A ring of radius $R$ is charged uniformly with a charge $+\,Q$ . The electric field at a point on its axis at a distance $r$ from any point on the ring will be
$\frac{{KQ}}{{({r^2} - {R^2})}}$
$\frac{{KQ}}{{{r^2}}}$
$\frac{{KQ}}{{{r^3}}}{({r^2} - {R^2})^{1/2}}$
$\frac{{KQr}}{{{R^3}}}$
Mention characteristics of electric field.
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 $\left. g =9.81\, m / s ^{2}\right)$
In the following four situations charged particles are at equal distance from the origin. Arrange them the magnitude of the net electric field at origin greatest first
Give physical meaning of electric field.
The electric field intensity at a point in vacuum is equal to