Question

The B-H curve for a ferromagnet is shown in the figure. The ferromagnet is placed inside a ling solenoid with $1000$ turns/cm.. The current that should be passed in the solenoid to demagnetise the ferromagnet completely is:

• A. $2mA$
• B. $1mA$
• C. $3mA$
• D. None of these

Answer 1

The correct option is B $1mA$

$N=1000turns/cm$

$H=\frac{NI}{l}$

$100\frac{A}{M}=\frac{1000\times I}{{10}^{-2}}$

$100A={10}^5\times I$

${10}^{-3}A=I$

$I=1mA$