Question:
A bar magnet is demagnetized by inserting it inside a solenoid of length 0.2 m, 100 turns, and carrying a current of 5.2 A. The corecivity of the bar magnet is :
A bar magnet is demagnetized by inserting it inside a solenoid of length 0.2 m, 100 turns, and carrying a current of 5.2 A. The corecivity of the bar magnet is :
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Coercivity is the reverse magnetising field \(H=nI\) needed to bring the magnetisation to zero; \(n\) is turns per unit length.
Updated On: Nov 5, 2026
- 285 A/m
- 2600 A/m
- 520 A/m
- 1200 A/m
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The Correct Option is B
Solution and Explanation
The demagnetising field is supplied by the solenoid: \(H=nI\) with \(n=\frac{N}{L}=\frac{100}{0.2}=500\ \mathrm{turns/m}\).
\(H=500\times5.2=2600\ \mathrm{A/m}\).
This field just demagnetises the magnet, so coercivity \(=2600\ \mathrm{A/m}\).
Answer: (2) 2600 A/m
\(H=500\times5.2=2600\ \mathrm{A/m}\).
This field just demagnetises the magnet, so coercivity \(=2600\ \mathrm{A/m}\).
Answer: (2) 2600 A/m
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