Question

The corecivity of a bar magnet is $100\text{A/m}$. It is to be demagnetised by placing it inside a solenoid of length $100\text{cm}$ and number of turns $50$. The current flowing through the solenoid will be:

• A. $4\text{A}$
• B. $2\text{A}$
• C. $1\text{A}$
• D. Zero

Answer 1

The correct option is B $2\text{A}$

Given, corecivity, $\left(H\right)=100\text{A/m}$

Length of solenoid $=100\text{cm}$

Number of turns per metre $=50$

$H=\frac{B}{{\mu }_0}$

$\Rightarrow H=nI(\because B={\mu }_{0}nI)$

$\Rightarrow 100=50\times I$

$\Rightarrow I=2\text{A}$

Hence, option $\left(B\right)$ is the correct answer.