# Speed of electricity in a tangled wire

Most sources claim that the speed of electricity in a wire (or signal/information speed) is the EM wave propagation speed of the metal.

What about tangled wires? Am I correct in assuming that for the signal to pass a sharp turn in a wire, electrons need to accumulate there to make the "signal pass"? As electrons travel very slowly compared to the EM wave propagation, surely this adds a lot of delay to the signal?

Edit: made some pictures. In the initial moment, when connecting the wire, there's electric field at point 1, but none at points 2 and 3. When electrons accumulate on the first turn, there will be electric field in point 2 and so on. Is this understanding correct? Or is it more to do with EM waves somehow reflecting through the wire and no electron accumulation?

• I am not sure what "sources" you have been using - the velocity of an EM wave in a wire is a function of the dielectric constant of the medium surrounding the wire. From wikipedia "In electrical cables, the velocity factor mainly depends on the insulating material (see table below)." – Floris Jul 19 '16 at 17:30
• The "signal" on a cable is not carried by the electrons but by the fields surrounding the cable. If you want the cable to actually contain the signal, rather than act as an antenna, then the fields have to stay close to it, which requires that the current return path be close (otherwise there will be an extended electromagnetic field). This leads to either twisted pair or coaxial cable designs. Those you can coil up without significant changes in their properties (sharp bends are excluded), but a single wire would only act like an antenna in your scenario. – CuriousOne Jul 19 '16 at 19:10
• Deleted the incorrect statement and made two figures – eimrek Jul 19 '16 at 20:25

You are confusing the drift velocity of the electrons (which is < 1 mm/sec) with their Fermi velocity (which is $1.57\cdot 10^6 ~\rm{m/s}$ for copper) - source. If any "bunching up" of electrons were to happen, it would very quickly resolve itself.