Question

The number of turns per unit length in a toroid is ${10}^3$ and current flowing in it is $\frac{1}{4\pi }$ ampere, then the magnetic induction produced in it, is :

• A. ${10}^{-4}T$
• B. ${10}^{4}T$
• C. ${10}^{-2}T$
• D. ${10}^{2}T$

Answer 1

Answer: (A)

${10}^{-4}T$

Magnetic field in a toroid $B={\mu }_{0}ni$
Given $n={10}^3$ and $i=\frac{1}{4\pi }A$
We know that ${\mu }_0=4\pi \times {10}^{-7}T/A$
$B=4\pi \times {10}^{-7}\times {10}^3\times \frac{1}{4\pi }={10}^{-4}T$