The B - H curve for a ferromagnet is shown in the figure. The ferromagnet is placed inside a long solenoid…

The B-H curve for a ferromagnet is shown in the figure. The ferromagnet is placed inside a long solenoid with 1000 turns cm-1. The current that should be passed in the solenoid to demagnetize the ferromagnet completely is, 

  1. 2 mA
  2. 20 μA
  3. 1 mA
  4. 40 μA

Solution

The coercivity of ferromagnet, H=100 A m-1, n×I=100
⇒I=100105=1 mA.

Asked in: JEE Main 2018 (15 Apr)

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