Question

The coercivity of a small bar magnet is $4\times {10}^{3}A/m$. It is inserted inside a solenoid of $500$ turns and length $1m$ to demagnetise it. The amount of current to be passed through the solenoid will be :

• A. $2.5A$
• B. $5A$
• C. $8A$
• D. $10A$

Answer 1

The correct option is C $8A$

$H=ni\Rightarrow i=\frac{H}{n}=\frac{4\times {10}^3}{500}=8A$