Electric field strength?

Question

Determine the electrical field strength at a point midway between +5.00*10^-6C and a -5.00*10^-6C charge separated by 10cm.

Answer 1

q1=+5.00*10^-6C

q2= -5.00*10^-6C

d=10 cm

r=d/2=5 cm=0.05 m

k=1/(4πε₀)~9*10^9 N*m^2/C^2

|E|=k*q/r^2

|E1|=|E2|=9*10^9*5*10^-6/0.05^2=18 MV/m

vector E=vector E1+vector E2

|vector E|=|vector E1|+|vector E2|=

2*18=36 MV/m