Question

Positive electric charge QQ is distributed uniformly along a thin rod of length 2aa. The rod lies along the xx-axis between x=−ax=−a and x=+ax=+a (Figure 1). Calculate how much work you must do to bring a positive point charge qq from infinity to the point x=+Lx=+L on the xx-axis, where L>aL>a.

What does your result for the potential energy U(x=+L) become in the limit a→0? Express your answer in terms of some or all of the variables Q, q, a, L, electric constant ϵ0, and π

Answer 1