Question

A charged particle of mass $5\times {10}^{-6}kg$ is held stationary in space by placing it in an electric field of strength ${10}^{6}N{C}^{-1}$ directed vertically downwards. The charge on the particle is $(g=10m{s}^{-2})$:

• A. $-20\times {10}^{-5}\mu C$
• B. $-5\times {10}^{-5}\mu C$
• C. $5\times {10}^{-5}\mu C$
• D. $20\times {10}^{-5}\mu C$

Answer 1

The correct option is B $-5\times {10}^{-5}\mu C$

$F_e$=electric force on particle

$q$=charge on particle

Net force=$F_e+mg=0$

$⟹qE+mg=0$

$⟹q=-\frac{mg}{E}$

$⟹q=-\frac{5\times {10}^{-6}\times 10}{{10}^6}$

$⟹q=-5\times {10}^{-5}\mu C$

Answer-(B)