Question

A flat coil of radius 0.7cm has 100 loops. It is placed in a magnetic field of induction 0.3T so that flux passes through it. It is rotated such that maximum flux passes through it again in 0.02s. Then induced emf in the coil is

• A. 0.15V
• B. 0.73 V
• C. 0.23 V
• D. 0.462 V

Answer 1

The correct option is D 0.462 V

$e=\frac{BAN[cos{\theta }_1-cos{\theta }_2]}{t}$
$=0.3\times \pi r^2\times 100\left[\frac{cos\left(0\right)-cos180}{0.02}\right]$
$=\frac{3\times 10}{2\times {10}^{-2}}\left[2\right]\times \frac{22}{7}\times 0.7\times 0.7\times {10}^{-4}$
$=3\times 22\times 10\times 7\times {10}^{-4}$
$=21\times 22\times {10}^{-3}$
$=0.462V$