Two point charges q and q' are placed respectively at two points A and B. Let O be the midpoint of [AB].

Charge q placed at A creates at O an electric field of strength E=9×10^6 V/m.

Determine the resultant electric field at O when:
a) q'=q
b) q'=-q

1 answer

a) zero obviously
b) can't really tell. just saying E = 9e6 half way tells you nothing about the individual charges. Is one positive and the other negative? Are both positive?