Question

A current of $8$ A flows through a horizontal wire from east to west. If the horizontal component of the earth's magnetic field is $4$ x 10${}^{-5}$T, then the neutral point is ______

• A. Nor formed
• B. formed at $0.08$ m south of the wire
• C. formed at $0.06$ m above the wire
• D. formed at $0.04$ m below the wire

Answer 1

The correct option is D formed at $0.04$ m below the wire

Given,

I,current=8A

${\overrightarrow{B}}_H$, erath magnetic field=$4\times {10}^{-5}T$

For neutral point,

Magnetic field due to wire = earth horizontal magnetic field

$⟹\frac{{\mu }_{0}I}{2\pi R}={\overrightarrow{B}}_H$

$⟹R=\frac{{\mu }_{0}I}{2\pi B_H}=\frac{4\pi \times {10}^{-7}\times 8}{2\pi \times 4\times {10}^{-5}}=0.04m$ below the wire.