# A bar magnet is demagnetized by inserting it inside a solenoid of length 0.2 m, 100 turns

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A bar magnet is demagnetized by inserting it inside a solenoid of length 0.2 m, 100 turns, and carrying a current of 5.2 A. The coercivity of the bar magnet is :

(1) 1200 A/m

(2) 2600 A/m

(3) 520 A/jm

(4) 285 A/m

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Ans: (2) 2600 A/m

Sol: Coercivity = H = $B\over\mu_0$

= ni = $N\over l$ i = ${100\over0.2}\times5.2$

= 2600 A/m