Question

A long straight wire is carrying a current of $12A$. The magnetic field at a distance of $8cm$ is $({\mu }_0=4\pi \times 10^{-7}N/A^2)$

• A. $2\times 10^{-4}Wb/m^2$
• B. $3\times 10^{-5}Wb/m^2$
• C. $4\times 10^{-4}Wb/m^2$
• D. $4\times 10^{-5}Wb/m^2$

Answer 1

Answer: (B)

Magnetic field $B=\frac{{\mu }_{0}I}{2\pi r}$
Given. $\mu =4\pi \times 10^{-7}N/A^2$,
$r=8cm=8\times 10^{-2}m$
$I=12A$
$B=\frac{4\pi \times 10^{-7}}{2\pi }\times \frac{12}{8\times 10^{-2}}$
$\Rightarrow B=3\times 10^{-5}Wb/m^2$