Q. A point charge of 40 stat coulomb is placed $2\ cm$ in front of an earthed metallic plane plate of large size. Then the force of attraction on the point charge is
A) $100\ dynes$
B) $160\ dynes$
C) $1600\ dynes$
D) $400\ dynes$
Explanation
(a) By the concept of electrical image, it is considered that an equal but opposite charge present on the other side of the plate at equal distance. Hence force
$F = \frac{40 \times 40}{4^{2}} = 100\ dynes$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.