The coercive force for a certain permanent magnet is 4.0 x 104A/m. This magnet is placed inside a long solenoid of 40turns/cm and a current is passed in the solenoid to demagnetise it completely. Find the current.

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1 Answers

B = μ0ni,  H = B/μ0

Given n = 40turn/cm = 4000turns/m

=> H = ni

H = 4 × 104A/m

=> i = H/n = (4 x 104)/4000 = 10A.

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