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The coercivity of a certain permanent ma...

The coercivity of a certain permanent magnet is `4.0xx10^(4)Am^(-1)`. The magnet is placed insider a solenoid 20cm long having 700 turns and a current is passed in the solenoid to demagnetise it completely. Find the current

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The correct Answer is:
10
Ae coercivity
`H_(C ) = nI , I = (H_(C )) /n = (4.0 xx10^(4)A//m)/(4xx10^(3)//m)=10 A `
`("As "n = 600/(0.15 m) = 4xx 10^(3) //m)` .
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