Six charges are placed at the corners of a regular hexagon as shown. If an electron is placed at its centre $O$,the force on it will be:

$F_g$ and $F_e$ represent the gravitational and electrostatic forces,respectively,between two electrons situated at a distance of $10 \ cm$. The ratio of $F_g/F_e$ is of the order of:

Two identical metallic spheres $A$ and $B$ when placed at a certain distance in air repel each other with a force of $F$. Another identical uncharged sphere $C$ is first placed in contact with $A$ and then in contact with $B$ and finally placed at the midpoint between spheres $A$ and $B$. The force experienced by sphere $C$ will be:

In the following four situations,charged particles are at an equal distance from the origin. Arrange them in order of the magnitude of the net electric field at the origin,starting from the greatest.

$A$ circular ring carries a uniformly distributed positive charge. The electric field $(E)$ and potential $(V)$ vary with distance $(r)$ from the centre of the ring along its axis as:

$A$ clock dial has point charges $-q, -2q, -3q, \ldots, -12q$ at the positions of the corresponding numbers on the dial respectively. The time at which the hour hand points in the direction of the net electric field at the centre of the dial is (Assume clock hands do not influence the net electric field). (in $:30$)