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JEE Main 201815 AprilMorning ShiftOnline
Exam
JEE Main
Year
2018
Date
15 April
Shift
Morning Shift
Mode
Online
Subject
Physics
Chapter
Magnetic Properties of Matter

JEE Main 2018 · 15 April · Morning Shift · Online · Physics · Magnetic Properties of Matter

The B-H curve for a ferromagnet is shown in the figure. The...

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: The B-H curve for a ferromagnet is shown in the figure. The ferromagnet is placed inside a long solenoid with 1000

Options

  1. A2 mA2 \mathrm{~mA}
  2. B1 mA1 \mathrm{~mA}
  3. C40μA40 \mu \mathrm{A}
  4. D20μA20 \mu \mathrm{A}

Correct answer

B. 1 mA1 \mathrm{~mA}

Step-by-step solution

Given Number of turns, n=1000\mathrm{n}=1000 turns /cm=1000×100/ \mathrm{cm}=1000 \times 100 turns /m/ \mathrm{m} Coercivity of ferromagnet, H=100 A/m\mathrm{H}=100 \mathrm{~A} / \mathrm{m} Current to demagnetise the ferromagnet, I=?\mathrm{I}=? Using, H=nI\mathrm{H}=\mathrm{nI} or, 100=105×I\quad 100=10^5 \times \mathrm{I} ∴\therefore \quad\mathrm{I}=100105=1 mA=\frac{100}{10^5}=1 \mathrm{~mA}
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