A charge of +10 C is located at the point x = 0 and y = 1, and a charge of -5 C is at the point x = 0 and y = -1. Find the point on the y-axis at which net E = 0. [Ans.: 0, -5.828, 0 or 0, -0.1716, 0]
13. A point charge of 20 nC is located at the origin. Determine the magnitude and direction of E at point P(1,3,-4) m. [Ans.: 1.357 + 4.073 - 0.784 V/m]