Question

The space inside a toroid is filled with tungsten whose susceptibility is $6.8\times {10}^{-5}$. The percentage increase in the magnetic field will be :

• A. $0.68\%$
• B. $0.068\%$
• C. $0.0068\%$
• D. $6.8\%$

Answer 1

The correct option is C $0.0068\%$

$B_{toroid}=\mu nI$
$B={\mu }_{0}nI$
$B^{\prime }={\mu }_0{\mu }_{r}nI$
${\mu }_r=1+\chi$
$\%$ increase = $\frac{B^{\prime }-B}{B}$
$=6.8\times {10}^{-3}\%$