Question

A closely wound flat circular coil of $25$ turns of wire has diameter of $5$cm which carries current of $4$ amperes, the flux density at the centre of a coil will be

• A. $1.256\times {10}^{-3}$ tesla
• B. $1.679\times {10}^{-5}$ tesla
• C. $1.512\times {10}^{-5}$ telsa
• D. $2.28\times {10}^{-4}$ telsa

Answer 1

The correct option is A $1.256\times {10}^{-3}$ tesla

Flux density, $B=\frac{{\mu }_{0}i}{2r}\times n$

$=\frac{4\pi \times {10}^{-7}\times 4\times 25}{2\times 5/100}$
$=\frac{4\pi \times {10}^{-7}\times (100{)}^2}{10}$

$=1.256\times {10}^{-3}$ tesla.