(120)/(60)=2A`