An oil drop of radius $2\, mm$ with a density $3\, g$ $cm ^{-3}$ is held stationary under a constant electric field $3.55 \times 10^{5}\, V\, m ^{-1}$ in the Millikan's oil drop experiment. What is the number of excess electrons that the oil drop will possess ? (consider $\left. g =9.81\, m / s ^{2}\right)$
$48.8 \times 10^{11}$
$1.73 \times 10^{10}$
$17.3 \times 10^{10}$
$1.73 \times 10^{12}$
Find ratio of electric field at point $A$ and $B.$ Infinitely long uniformly charged wire with linear charge density $\lambda$ is kept along $z-$ axis
A positively charged pendulum is oscillating in a uniform electric field pointing upwards. Its time period as compared to that when it oscillates without electric field
A charged particle of mass $0.003\, gm$ is held stationary in space by placing it in a downward direction of electric field of $6 \times {10^4}\,N/C$. Then the magnitude of the charge is
The point charges $Q$ and $-2Q$ are placed at some distance apart. If the electric field at the location of $Q$ is $\vec E$ , then the electric field at the location of $-2Q$ will be :
Write equation of electric field by system of $\mathrm{'n'}$ charges.