Question

A transmission line carries a current of 100 A in east to west direction.Find magnitude of the magnetic field due to current at a distance 1m below the wire

• A. $2\times {10}^{-5}T$
• B. $2\times {10}^{5}T$
• C. ${10}^{5}T$
• D. ${10}^{-5}T$

Answer 1

The correct option is A $2\times {10}^{-5}T$

Answer is A.
The magnitude of the magnetic field, B is expressed as B = $\frac{{\mu }_{0}I}{2\pi r}$.
Substituting the values of ${\mu }_0$, I and r as $4\pi \times {10}^{-7},100Aand1m$ respectively,
Then, B = $\frac{4\pi \times {10}^{-7}\times 100}{2\times \pi \times 1}=2\times {10}^{-5}Wb/m^2=2\times {10}^{-5}T$.
Hence, the magnitude of the magnetic field due to current at a distance 1 m below the wire is $2\times {10}^{-5}T$.