The surface charge density of a conducting plate is $-2 \times 10^{-6} \ C/m^2$. An electron with energy $100 \ eV$ moves towards the plate and strikes it. What is the initial distance of the electron from the plate?

Two concentric conducting thin spherical shells of radii $a$ and $b$ $(b > a)$ are given charges $Q$ and $-2Q$ respectively. The electric field along a line passing through the centre as a function of distance $(r)$ from the centre is given by:

The electric potential $V(x)$ in a region around the origin is given by $V(x) = 4x^2 \text{ V}$. The electric charge enclosed in a cube of $1 \text{ m}$ side with its centre at the origin is (in coulomb):

Let there be a spherically symmetric charge distribution with charge density varying as $\rho (r) = \rho _0 \left( \frac{5}{4} - \frac{r}{R} \right)$ for $r \le R$,and $\rho (r) = 0$ for $r > R$,where $r$ is the distance from the origin. The electric field at a distance $r (r < R)$ from the origin is given by:

The electric field intensity due to an infinite cylindrical thin wire having charge $q$ per unit length at a distance $r$ from its axis is

An infinite line charge produces a field of $9 \times 10^4 \ NC^{-1}$ at a distance of $2 \ cm$. Its linear charge density is