Effects of a Coiled Cable Okay, I've got a little bit of a layman's question here.
We're doing a bit of spring cleaning in our office and we've found a cabinet with boxes upon boxes of stored wires, so naturally, this discussion arose...
Picture a normal, bog-standard wire, with a plastic outer coating. Now, quite often when these wires are stored, they will wrapped up and twisted, to effectively make a coil.
I was just wondering what the effects of this type of storage would have.
What if you had a 15m wire and only used the each end to cover about a single meter (leaving 14m still twisted and wrapped in the middle), what the effect of the electrical current running through this have?
Thanks for helping us settle a mild dispute!
 A: Sorry for necromancing but someone on the internet is wrong.
Nothing major happens with regard to magnetic fields since the cable hold a wire pair carrying equal and opposite current, thus creating two magnetic fields that almost completely cancel each other out.
The most notorious feature of loaded coiled cables is that they potentially generate a lot of heat in a tight space. In most cases it's not an issue, but at high load with little cooling such a coil could be a fire hazard.
A: You are talking about the inductive effects of the coil of wire. Essentially a wrapped up coil of metal with electrons running through it creates a linear magnetic field since moving electrons through a wire creates a redial field and if you approximate the coil to have infinite loops the field becomes liner.
But, this effect would be very, very small for the wires you are talking about since (a) the coils are not very densely packed and (b) not very much current is flowing through them
Here is the wiki on inductors:
http://en.wikipedia.org/wiki/Inductor
The simple relationship between voltage($v$), inductance($L$), and current($i$) is:
$$V(t) = L \frac{di(t)}{dt}$$
One last thing to consider, magnetic field drops off with distance fast (so as you move away from the source it gets really weak). The plastic protective covering around your wires are a relatively similar thickness to the wires themselves and would buffer anything nearby to most the magnetic effects (which would be weak to begin with)
A: A magnetic field will be generated around the coils of wire if you pass a current through them...
A: It depends on a number of factors. If you run DC current through it, you will establish a strong axial, static magnetic field inside the coil (that is, in the region around which the wires are wrapped). Running an AC current through it will generate an oscillating magnetic field (which, by the way, can induce fields in other loops of wire if they're oriented correctly).
@AtomicCharles's suggestion that the field drops off rapidly only holds for single current-carrying wire, but for a coil this is not the case.
See: http://en.wikipedia.org/wiki/Helmholtz_coil for further details.
A: I had  mine site and someone twisted (about one turn per six inches) the active and neutral power cables along a length of about three hundred feet. This twist was enough to trip the thirty amp breaker at the generator. Twist removed, problem solved. I am providing anecdotal evidence that under a substantial load (high wattage) insulated power wires can have an electromagnetic affect over distance.
With AC power you could imagine a perfect situation of twist and loop which could cause a loss of power as heat in a coiled power lead.
In the initial problem I described it is possible that the twist length was just so; to cause that problem.
