Question

A bar magnet is demagnetised by inserting it inside a solenoid of length $0.2\text{m}$ , having $100$ turns and carrying a current of $5\text{A}$. The coercivity of the bar magnet is

• A. $1500{\text{Am}}^{-1}$
• B. $1200{\text{Am}}^{-1}$
• C. $2500{\text{Am}}^{-1}$
• D. $2300{\text{Am}}^{-1}$

Answer 1

The correct option is C $2500{\text{Am}}^{-1}$

Coercivity $,H=\frac{B}{{\mu }_0}=ni[\because n=\frac{N}{l}]$

$H=\frac{N}{l}i$

$\therefore H=\frac{100}{0.2}\times 5$

$\Rightarrow H=2500{\text{Am}}^{-1}$

Hence, option (c) is the correct answer.