| The B-H curve for a Ferro magnet is shown in the figure. The Ferro magnet is placed inside a ling solenoid with 1000 turns/cm. The current that should be passed in the solenoid to demagnetise the Ferro magnet completely is: |
| [JEE Online 15-04-2018] |
 |
A) \[2mA\]
B) \[1mA\]
C) \[40\mu A\]
D) \[20\mu A\]
Correct Answer: B
Solution :
| [b] \[N=1000\,\,turns/an\] |
| \[H=\frac{Nl}{l}\] |
| \[100\frac{A}{M}=\frac{1000\times l}{{{10}^{-2}}}\] |
| \[100A={{10}^{5}}\times I\] |
| \[{{10}^{-3}}A=I\] |
| \[I=1mA\] |
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