This question is actually the simplification of a more complicated one. A particle of charge +q is placed at a point A while another particle of charge +2q is placed at B, a distance of 2r to the right of A. The midpoint between the distance is denoted as O. What is the electric field intensity at O ?
The Attempt at a Solution
Honestly, if particle A has a charge of +q and if B has a charge of +q, then the electric field at O ought to be zero as they cancel each other out. But I can't understand it mathematically. Suppose I consider the electric field at point O due to the particle at A, then it's electric field E(A)=(kq)/(r^2) and the electric field at point O due to particle B E(B)=(k2q)/(r^2) where k=(1/4∏ε0) Hence the total electric field E(T)=E(A)+E(B)=(3kq)/(r^2) ??? Isn't it supposedly zero ? One might say that I ought to subtract them, but my textbook says that the electric field due to multiple charges is the vector sum of the individual electric fields. (Like the principle of superposition). Please advise on my mistake. Thank you.