problem21_77

University Physics with Modern Physics with Mastering Physics (11th Edition)

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Unformatted text preview: 21.77: a)The field is all in the x -direction (the rest cancels). From the + q charges: 1 q 1 q x 1 qx E= Ex = = . 2 2 2 2 2 2 2 40 a + x 40 a + x 40 (a + x 2 )3 2 a +x (Each + q contributes this). From the - 2q : 1 2q 1 2qx 2q 1 2q 2 2 -3 2 Ex = - Etotal = 2 (a + x 2 )3 2 - x 2 = 4 x 2 ((a x + 1) 40 x 40 0 b) Etotal 1 2q 3a 2 1 3qa 2 1 - 2 + - 1 = 4 x 4 , for x >> a.. 40 x 2 2 x 0 1 1 Note that a point charge drops off like 2 and a dipole like 3 . x x 2 - 1). ...
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This document was uploaded on 02/06/2008.

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