# Homework Help: Electric potential Energy/ electric potential

1. Feb 2, 2005

### Ksingh30

Can some please explain the difference between "Electric potential Energy & electric potential" and when a problem is asking you to find the potential difference which is it asking for?

2. Feb 2, 2005

### MathStudent

Potential is just the amount of potential energy per unit of charge,
thus for a point charge with charge q and potential energy U

[tex] V = \frac{U}{q} [/itex]

Another way of saying this is that V is the potential energy a point charge of 1C would have.

As you know the change in potential energy $\Delta U$ can be used to find the amount of work done by a conservative force.

Thus $\Delta V$ tells us the amount of work done per unit of charge by an electric field.

Or again, another way of saying this is that $\Delta V$ is the amount of work done on a point charge of 1C by an electric field.

3. Feb 2, 2005

### Ksingh30

wow

im still confused. I dont understand. This is the first topic in physics so far that has me confused.

4. Feb 2, 2005

### MathStudent

which part confuses you?
Do you know what potential energy is? If not then potential won't make any sense no matter how its explained.

5. Feb 3, 2005

### Ksingh30

oh wait

I think I just got it. correct me if im wrong please. if a charge enters a uniform electric field and it moves from point A to point B. The work done to move it from point Ato B=FD(distance moved), and if the charge moved towards the Low PE. it gained kinetic energy therefore it lost PE. so the change in PE(electric potential)=-W(work done to move from A to B)= -FD. and then the potential diference (V). the chance in V= change in PE/ q(the charge)
well?

6. Feb 3, 2005

### Ksingh30

charge

im assuming the charge is positive

7. Feb 3, 2005

### MathStudent

a few corrections but for the most part your right., my corrections are in bold

This is one very specific example

8. Feb 3, 2005

### maverick280857

With no intention to confuse you further (believe me mate, this can really kill you if you don't do it properly...) I'd like to add that in most texts, the external agent applies a force on the charge which is equal and opposite to the electrostatic force on it. This is because it is desired that the object be moved with zero acceleration. This is a very essential idea in electrostatics and you'll use it (sometimes unconsciously) in future.

9. Feb 3, 2005

### ZapperZ

Staff Emeritus
Just to add to what has been said here, an "electric potential" is due to the "field", whereas an "electric potential energy" is due to some test charge IN that field.

Let's say something somewhere creates an electrostatic field. Then the electric potential is the potential at some location in space due to this field. Only when you put a test charge Q at that location, is there now an electric potential energy, since you can now make a statement about work done in moving that charge from a 0 potential reference point to that location.

Notice that we are saying nothing about the field generated by Q itself. Q is simply a test charge residing within this already-created external field. [Q interacting with its own field is what is crudely defined as the self-energy interaction]

Zz.