Question

A closely wound flat circular coil of $25$ turns of wire has diameter of $10cm$ and carries a current of $4$ amperes. determine the magnetic flux density at the centre of the coil:-

• A. $1.679\times {10}^{-5}T$
• B. $2.028\times {10}^{-4}T$
• C. $1.257\times {10}^{-3}T$
• D. $1.512\times {10}^{-6}T$

Answer 1

Answer: (C)

$1.257\times {10}^{-3}T$

The magnetic flux density at the center of coil:

$B={10}^{-7}\frac{2\pi ni}{r}$

$={10}^{-7}\times \frac{2\times \pi \times 25\times 4}{5\times {10}^{-2}}$

$=1.257\times {10}^{-3}T$