# Two Opposite Point Charges

## Collaborate

What would happen to a positive test charge placed very close to the positive charge (left half of the diagram)? Remain Stationary
Go out to infinity
Go to the negative charge
What is the value of the electric potential at the midpoint of two opposite point charges? What is the electric field at that point?
Imagine that two equal but opposite point charges approached each other until they were almost touching. What would this look like?
1. Find the potential V at point P. P is on a perpendicular bisector to the line connecting the two +Q charges, and is a distance z away from that line. Note that one charge is at +Q while the other is at -Q.
2. Can you find the electric field at this point using the same method as you would for two +Q charges? If not, explain why. If you can, calculate the field. (there is a similar question on a previous page).
3. What is the field in the limiting case z>>d (z much larger than d)? Can you explain this?

All done? Head over to the dipole page.