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Question:

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

285A/m

1200A/m

5200A/jm

2600A/m

Solution:

Coercivity=H=B/μ₀=ni=N*I/l = 100 * 5.2 / 0.2 = 2600A/m