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.

 

[rwisz]

The reasoning in your textbook is correct. In the context of electric potential, only differences in potential energy are important because the absolute value of potential energy is not relevant. What matters is the difference in potential energy between two points, which is represented by the potential difference.

The definition of potential includes potential energy, but it is important to note that potential energy is a measure of the work required to move a charge from one point to another in an electric field. This means that the potential energy is dependent on the path taken between the two points, whereas potential difference is not.

For example, if we have two points A and B with a potential difference of 10 volts, it means that it takes 10 joules of work to move a charge from A to B. However, the path taken between A and B does not affect this potential difference. Whether we take a straight line path or a curved path, the potential difference will remain the same. This is why only the difference in potential is important.

Additionally, potential is a scalar quantity, meaning it only has magnitude and no direction. This further supports the idea that only the difference in potential matters, as it does not have a specific direction associated with it.

I hope this helps clarify the concept of electric potential differences for you. If you have any further questions, please let me know.