CBSE Class 11-science Answered

Generally we speak of potential difference between two points.

At times we may speak of the potential at a point. But in that case also we always refer it to some other, agreed, reference point as a 'zero' of potential.

You might find it easier to understand if you look at an analogy, the height of a mountain refers to its height above sea-level. Here the sea level is the zero of height. Even if we do not mention it we know that the height of a place is being referred to with respect to sea level.

Similarly for potential we need to define a zero which is used as a reference point. This is not taken as the surface of the earth but it is  infinity.

Potential at point A now becomes the work done per coulomb in bringing a positive charge from infinity to A.