$ + 2\,C$ and $ + 6\,C$ two charges are repelling each other with a force of $12\,N$. If each charge is given $ – 2\,C$ of charge, then the value of the force will be

Two charged spheres separated at a distance $d$ exert a force $F$ on each other. If they are immersed in a liquid of dielectric constant $2$, then what is the force (if all conditions are same)

Equal charges $q$ are placed at the four corners $A,\,B,\,C,\,D$ of a square of length $a$. The magnitude of the force on the charge at $B$ will be

Force between two identical spheres charged with same charge is $F$. If $75\%$ charge of one sphere is transfered to the other sphere then the new force will be

An infinite number of charges, each of charge $1 \,\mu C$ are placed on the $x$-axis with co-ordinates $x = 1, 2,4, 8, ….\infty$. If a charge of $1\, C$ is kept at the origin, then what is the net force acting on $1\, C$ charge….$N$