Question

Define equipotential surface.

Answer 1

Hint: Look carefully at the name. Equi means equal so the name itself defines the entity. Surface with equal potential. Now try to think what gives a point or surface its potential and what entity should be common between points to have equal potential.

Complete step-by-step answer:
Surfaces across which potential is constant is called equipotential surface. The potential of any two points on the surface is the same and the potential difference between any two points on the equipotential surface is zero.
Equipotential surfaces are observed as both equal gravity potential and equal electric potential surfaces.
As all the surfaces have equal potential, the work done on moving any charged body across an equipotential surface will be zero, as the potential difference between the two points is zero.

Additional Information:
There are some properties of the equipotential surface that makes them so important in the electrodynamics problems: -
The angle between electric field lines and the surface is 90 is the case of equipotential surfaces. i.e. the electric field lines are normal to the equipotential surface.
An extension of the previous property is that the tangential component of the electric field lines alongside an equipotential surface is zero.
Two different equipotential surfaces can never coincide or intersect, as at the intersection point there would have to be two different potentials, one for each equipotential surface, which is not possible.

Note: Equipotential surfaces due to different charges are different. For a point charge, the equipotential surfaces are concentric spheres equidistant from the charge. While an infinitely large sheet would generate equidistant sheets as equipotential surfaces. Also, students should remember that the space between two or more sets of equipotential surfaces with the same difference in potentials of the surfaces help us determine the strength of the electric field.