Q. A charged particle of mass $5 \times 10^{- 5}kg$ is held stationary in space by placing it in an electric field of strength $10^{7}NC^{- 1}$ directed vertically downwards. The charge on the particle is
A) $- 20 \times 10^{- 5}\mu C$
B) $- 5 \times 10^{- 5}\mu C$
C) $5 \times 10^{- 5}\mu C$
D) $20 \times 10^{- 5}\mu C$
Explanation
(b) $QE = mg \Rightarrow Q = \frac{mg}{E} = \frac{5 \times 10^{- 5} \times 10}{10^{7}} = 5 \times 10^{- 5}\mu C$
Since electric field is acting downward so for balance charge must be negative
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.