Q. A circular coil of diameter 21 cm is placed in a magnetic field of induction 10$^{-4}$ T. the magnitude of flux linked with coil when the plane of coil makes an angle 30${^\circ}$ with the field is
A) $1.44 \times 10^{- 6}\ Wb$
B) $1.732 \times 10^{- 6}\ Wb$
C) $3.1 \times 10^{- 6}\ Wb$
D) $4.2 \times 10^{- 6}\ Wb$
Explanation
(b) Magnetic flux , $\phi = \int_{}^{}{\mathbf{B}.\mathbf{dA}}\mathbf{=}BA\cos{\theta,}where\ \theta\ $is angle between normal to the area dA with magnetic field B.
Here, $\theta = (90{^\circ} - 30{^\circ}) = 60{^\circ}$
and $\theta = 10^{- 4} \times \pi\left\lbrack \frac{21}{2} \times 10^{- 2} \right\rbrack^{2} \times \cos{60{^\circ}}$
$\mathbf{\ \ \ \ \ \ \ \ \ \ \ \ =}1.732 \times 10^{- 6}Wb$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.