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JEE Main201815 Apr 2018Morning ShiftPhysicsMagnetic Properties of MatterActual

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

Options

  1. A2 ~mA
  2. B1 ~mA
  3. C40 A
  4. D20 A

Correct answer

B. 1 ~mA

Step-by-step solution

Given Number of turns, n =1000 turns / cm =1000 100 turns / m Coercivity of ferromagnet, H =100 ~A / m Current to demagnetise the ferromagnet, I =? Using, H = nI or, 100=10^5 I I = 100 10^5 =1 ~mA

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