Question 107: Magnetism and Matter

Question

The coercivity of a small magnet where the ferromagnet gets demagnetized is $$3 	imes {10^3}\,A{m^{ - 1}}.$$ The current required to be passed in a solenoid of length $$10$$ $$cm$$ and number of turns $$100,$$ so that the magnet gets demagnetized when inside the solenoid, is :

Accepted Answer

Magnetic field in solenoid $$B = {\mu _0}ni$$
$$ \Rightarrow {B \over {{\mu _0}}} = ni$$
(Where $$n=$$ number of turns per unit length)
$$ \Rightarrow {B \over {{\mu _0}}} = {{Ni} \over L}$$
$$ \Rightarrow 3 	imes {10^3} = {{100i} \over {10 	imes {{10}^{ - 2}}}}$$
$$ \Rightarrow i = 3A$$

Answer

$$30$$ $$mA$$

Answer

$$60$$ $$mA$$

Answer

$$3$$ $$A$$

Answer

$$6A$$

Magnetism and Matter

The coercivity of a small magnet where the ferromagnet gets demagnetized is $3 \times {10^3}\,A{m^{ - 1}}. The current required to be passed in a solenoid of length 10 cm and number of turns 100,$ so that the magnet gets demagnetized when inside the solenoid, is :

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