Question

A circular coil of wire consisting of 100 turns, each of radius 8 cm carries a current of 0.40 A What is the magnitude of the magnetic field B at a point 20 cm from the wire?

• A. $=6.14\times {10}^{-4}T$
• B. $=4.14\times {10}^{-4}T$
• C. $=3.14\times {10}^{-4}T$
• D. $=5.14\times {10}^{-4}T$

Answer 1

The correct option is C $=3.14\times {10}^{-4}T$

$B={\mu }_o\frac{2\pi NI}{4\pi r}$

$=\frac{4\pi \times {10}^{-7}\times 2\pi \times 100\times 0.4}{4\pi \times 0.08}$

$=3.14\times {10}^{-4}T$