Question

At what distance from a long straight wire carrying a current of $12A$ will the magnetic field be equal to $3\times {10}^{-5}Wb/m^2$ ?

• A. $8\times {10}^{-2}m$
• B. $12\times {10}^{-2}m$
• C. $18\times {10}^{-2}m$
• D. $24\times {10}^{-2}m$

Answer 1

The correct option is A $8\times {10}^{-2}m$

Given,

$B=3\times {10}^{-5}Wb/m^2$

$i=12A$

The magnetic field at a distance $r$ from the long current carrying straight wire is given by,

$B=\frac{{\mu }_{0}i}{2\pi r}$

$r=\frac{{\mu }_{0}i}{2\pi B}$

$r=\frac{4\pi \times {10}^{-7}\times 12}{2\pi \times 3\times {10}^{-5}}$

$r=8\times {10}^{-2}m$

The correct option is A.