Length Contraction of Electrons

[member 529879]

If you have a still wire with electrons moving through it, to an outside observer at rest relative to the wire, would the space between the electrons contract? I would think that special relativity causes the electrons to contract, (not the space between them) but the contracting of the electrons would cause the electrons to come closer together.

 

[Nugatory]

Electrons are point particles whose length is zero, so there's nothing to contract. The way to get the electrons to move closer together is for you, the observer, to be in motion relative to the wire; that will contract the length between them.

 

[A.T.]

Electrons are point particles whose length is zero, so there's nothing to contract.

They have electric fields, which are contracted when the electron moves.

The way to get the electrons to move closer together is for you, the observer, to be in motion relative to the wire; that will contract the length between them.

Which would increase their mutual repulsion, if the electrons (their E-fields) weren't contracted as well.

 

[member 529879]

Exactly, and if the repulsions between the electrons contract, wouldn't that allow them to become closer together?

 

[Doug Huffman]

Electron drift velocity (q.v.) in wire is on the order of millimeters per second.

 

[A.T.]

Exactly, and if the repulsions between the electrons contract, wouldn't that allow them to become closer together?

It allows them to be closer together in the observers frame than in the electrons frame, while the repulsive force is the same.

the contracting of the electrons would cause the electrons to come closer together.

That's a misleading way to put it. Contracted repulsive fields are still repulsive, and don't bring anything together.

 

[Nugatory]

Electron drift velocity (q.v.) in wire is on the order of millimeters per second.

That is true, which makes it all the more remarkable that the effects of the tiny relativistic length contraction of the distance between them is sufficient to explain the appearance of magnetic effects. See, for example, http://physics.weber.edu/schroeder/mrr/MRRhandout.pdf