M M Taddei et al 2009 Eur. J. Phys. 30 965 doi:10.1088/0143-0807/30/5/005
M M Taddei1, T N C Mendes2 and C Farina1
Show affiliationsIn this pedagogical work, we point out a subtle mistake that can be made by undergraduate or graduate students in the computation of the electrostatic energy of a system containing charges and perfect conductors if they naively use the image method. Specifically, we show that naive expressions for the electrostatic energy for these systems obtained directly from the image method are wrong by a factor of 1/2. We start our discussion with well-known examples, namely point charge–perfectly conducting wall and point charge–perfectly conducting sphere, and then proceed to the demonstration of general results, valid for conductors of arbitrary shapes.
01.50.My Demonstration experiments and apparatus
41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems
Issue 5 (September 2009)
Received 26 March 2009, in final form 10 June 2009
Published 8 July 2009
M M Taddei et al 2009 Eur. J. Phys. 30 965
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