Question

A demagnetize a small ferromagnet, a current of $2A$ is required to be passed in a solenoid of length $20cm$ and number of turns $100$. The coercivity of the magnet is:

• A. $5000A{m}^{-1}$
• B. $1000A{m}^{-1}$
• C. $1250A{m}^{-1}$
• D. $3750A{m}^{-1}$

Answer 1

The correct option is B $1000A{m}^{-1}$

${\mu }_{0}H={\mu }_{0}ni$

$coercivity=\frac{no.ofturns\times current}{l}$

$=\frac{100\times 2}{0.2}$

$=1000A{m}^{-1}$