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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. 2600 A/m
2. 1200 A/m
3. 520 A/m
4. 285 A/m

Correct answer: 2600 A/m

Solution

Coercivity equals the demagnetizing field H = n*I = (N/L)*I = (100/0.2)*5.2 = 500*5.2 = 2600 A/m.

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