hw5 - Electricity and Magnetism I(P331 Homework 5 Due...

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Electricity and Magnetism I (P331) Homework 5 Due: Thursday , October 15, 4:00 PM 1. (a) Show that the electric field of a pure dipole can be written in a coordinate-free form as E ( r ) = 1 4 π± 0 1 r 3 [3( p · ˆ r r - p ] . (1) (b) Show that the energy of an ideal dipole p in an electric field E is given by U = - p · E . (2) To do this consider the amount of work done to move a dipole from infinity through an electric field and then orient the dipole in some specific direction with respect to the electric field. (c) Use your answers to (a) and (b) to show that the interaction energy of two dipoles separated by a distance r is U = 1 4 π± 0 1 r 3 [ p 1 · p 2 - 3( p 1 · ˆ r )( p 2 · ˆ r )] . (3) 2. Imagine three charged rods with length ` and charge Q. The rods are arranged so that one end of each rod is at the origin and the other end is a distance ` away from the origin along the x , y , and z axis. (a) Find the dipole moment of this charge charge distribution
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This note was uploaded on 01/20/2012 for the course PHYSICS 331 taught by Professor Staff during the Fall '09 term at Indiana.

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