Q. The charge which will flow through a 200 $\Omega$ galvanometer connected to a 400 $\Omega$ circular coil of 1000 turns wound on a wooden stick 20 mm in diameter, if a magnetic field B = 0.012 T parallel to the axis of the stick decreased suddenly to zero is
A) $6.3\ \mu C$
B) 63 $\mu C$
C) 0.63 $\mu C$
D) 630 $\mu C$
Explanation
(a) $q = \frac{q\phi}{R} = \frac{NA\left( B_{2} - B_{1} \right)}{R} = \frac{N\ \pi r^{2}\left( B_{2} - B_{1} \right)}{R}$
$= \ \frac{1000 \times \pi \times 10^{- 4} \times (0.012 - 0)}{(200 + 400)}$
= 6.3 $\times 10^{- 6}C. = 6.3\ \mu C$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.