What is the electric potential?

[Ammora]

Homework Statement

Consider the following figure.

image: http://www.webassign.net/grr/p17-18.gif"

(a) Find the electric potential at points a and b for charges of +3.5 nC and -7.6 nC located as shown in the figure.
Va= _____ V
Vb= _____ V


(b) What is the potential difference ΔV for a trip from a to b?
_____ V

(c) How much work must be done by an external agent to move a point charge of +1.50 nC from a to b?
_____ J

Homework Equations

v=Er?
U=kQ/r

The Attempt at a Solution

I tried multiplying the distance by the charge, which was wrong. Then I tried taking (1/4 pie epsilon not) (charge/r) which was wrong. I don't know what to do, can you please help?

 

[Delphi51]

Your U=kQ/r is not correct! Check the units.
It should read V = kQ/r.
The electric potential due to a charge Q at distance r is kQ/r.