## PHYS208 Fundamentals of Physics II

### Hint for Ch. 23, 25P

Remember the geometry that I set up for the conjugate pairs in the case of the charged ring.
Switch to opposite charges and adjust the **E** contributions accordingly.

### First Hint for Ch. 23, special problem

Consider charge elements that are conjugate about the perpendicular bisector of P.
The contribution to E from the negative and positive infinitesimal elements will
combine to point down, horizontal components cancelling. The result for the point
dipole (Ch. 23: 25P) can be used for the conjugate pair and the linear charge
density integrated from 0 to a.

### Second Hint for Ch. 23, special problem

If you span the charge distribution as shown,
the following integral should result...

with the direction of **E** downward.

"http://www.physics.udel.edu/~watson/phys208/exercises/hints/0227.html"

Last updated Feb. 27, 1998.

Copyright George Watson, Univ. of Delaware, 1997.