Relativistic Electrodynamics assert that a current carrying wire being neutral in a laboratory frame of reference appears electrostatically charged to an observer in relative motion to that wire (“Relativistic Wire”), like an ordinary pre-charged wire would appear at rest. The theory of this apparent charge of a Relativistic Wire is covered by most textbooks dealing with Relativistic Electrodynamics.Look here:

{http://chip-architect.com/physics/Magnetism_from_ElectroStatics_and_SR.pdf} by Hans de Vries.

Experimental evidence

Experimentally such charge has indirectly been inferred from the electrostatic potential around a Relativistic Wire. My opinion however is that for a doubtless proof of such fundamental theory it would be justified to require more credible and immediate experimental evidence of the postulated nonzero charge of a “Relativistic Wire”.

Proposed Experiment

Missing evidence could preferentially be obtained by means of a sliding “galvanic” contact acting as a probe* to directly pick up the electrostatic potential of a “Relativistic Wire” and adequately store the collected charge as a measure of its potential. Subsequently, the sliding contact and the probe would have to be disconnected in motion, stopped and the conserved charge be measured. A nonzero collected charge could already be regarded as indisputable proof of a nonzero charge of the wire.


Does anybody know if the proposed experiment has ever been done? Your comments will be welcomed.

  • To avoid disturbing homopolar induction in the vacuum field around the wire the probe should be magnetically isolated.
  • $\begingroup$ Your galvanic probe is moving at relativistic speed and in contact with the conducting portion of the wire? $\endgroup$ – BMS Mar 30 '14 at 14:29
  • $\begingroup$ @BMS: Though observer moves with same speed relative to the charge in the conductor, even then won't conductor remain neutral? If observer moves with same speed, it mean no charge is moving, as like conductor which is not carrying current, it should also be neutral. $\endgroup$ – Immortal Player Mar 30 '14 at 17:00

Let the probe move with v <<c, i.e. sub-relativistic thus only first-order in v effect relevant. Order of magnitude of v may be the drifting speed of conduction electrons.


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