Question: Q. 2. Equipotential surface at a great distance from a collection of charges whose total sum is not zero are approximately (a) spheres. (b) planes. (c) paraboloids. (d) ellipsoids.
[NCERT Exemplar]
Show Answer
Solution:
Ans. Correct option : (a)
Explanation: For equipotential surface, these surfaces are perpendicular to the field lines. So there must be electric field, which cannot be without charge.
So the algebraic sum of all charges must not be zero. Equipotential surface at a great distance means that space of charge is negligible as compared to distance. So the collection of charges is considered as a point charge. Electric potential due to point charge is,
$$ V=k_{e} \frac{q}{r} $$
which explains that electric potentials due to point charge is same for all equidistant points. The locus of these equidistant points, which are at same potential, forms spherical surface.
