Question

Given the two charges +Q$+Q$ and Q1=−2Q/7$Q_1=-2Q/7$shown in (Figure 1), at what position x$x$ is the electric field zero? Express your answer in terms of distance d$d$.

Answer 1

as P due to Q = KQ/(d+x)^2

due to Q1 = 2kQ / 7(x^2)

net = kQ/(d+x)^2 - 2kQ / 7x^2   = 0

2(d+x)^2 = 7x^2

takeing root of both side

(d+x) = 1.87x

x = 1.15d