Question

A bar marget is demagnetized by placing it inside a solenoid of length $20cm$, $500$ turns & carrying current of $4.8A$. The coercivity of bar magnet material is

• A. $24\times {10}^{3}A/m$
• B. $12\times {10}^{3}A/m$
• C. $48\times {10}^{3}A/m$
• D. $36\times {10}^{3}A/m$

Answer 1

The correct option is B $12\times {10}^{3}A/m$

$H=\frac{B}{{\mu }_o}H=\frac{B}{{\mu }_o}=\frac{\text{/}{\mu }_{0}ni}{\text{/}{\mu }_o}=\frac{N}{l}i=\frac{500}{0.2}\times 4.8=500\times 24=12\times {10}^{3}A/m$