QJEEM14Ph6711: JEE Main 2014 Physics - Class 12 JEEM14Ph6711 Solution: The coercivity of a small magnet where the ferromagnet gets…

Question

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The coercivity of a small magnet where the ferromagnet gets demagnetized is

3 \times 10^{3} A m^{- 1} .

The current required to be passed in a solenoid of length

10

c m

and number of turns

100,

so that the magnet gets demagnetized when inside the solenoid, is :

Accepted Answer

Magnetic field in solenoid

B = μ_{0} n i

\Rightarrow \frac{B}{μ_{0}} = n i

(Where

n =

number of turns per unit length)

\Rightarrow \frac{B}{μ_{0}} = \frac{N i}{L}

\Rightarrow 3 \times 10^{3} = \frac{100 i}{10 \times 10^{- 2}}

\Rightarrow i = 3 A

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