Question

The coercivity of a small magnet where the ferromagnet gets demagnetized is $3\times {10}^{3}A{m}^{-1}$ . The current required to be passed in a solenoid of length 10 cm and number of turns 100, so that the magnet get demagnetized when inside the solenoid, is :

• A. 6A
• B. 30 mA
• C. 60 mA
• D. 3A

Answer 1

The correct option is D 3A

For a solenoid, $H=\frac{Ni}{l}$
Given : H = $3\times {10}^{3}A{m}^{-1}$, N = 100, l = 0.1 m.
Placing these in the given formula, we get current as 3 A.