CBSE Class 12-science Answered
(a) An equipotential surface is a surface with a constant value of potential at all points on the surface.
Equipotential surfaces for two identical positive charges.
(b) First, we calculate the work done in bringing the charge q1 from infinity to r1.
Work done in this step is q1 V (r1).
Next, we consider the work done in bringing q2 to r2. In this step, work is done not only against the external field E but also against the field due to q1.
Work done on q2 against the external field = q2V (r2)
Work done on q2 against the field due to q1,
where r12is the distance between q1and q2. By the superposition principle for fields, we add up the work done on q2 against the two fields (E and that due to q1):
Work done in bringing q2 to r2= q2 V(r2) +
Thus,
Potential energy of the system
= the total work done in assembling the configuration