Question 8 of 57

The coercivity of a magnet is $5 \times 10^3 \mathrm{~A} / \mathrm{m}$. The amount of current required to be passed in a solenoid of length $30 \mathrm{~cm}$ and the number of turns 150 , so that the magnet gets demagnetised when inside the solenoid is _____A.

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Answer: 10

$\begin{aligned} & \mathrm{H}_{\mathrm{c}}=\frac{\mu_{\mathrm{o}} \mathrm{ni}}{\mu_{\mathrm{o}}} \\ & 5 \times 10^3=\frac{150}{30} \times 100 \times \mathrm{i} \\ & \frac{50}{5}=\mathrm{i} \\ & \mathrm{I}=10\end{aligned}$