Q. A tangent galvanometer has a coil with 50 turns and radius equal to $4\ cm$. A current of $0.1\ A$ is passing through it. The plane of the coil is set parallel to the earth’s magnetic meridian. If the value of the earth’s horizontal component of the magnetic field is $7 \times 10^{- 5}tesla$ and $\mu_{0} = 4\pi \times 10^{- 7}weber/amp \times m$, then the deflection in the galvanometer needle will be
A) $45{^\circ}$
B) $48.2{^\circ}$
C) $50.7{^\circ}$
D) $52.7{^\circ}$
Explanation
(b) For tangent galvanometer $I = \frac{2rB}{\mu_{0}n}\tan\theta$
$\therefore\tan\theta = \frac{I\mu_{0}n}{2rB} = \frac{0.1 \times 4\pi \times 10^{- 7} \times 50}{0.04 \times 7 \times 10^{- 5} \times 2} = 1.12$
or $\theta = \tan^{- 1}{(1.12)} = 48.2{^\circ}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.