How to Calculate Potential Difference and Electric Field for a Point Charge?

[Mhchurch4]

1. Consider point a which is 70 cm north of a -4.2 µC point charge, and point b which is 74 cm west of the charge (Fig. 17-23).
(a) Determine Vba = Vb - Va.
(b) Determine Eb - Ea.
Magnitude
Direction (counterclockwise from east is positive)


2. Vb-Va=(EPEb/q)-(EPEa/q)



3. I thought I would use that formula since that is what I need, but I don't know how to get V. Please help!

 

[G01]

That formula is correct but work simplify it a little bit.

What is the electric potential energy at a point equal to? If you know, then fill that into the formulas you have to simplify. If you can do this you should end up with some workable formulas.