i need to solve the point where the electric field is zero if q1=-5 coulumb and q2=+2 coulomb.both charge is located horizontally wher q2 is at the right side of q1 thanks
"This point is at infinity theoritically" Untrue, the electric fields will theoretically span to infinity, the field will approach zero, of course, at infinity. You will find the following link extremely useful, since it has a similar problem. I am still repressing my electromagnetics physics class and do not wish to look at it again http://physics.bu.edu/~duffy/PY106/Electricfield.html Steve Steve
I believe you need to know the distance between the charges, before you can find the point where the field is zero.