Question

The corecivity of a small magnet where the ferromagnet gets demagnetized is $3\times {10}^{3}A{m}^{-1}$. The current required to be passed in a solenoid of length $10cm$ and number of turns $100$, so that the magnet gets demagnetized when inside the solenoid is:

• A. $30mA$
• B. $3A$
• C. $6A$
• D. $60mA$

Answer 1

Answer: (B)

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

$n=\frac{N}{L}=\frac{100}{0.1}$

$3\times {10}^3=\frac{100}{0.1}i$

$i=3A$