What is the magnitude of a point charge due to which the electric field 30cm away has the magnitude $2\;newton/coulomb$ $[1/4\pi {\varepsilon _0} = 9 imes {10^9}N{m^2}/{C^2}]$

Let ${E_a}$ be the electric field due to a dipole in its axial plane distant $'l'$ and let ${E_q}$ be the field in the equatorial plane distant $'l'$ then the relation between ${E_a}$ and ${E_q}$ will be

An insulated sphere of radius $R$ has charge density $\rho$. The electric field at a distance $r$ from the centre of the sphere $\left( {r < R} \right)$

Two small spheres each carrying a charge $q$ are placed $r$ metre apart. If one of the sphere is taken around the other one in a circular path of radius $r$, the work done will be equal to

A charge $q$ is placed at centre of the line joining two equal charges Q. The system of 3 charges will be in equilibrium of $q$ is equal to

A metallic sphere of radius $15$ cm carries a charge of $4.8 imes 10^{-7}$ C uniformly distributed over its surface. Calculate the magnitude of the electric field at a point $25$ cm away from the center of the sphere. (Given: $\frac{1}{4\pi\epsilon_0} = 9 imes 10^9 Nm^2/C^2$)

The electric field due to a charge at a distance of $3m$ from it is $500N/{\rm{coulomb}}{\rm{.}}$ The magnitude of the charge is $\left[ {\frac{1}{{4\pi {\varepsilon _0}}} = 9 imes {{10}^9}\frac{{N - {m^2}}}{{coulom{b^2}}}} \right]$

The electric field in the space between the plates of a discharge tube is

$3.25 imes {10^4}\;{\rm{N}}{{\rm{C}}^{ - 1}}$. If mass of proton is 1.67$imes {10^{ - 27}}{\rm{\;kg}}$ and its charge is 1.6$imes {10^{ - 19}}{\rm{C}}$, the force often the proton in the field is

Infinite charges of magnitude q each are lying at $x = 1,2,4,8..$ metre on X-axis. The value of intensity of electric field at point $x = 0$ due to these charges will be

Two infinitely long parallel conducting plates having surface charge densities $+ \sigma$ and $-\sigma$ respectively, are separated by a small distance. The medium between the plates is vacuum. If ${\varepsilon _0}$ is the dielectric permittivity of vacuum, then the electric field in the region between the plates is

An electron enters between two horizontal plates separated by $2\;mm$ and having a potential difference of $1000\;V.$ The force on electron is