A long straight wire carries a current of 35 A. The magnitude of the field B at a point 20 cm from the wire would be:

$3.5 × 10^{-5} T$

The correct answer is Option (3) → $3.5 × 10^{-5} T$

Magnetic field around a straight wire -

$B=\frac{μ_0I}{2πr}$

I (Current) = 5 A

$r$ (distance from wire) = 0.20 m

$∴B=\frac{4π×10^{-7}×35}{2π×0.20}$

$=3.5 × 10^{-5} T$