Electric field inside a uniformly charged sphere of radius $R,$ is ($r$ is distance from centre, $r < R$)

Four charges equal to $-Q$ are placed at the four corners of a square and a charge $q$ is at its centre. If the system is in equilibrium, the value of $q$ is

In a certain region of space, there exists a uniform electric field of value $2\times10^2\hat k\, Vm^{-1}$. A rectangular coil of dimension $10\, cm\times20\, cm$ is placed in the $xy$ plane. The electric flux through the coil is......$Vm$

The plates of a parallel plate capacitor are charged up to $100\,volt$. A $2\,mm$ thick plate is inserted between the plates, then to maintain the same potential difference, the distance between the capacitor plates is increased by $1.6\,mm$. The dielectric constant of the plate is 

A given charge is situated at a certain distance from an electric dipole in the axial position experiences a force $F$ . If the distance of the charge is doubled, the force acting on the charge will be

 An insulator plate is passed between the plates of a capacitor. The the displacement current