Chapter 20, Problem 88GP

Predict/Calculate The three charges shown in Figure 20-33 are held in place as a fourth charge, q, is brought from infinity to the point P. The charge q starts at rest at infinity and is also at rest when it is placed at the point P. (a) If q is a positive charge, is the work required to bring it to the point P positive, negative, or zero? Explain. (b) Find the value of q if the work needed to bring it to point P is −13 × 10^-11 J.