Question

A magnetising field of $5000\text{A/m}$ produces a magnetic flux of $5\times {10}^{-5}\text{wb}$ in an iron rod is $0.5{\text{cm}}^2$, then the permeability of the rod will be (in $\text{H/m}$)

• A. $2\times {10}^{-4}$
• B. $1\times {10}^{-3}$
• C. $4\times {10}^{-6}$
• D. $3\times {10}^{-5}$

Answer 1

The correct option is A $2\times {10}^{-4}$

$$\begin{array}{cc}H=5000\text{A/m}& \varphi =5\times {10}^{-5}\text{wb}\\ A=0.5{\text{cm}}^2& \end{array}$$

$\left(i\right):\varphi =\overrightarrow{B}\cdot \overrightarrow{A}$

$B=\frac{\varphi }{A}=\frac{5\times {10}^{-5}}{0.5\times {10}^{-4}}=1\text{T}$

$\left(ii\right):B=\mu H$

$\mu =\frac{B}{H}=\frac{1}{5000}=2\times {10}^{-4}\text{H/m}$