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JEE Main 20146 April
Exam
JEE Main
Year
2014
Date
6 April
Subject
Physics
Chapter
Magnetic Properties of Matter

JEE Main 2014 · 6 April · Physics · Magnetic Properties of Matter

The coercivity of a small magnet, where the ferromagnet gets...

The coercivity of a small magnet, where the ferromagnet gets demagnetised is 3×103A/m3 \times {10}^{3}A / m. The current required to be passed in a solenoid of length 10cm10cm and number of turns 100100, so that the magnet gets demagnetised when inside the solenoid is

Options

  1. A30 mA
  2. B60 mA
  3. C3 A
  4. D6 A

Correct answer

C. 3 A

Step-by-step solution

For solenoid, the magnetic field needed to be magnetised the magnet.

B=μ0nIB = {\mu}_{0}nI

where, n=100,l=10cm=10100m=0.1mn = 100, l = 10cm = \dfrac{10}{100}m = 0 . 1m

⇒3×103=1000.1×I⇒ 3 \times {10}^{3} = \dfrac{100}{0 . 1} \times I

⇒I=3A⇒ I = 3A

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