When and Where is a Current Electrically Neutral?

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Scientific Paper
Title When and Where is a Current Electrically Neutral?
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Author(s) Thomas E Phipps
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Published 2011
Journal Proceedings of the NPA
Volume 8
No. of pages 2
Pages 449-451

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Many textbooks of electromagnetism give an example in which a current-carrying wire is alleged to be electrically neutral when at rest in the laboratory. They then show that the Lorentz contraction of moving charge, demanded by special relativity theory, causes a bunching of positive charge and a thinning of negative charge in the inertial system co-moving with the conduction electrons, with a resulting charge density imbalance and non-vanishing electric field measurable in that system. By a more careful application of special relativity theory, we show, on the contrary, that the wire cannot be strictly neutral in its rest system. Therefore the textbook calculations are in error.