Understanding Electric Potential Differences

[nicksbyman]

This isn't a homework problem but is rather me trying to understand a concept. So here it is:

My textbook says that because only differences in potential energy are important, only differences in potential (electric potential) are important. How is this reasoning correct? The definition of potential has potential energy in it: PE/q, so this needed difference of potential ENERGY is already accounted for.

Thanks :)

 

[rock.freak667]

Usually definitions for gravitational potential and electric potential show the energy needed to move unit mass or charge from a point to infinity. In most cases, you don't want to move from point A to infinity but from point A to B. So you only need the difference in potential between A and B to know how much energy is needed.

 

[nicksbyman]

Usually definitions for gravitational potential and electric potential show the energy needed to move unit mass or charge from a point to infinity. In most cases, you don't want to move from point A to infinity but from point A to B. So you only need the difference in potential between A and B to know how much energy is needed.

But I don't want to know how much energy is needed, I only want to know what the potential is.

 

[rock.freak667]

But I don't want to know how much energy is needed, I only want to know what the potential is.

If you wish to the potential then just use the formula for it. If you want the potential difference then subtract the two potentials. Potential itself is sort of a difference as the potential energy at infinity is zero.