Electrodynamics and Magnetism
Please give me your valuable comments regarding this post which is about a possibly undone experiment in electromagnetism and I request you to come to your own conclusion regarding these. This experiment is viewed both in terms of the effects of magnetic field and in terms of the effects of Lorentz contraction of moving charges and both of them (as for me) arrives at the same conclusion. This post deals with the effect of Lorentz contraction. The other dealing with classical electrodynamics is followed in the other thread.
We all agree with Lorentz contraction of moving bodies with respect to us. So when it comes to a current carrying conductor, we do (we have to) agree with the effect of Lorentz contraction of the conducting electrons in a conductor.
But we know that a stationary charged particle is not attracted (or repelled) away from this conductor.
Now, this is explained by saying (Purcell/Griffiths/Feynman …etc,) – since we are considering an uncharged wire, the conducting wire does not have a net charge in the lab frame, that the positive charge density equals the negative charge density (nullifying this effect of Lorentz contraction). This leave us a question How And why? Since we know that an uncharged wire is electrically neutral we have equal positive and negative charge density, and when the wire conducts, the conducting electrons undergo the effect of Lorentz contraction and still we keep the charge densities equal. So where is the effect of Lorentz contraction? There are of course various other relativistic explanations for this – like charges flowing from/to other part of the circuit to cancel this difference in charge density to loss of simultaneity of the moving electrons between two points -but all of them were in fact neglecting one thing or the other so as to adjust with the experimental results and all are equally controversial.
Hence, the present article believes that there is the effect of Lorentz contraction of the charges in a conducting wire and is this is not nullified due to any charge redistribution. This article explains the possible reason why this effect of Lorentz contraction in the lab frame is not measured.
Now when one consider the Lorentz contraction of moving electrons, the reasons why we won’t be able to measure its effects are due to -1) The electric field caused by this increase in charge density of the electrons is very feeble and the voltage induced in CD due to this increase in electric field is of the order of a few pico-volts (for a few amps of current in AB)..
2) The electric field which acts on the metallic strip CD also acts on the probes of the potentiometer which develops the same potential across it (i.e., the probes of the wire that are equi-distant from the wire AB are at equi -potential and hence the potentiometer reads zero potential
This creates a situation where the voltage developed can’t be measured directly.
Now, this effect of Lorentz contraction in a wire can be proved with the help of the following experiment.
As the figure suggests, AB is a metal wire in which the current carriers are flowing electrons and CD is a tube filled with some electrolyte and on conduction electro-deposition of copper takes place athe the cathode. Here, the current carriers are positive ions.
So, concerning the experiment and according to the rules of relativity, we can say that the electrons in PQ are repelled away by the increased charge density of the conducting electrons in AB and electrons in RS are attracted due to the increased charge density of the moving positive charges and hence a potential develops across PS.
So would there be a potential developed across P-S?
In the adjoining thread, the same situation and the experiment is addressed in terms of “classical electrodynamics” which too arrives at the same conclusion. But that being a lengthy post, thought of posting it as a separate thread. I request readers to come into your own conclusion regarding these.
Many thanks in advance.
Abhilash J Pillai.
Would this possibly undone (Lorentz contraction) experiment be proved right? Watch
- Thread Starter
- 11-12-2010 20:56