Old Guy
- 101
- 1
Homework Statement
Given the following charges, all on the x-axis:
-q at x=-d
+2q at x=0
-q at x=d
Show that the electric field at a point (x,y) = (0,r) (ie, on the y-axis a distance r from the origin) is approximately:
\frac{3qd^2}{4\pi\epsilon_{0}r^4}
Homework Equations
The Attempt at a Solution
We were asked for an approximation, but it seems to me that an exact solution is relatively straightforward. The direction of the field from the positive charge would be along the y-axis. The field resulting from the negative charges would be from y=r toward those charges, but the x-components of those fields would cancel. Consequently, shouldn't the field simply be the field produced at r by the positive charge, minus the y-components of the fields produced by the negative charges? Am I missing something?