Two pith balls each with mass $m$ are suspended from insulating threads. When the pith balls are given equal positive charge $Q$, they hang in equilibrium as shown. We now increase the charge on the left pith ball from $Q$ to $2Q$ while leaving its mass essentially unchanged. Which of the following diagrams best represents the new equilibrium configuration?

 

For two equal and opposite charges placed at distance $d$, then electric field will be zero at

In which regions, electric field can be zero for given arrangement of an electron and two protons?

The linear charge density upon the semi-circular ring, on both side is same in magnitude, the electric field at $O$ is along

An infinite long thread carries a charge uniformly spread over its length. It is bent in the form as shown. If the charge per unit length is $\lambda$, the electric field at point $O$ is

An infinitely large non-conducting plane sheet of charge density $\sigma$ has a circular aperture of certain radius carved out of it. The electric field at a point which is at a distance $\text{'}a\text{'}$ from the centre of aperture is $\frac{\sigma }{2\sqrt{2}{\epsilon }_0}.$ The radius of aperture is

The electric field due to charged circular arc shown in following figure, at centre $O$ is

If $\lambda =1\mu \mathrm{C} {\mathrm{m}}^{–1}$, then electric field intensity at $O$ is