JEE Main · 2024 · 08 Apr 2024 · Shift 2 · Magnetic Properties of Matter

The coercivity of a magnet is

5 \times 1 0^{3} A / m

. The amount of current required to be passed in a solenoid of length 30 cm and the number of turns 150, so that the magnet gets demagnetised when inside the solenoid is ______ A.

Answer: 10

Solution

Coercivity is the field intensity needed to reduce the residual magnetisation to zero, given for a solenoid by

H_{c} = \frac{ni}{ℓ}

Here

n = 150

ℓ = 0.3

H_{c} = 5 \times 1 0^{3}

A/m.

5 \times 1 0^{3} = \frac{150 i}{0.3} = 500 i ⟹ i = 10 A

JEE Main · 2024 · 08 Apr 2024 · Shift 2 · Integer answer

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