A charged oil drop of mass $2.5 imes 10^{- 7}kg$ is in space between the two plates, each of area $2 imes 10^{- 2}m^{2}$ of a parallel plate capacitor. When the upper plate has a charge of $5 imes 10^{- 7}C$ and the lower plate has an equal negative charge, the oil remains stationary. The charge of the oil drop is [Take $g = 10\ m/s^{2}$]

Question

A charged oil drop of mass $2.5 	imes 10^{- 7}kg$ is in space between the two plates, each of area $2 	imes 10^{- 2}m^{2}$ of a parallel plate capacitor. When the upper plate has a charge of $5 	imes 10^{- 7}C$ and the lower plate has an equal negative charge, the oil remains stationary. The charge of the oil drop is [Take $g = 10\ m/s^{2}$]

Dr. Abubacker · Accepted Answer

(c) We know that
$qE = mg$
$\frac{qQ}{\varepsilon_{0}A} = mg\ or\ q = \frac{\varepsilon_{0}Amg}{Q}$
$= \frac{8.85 	imes 10^{- 12} 	imes 2 	imes 10^{- 2} 	imes 2.5 	imes 10^{- 7} 	imes 10}{5 	imes 10^{- 7}}C$
$= 8.85 	imes 10^{- 13}C$

Explanation

Reviewed by Dr. Abubacker

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