Question

A 800 turn coil of effective area 0.05 $m^2$ is kept perpendicular to a magnetic field $5\times 10^{-5}$ T. When the plane of the coil is rotated by $90^\circ$ around any of its coplanar axis in 0.1 s, the emf induced in the coil will be

• A. $2\times 10^3$V
• B. 0.02 V
• C. 2V
• D. 0.2 V

Answer 1

Answer: (B)

0.02 V

Answer 2

Magnetic field $B = 5 \times 10^{-5} \; T$
Number of turns in coil N = 800
Area of coil A = 0.05 $m^2$
Time taken to rotate $\Delta$t = 0.1 s
Initial angle $\theta_1 = 0^{\circ}$
Final angle $\theta_2 = 90^{\circ}$
Change in magnetic flux $\Delta \phi$
$= NBA \cos 90^{\circ} - BA \cos 0^{\circ}$
= - NBA
$= - 800 \times 5 \times 10^{-5} \times 0.05$
= - 2 $\times 10^{-3}$ weder
$e =- \frac{\Delta\phi}{\Delta t} = \frac{-\left(-\right)2\times10^{-3}Wb}{0.1 s} = 0.02 V$