# Electric Potential

## Homework Statement

Particles of the charges q1=+5e (at origin) and q2=-15e are fixed in place with a separation of d=0.24m. With V=0 at infinity, what are the finite (a) positive and (b) negative values of x at which the net electric potential on the x axis is zero?

## Homework Equations

E=Kq/r

3. The problem I encounter
I can get the answer but I don't understand the position considered. Where do I consider my x value to be? Why don't we consider x to be greater than d? Why do we only consider for 0<x<d or x<d?

## Answers and Replies

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x is the point where the electric fields from the charges cancel each other out. There are only two such points. You can consider x>d if you like but you won't find a point where the fields cancel each other because the field of q2 is always stronger in that region.

But we are considering potential. Do we understand through electric field then use the equation of potential?

Well, the only difference in the formula for the field is the power of r so qualitatively it's the same. In the region x>d the magnitude of q2 potential is always greater than that of q1. I just thought fields are more intuitive and illustrate better why there are only two points.