A particle (charge = +4.0 nC) is located on the x-axis at the point x = -20.0 m, and a second particle (charge = -10.0 nC) is placed on the x-axis at x=+8.0 m. What is the magnitude of the total electrostatic field (in N/C) at the origin (x=0)?

Answer 1

Add the two components...

Et=E1+E1=k4/20^2+k10^2/8^2

negative sign points to minus x axis, so in this case, E is to the right