1. Apr 8, 2012

### Boody

1. The problem statement, all variables and given/known data

I know that the work done by an electrostatic force is given by :

W = Fdcosθ (scalar product)
W = qE d cosθ

and I know that the electric potential is V = -W/q ,
where the work here is the work done by the electrostatic force.

2. The attempt at a solution

I have found that the work done by the electrostatic force is positive ,whether it is attraction or repulsion ( of course when the displacement is with the direction of the force)
(to see that apply the work equation to a positive charge +q and negative charge -q)

with that result ( when electrostatic force acts alone , the work done is +ve whether attraction or repulsion) ,

we (or I ) see that V = -W/q is negative when q is positive and positive when q is negative

why is that ?
and , how to interpret that (V is -ve for +ve charge , V is +ve for -ve charge) ?
I am looking for a conceptual answer , I do not need so much mathematical explanation.

Thanks

2. Apr 9, 2012

### BruceW

Yes, if a charged particle moves in the direction of the electrostatic force on it, then the work done by the electrostatic force on the charged particle is positive.

I'm not sure about V=-W/q ... I use V=W/q ... maybe your teacher was explaining specifically about an electron, which has negative charge, and using q to mean the absolute value of the electron's charge? Or maybe he was using W to mean work done by the system on the electromagnetic field?