Electric field and electric potential for point charges problem

[sbeal]

Homework Statement

Given two 1.80 µC charges at +/- 0.800 m from the origin and a positive test charge q = 1.30x10-18 C at the origin. What is the electric field at the origin due to the two 1.80 µC charges? What is the electrical potential at the origin due to the two 1.80 µC charges? related equations
E=KQ/r^2 electric field
V=KQ/r electric potential

The Attempt at a Solution

So for the electric field i tried plugging in 1.8E-6 C for Q and .8^2 for r then i added it to the same calculation only using -.8^2 in the second part. I am assumming that adding them both up would get the total electric field at the origin. I don't know how the charge at the origin comes into play because the radius is zero at the origin.
I ran into the same issue when trying to calculate the electric potential.

 

[willem2]

the question asked for the field and the potential due to the 2 $1.8 \mu C$ charges, so you can ignore the other one.

 

[nameoftherose]

can i ask a question?
i'm not finding how to start a thread.
i want to write a story about a star system that has no electro-magnetism.
can anybody enlighten me on what would be necessary for that to come about? (Theorectically)
cheers