Question

A long vertical wire carrying a current of 1A in the upward direction is placed in a region where a horizontal magnetic field of $2.0\times {10}^{-4}T$ exists from south to north. Find the point where the resultant magnetic field is zero.

• A. 1.0mm, to the west of the wire
• B. 1.0 mm, to the East of the wire
• C. 2.0 mmm to the North of the wire
• D. 2.0 mm, to the South of the wire

Answer 1

The correct option is A 1.0mm, to the west of the wire

$B=B_H\frac{{\mu }_{0}i}{2\pi r}=B_H\frac{2\times {10}^{-7}\times 1}{r}=2.0\times {10}^{-4}$
$r={10}^{-3}m$ west of the wire
= 1.0 mm west of the wire