Question

The coercitivity of a small magnet where the ferromagnet gets demagnetised is 3×10³ Am⁻¹ . The current required to be paased in a selenoid of length 10cm and number of turns 100 , so that the magnet gets demagnetised when inside the selenoid is [JEE main 2014] ​

Answer 1

Answer:

The magnet gets demagnetised when inside the solenoid have 3A current

Explanation:

For solenoid , the magnetic field needed to be magmetised , the magnet is given by

B = μ₀nI

where, n is number of turns per unit length = N/L

and, N = 100, L = 10 cm = 10/100= 0.1m

=> 3× 10³ = 100/0.1 × I

=> I = 3×10²/100 = 300/100

=> I = 3A Answer

Answer 2

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I = 3 A