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A bar magnet has coercivity $4 \times 10^3 \mathrm{Am}^{-1}$. It is placed inside a solenoid of $12 \mathrm{~cm}$ length and 60 turns.
The current that should be passed through the solenoid to demagnetise the bar magnet is
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The current that should be passed through the solenoid to demagnetise the bar magnet is
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Verified Answer
The correct answer is:
$8A$
Coercivity of bar magnet, $\mathrm{H}=4 \times 10^3 \mathrm{~A} / \mathrm{m}$
Length of solenoid, $\mathrm{L}=12 \mathrm{~cm}=0.12$
Number of turns, $\mathrm{N}=60$ turns
$\mathrm{n}=\frac{\mathrm{N}}{\mathrm{L}}=\frac{60}{0.12}=500 \mathrm{turn} / \mathrm{m}$
Current, $i=\frac{H}{n}=\frac{4 \times 10^3}{500}=8 \mathrm{~A}$
Length of solenoid, $\mathrm{L}=12 \mathrm{~cm}=0.12$
Number of turns, $\mathrm{N}=60$ turns
$\mathrm{n}=\frac{\mathrm{N}}{\mathrm{L}}=\frac{60}{0.12}=500 \mathrm{turn} / \mathrm{m}$
Current, $i=\frac{H}{n}=\frac{4 \times 10^3}{500}=8 \mathrm{~A}$
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