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 

If the distance between the plates of a capacitor having capacity $C$ and charge $Q$ is doubled then work done will be

Two equal point charges are fixed at $x = -a$ and $x = + \,a$ on the $x$-axis. Another  point charge $Q$ is placed at the origin. The change in the electrical potential energy of $Q$ ehen it is displaced by a small distance $x$ along the $x$ -axis is apporximately proportional to

Angle between equipotential surface and lines of force is.......$^o$

The electric potential $(V)$ as a function of distance $(x)$ [in meters] is given by $V = (5x^2 + 10 x -9)\, Volt$. The value of electric field at $x = 1\, m$ would be......$Volt/m$

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