Q 12-05-073JEE MainJEE Main 2019 (9 Jan, Shift 1)Easy
A bar magnet is demagnetized by inserting it inside a solenoid of length $0.2\ \text{m}$, 100 turns, and carrying a current of $5.2\ \text{A}$. The coercivity of the bar magnet is
Answer: (B) $2600\ \text{A/m}$
Coercivity is the magnetising field intensity needed to demagnetise the magnet, which here is the $H$ of the solenoid:
$$H = nI = \frac{100}{0.2}\times5.2 = 2600\ \text{A/m}$$
Solution by Sreeraj P, M.Sc Physics