Two metallic spheres which have equal charges, but their radii are different, are made to touch each other and then separated apart. The potential the spheres will be 

Two spheres of radii $R$ and $2R$ are given a source equally positive charged and then connected by a long conducting wire, then the positive charge will

At a certain distance from a point charge, the electric field is $500 \mathrm{V} {\mathrm{m}}^{-1}$ and the potential is $3000 \mathrm{V}$. What is the distance?

Figure represents a square carrying charges $+q,+q,-q,-q$ at its four corners as shown. Then the potential will be zero at points