Q. A point charge $q$ produces an electric field of magnitude 2${NC}^{- 1}$ at a point distance 0.25 m from it. What is the value of charge?
A) $1.39 \times 10^{- 11}$ C
B) $1.39 \times 10^{11}$ C
C) $13.9 \times 10^{- 11}$ C
D) $13.9 \times 10^{11}$ C
Explanation
(a) Electric field,
$E = \frac{q}{4\pi\varepsilon_{0}r^{2}}$
$q = 4\pi\varepsilon_{0}\ r^{2}E$
$= \frac{(0.25)^{2} \times 2}{9 \times 10^{9}}$
$q = 1.39 \times 10^{- 11}C$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.