The coercivity of a bar magnet is $140 Am^{-1}$. To demagnetize it, it is placed inside a solenoid of length 1.6 m and number of turns 112. What is the current flowing through the solenoid?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 2 A
The magnetic field strength H inside a solenoid is,
$H=\frac{N}{l}I$
$⇒H_{coercive}=\frac{N}{l}I$
$⇒140=\frac{112}{1.6}I$
$⇒I=\frac{140}{70}=2A$