Is there thermographic difference between AC current flowing wire and DC current flowing wire? And thermogramic differences for drift velocities?
Electronic – Thermography difference between AC current wire and DC current wire
acdc
Related Solutions
The voltage is a difference between the electric potentials of two conductors. Hence, to change voltage, only one of the potentials has to change (although both can). In AC power only one of the wires (live/phase) changes it's potential, while the potential of the other one (neutral) remains constant.
In the picture above, the orange horizontal line represents the potential of the neutral line (marked as zero for convenience), while the blue curve shows the constantly changing (in relation to zero) potential of the phase line.
Since in properly constructed power network the neutral wire is maintained at a potential level close to ground potential, there is nearly no voltage between the neutral and the ground. Hence, touching neutral will not cause current to flow through human body into ground.
Live line, however has a potential that rapidly changes from highly positive relative to ground potential, to highly negative. This difference in potentials (voltage) of the conductor you're touching with your hand and the one you're standing on causes a current flowing through you and at typical outlet voltages can be very deadly.
Analog Ground is a reference to a constant potential wire, that all other signals (voltages) relate to. Is is what you name your "0" when measuring other signals. For example, in most battery-powered devices it is the wire connected directly to the negative terminal of the battery. Naming "ground" or "0" is a matter of convenience, however in outlet-powered applications the designations are often separate, since "ground" is electically connected to actual ground.
If wires were 100% reliable and had zero resistance, there would be no difference between the neutral (groundED conductor) and the safety ground (groundING conductor). Neither condition applies, however.
Even if the neutral-grounded and safety-grounding conductors are connected at the breaker panel, a current-drawing appliance some distance from the box may cause significant voltage drop in the neutral-grounded conductor. Having any exposed parts of the device connect to ground using a separate safety-grounding conductor will avoid the voltage on its end of the neutral wire from appearing on its exposed parts.
Additionally, using separate conductors ensures that a variety of single failures may occur without creating an immediately dangerous situation (though a second failure which occurs without the first having been corrected could be immediately dangerous).
If exposed parts of a device are connected to the safety-grounding conductor, and a hot wire within the device accidentally touches those parts, short-circuit currents should trip the breaker.
If the hot wire fails between the breaker panel and device, the device would get no power, but there would be no dangerous voltages anywhere near the device.
If the neutral-grounded wire fails, the neutral wire in the device may be only a few ohms separated from direct hot potential, but no current would flow through it, and no path would exist from it to anything the operator might touch. Exposed parts would still be safely connected to the safety-grounding conductor.
If the safety-grounding wire fails, the device would no longer be protected against the possibility of a hot wire touching the case, but no immediate danger would be created.
If the case were not connected to anything, failure #1 would create an immediate potentially-lethal situation; if it were connected to neutral, failure #3 would create an immediate potentially-lethal situation. With both wires present, however, a single failure will not create immediate danger.
Best Answer
If the wire is not a superconductor, where current is flowing, power is being dissipated as heat. For the DC case you can expect current in the wire to be fairly uniform, and thus a uniform heating of the wire will occur.
For the AC case the current will not flow uniformly throughout the wire at high frequency. Two effects come into play, the skin effect and the proximity effect. Pictured below is the proximity effect. If the current is not flowing uniformly then the energy being dissipated as heat in the wire will also not be uniform.
So yes, I imagine the two cases could look different, but in either case I think heat dissipation by the wire would be difficult to see with thermal imaging equipment. Even then it will be averaged fairly rapidly by conduction in the metal wire and the insulation covering the wire. So the experiment would work in some special cases, but not in most practical cases.