(adsbygoogle = window.adsbygoogle || []).push({}); 1. Consider the electric dipole on the x-axis where a positive charge q is at (a,0) and a negative charge -q is at (-a,0) such that the distance between the two charges is 2a. Show that the electric field at a distant point on the +x axis is

E(x)= 4kqa/x^3.

2. Relevant equations: E=kq1q2/r^2

3. The attempt at a solution:

E=kq/x^2 - kq/(x+2a)^2

E(simplified)=kq[x^-2 - (x^2+4a)^-1]

E=4kqa/(x^4+4x^2a)

This clearly gives me the wrong solution, but I know it works when I switch my r values.

Why is it that I have to use x-a and x+a for r instead of x and x-2a?

Why does shifting the y-axis change the answer since x>>2a, it shouldn't matter, but I'm getting a different solution using this approach.

Please help me understand this problem! Thanks!

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# Homework Help: Electric Field at a Distant Point

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