Two electrons are moving towards each other,each with a velocity of $10^6 \, m/s$. What will be the closest distance of approach between them in $m$?

Two charges are at a distance $d$ apart. If a copper plate (conducting medium) of thickness $d/2$ is placed between them,the effective force will be

Two charges $q_1 = +6q$ and $q_2 = -3q$ are placed as shown in the figure. $A$ proton is placed on the $x$-axis away from $q_2$. To keep the proton in equilibrium,the distance between $q_1$ and the proton is:

$A$ and $B$ are two identical blocks made of a conducting material. These are placed on a horizontal frictionless table and connected by a light conducting spring of force constant $K$. The unstretched length of the spring is $L_0$. $A$ charge $Q/2$ is given to each block. Consequently,the spring stretches to an equilibrium length $L$. The value of $Q$ is

Two point charges of $1 \, \mu\text{C}$ and $5 \, \mu\text{C}$ are placed at a distance of $4 \, \text{cm}$ apart. The ratio of the forces exerted by them on each other will be:

In the figure,the force on the charge at $A$ in the direction perpendicular to $BC$ is ...... .