Question

Calculate the flux density at a distance of 1 cm from a very long straight wire carrying a current of 5A. At what distance from the wire will the field flux density neutralize that due to the earth's horizontal component flux density $2\times {10}^{-5}T?({\mu }_0=4\pi \times {10}^{-7}H{m}^{-1})$

Answer 1

$B=\frac{{\mu }_{0}I}{2\pi a}=\frac{4\pi \times {10}^{-7}\times 5}{2\pi \times 1\times {10}^{-2}}={10}^{-4}T$
For the second part,
$a=\frac{{\mu }_{o}I}{2\pi B}=\frac{4\pi \times {10}^{-7}\times 5}{2\pi \times 2\times {10}^{-5}}=5\times {10}^{-2}=5cm$