Like Wires Attract and Opposites Repel

Yes, likes attract and opposites repel, at least for current carrying wires anyway. We do a couple of experiments to demonstrate this, and also pass a high current though a stranded wire to visualize what happens to the wires in a lightning rod when lightning strikes.

[@rtos]

Excellent demonstration!

[@ElectromagneticVideos]

Thanks! Is so simple but really a fundamental electrical-magnetic interaction.

[@TheBlibo]

Hi from the uk Beautiful demonstration. Why could this not have been shown in school 50 years ago rather than here is a drawing just accept it. It wasn't until I had to jury rig a starter on a large diesel engine that I saw it for my self the motor pulled about 2000 Amps and the cables really did swing

[@ElectromagneticVideos]

Thank you - really appreciate that! Sadly there are so many interesting experiments that could be used in grade school or high school to really make science interesting and yet are not performed, or at least weren't when you or I were in school (sounds like were were in school about the same time). I had always heard stories about starters pulling enough current to make the wires swing. Its so neat to hear from some who has actually seen it. It is such a weak force - but with over 10 time the current I used I can see how the even thicker starter motor wires would move.

[@crj9416]

This is a perfect example of Fleming's left-hand rule for motors.

[@ElectromagneticVideos]

What I sort of like about it is it really keeps things as basic as possible - no coils, cores etc and all you see is the physics at the most fundamental level. Its too bad you need relatively high currents to generate enough force to move even loose wires or it would be a great science-fair experiment for school kids.

[@BTW...]

Another great video. This is using DC though... keep it simple I suppose. You should see what happens when a large power switchboard is tested for high kA proof testing. Where they dump 45kA or perhaps 80kA into a short circuited busbar system. The busbars heat, soften and attract/repel in a dance for a specific time... they either touch each other or ground in a big flash... or pass the mechanical/electrical proof testing, even so as a great hot mess. All copper bars twisted and black. LOL.. good fun to watch. This explains another rating you see on equipment that may intrigue some people - the kA rating. e.g. You may see ceramic fuse cartridges with the blow rating of say 125A and 100kA also appearing. ..or perhaps a domestic Circuit breaker rated at 10A , but also 6,000A But that's another thing to explain.

[@ElectromagneticVideos]

I would be fascinated to see that - from a good safe distance!!!!!! Do you test those things or were you just lucky enough to be able to observe? If you could video that (and even better with a slo-mo camera ) - wow - what a youtube video you would have!!!!

[@RichardBronosky]

Every time I watch one of your videos, I get one step closer to finding an exploit in the simulation. ☮️❤️🌈

[@ElectromagneticVideos]

I'm not sure what sort of exploit your looking for - but there are always new things that people figure out to do with electricity and magnetism!

[@Sctronic209]

Awesome

[@ElectromagneticVideos]

It is neat to see like that!

[@kissingfrogs]

Nice

[@ElectromagneticVideos]

Thanks!

[@retrozmachine1189]

Single wires carrying DC will move under high current too as they attempt to align with the Earth's magnetic field. Normally the stiffness of the wire that can handle sufficient current masks the effect but if the wire is too thin for the load or fine stranded and with soft insulation the effect can be seen. It'd happen with AC too but the line frequency vs wire mass would probably mask the effect. The buildings around here with lightning protection are old quite old and use thick solid copper straps down and into the ground rather than stranded cables. I have seen newer buildings in other areas with 35mm2 or thicker stranded down to the ground stakes.

[@ElectromagneticVideos]

I'm amazed the earths field is strong enough to have a noticeable effect on wires, even with high current. Is there any common situation where you would see it? Would be really neat to observe or demo in an experiment!

[@retrozmachine1189]

@@ElectromagneticVideos The few times I've seen it happen it has been in battery systems with decent, but not excessive, current over the wire. Not the sort of thing that would see the wire start to glow and the insulation go away. The movement was very slight but enough to make me stop and think 'did that wire just move' and see if I could repeat it by turning things off and on again and it did. One example that springs to mind involved a single 2.5 sq mm stranded wire, the sort of wire that can be seen in cables used to wire up the AC electrical supply in a building. It was an unsupported curve of wire, free to move, probably positioned just-so that all factors came together and allowed it to happen. Potentially I'm mistaken and it was magnetostriction at work too.

[@ElectromagneticVideos]

@@retrozmachine1189 How interesting! I doubt it would have been magnetostriction - I thought that was a really small effect. It couldn't possibly have been the fields from two wires interacting? Either way, I would love to have see it happen!

[@retrozmachine1189]

​@@ElectromagneticVideos Really stretching the recollection now but I think the wire was far enough away from the others that it wouldn't have been affected. I've not tried deliberately setting something up to see if I could reproduce it myself and knowing my luck probably couldn't get it to work.

[@ElectromagneticVideos]

@@retrozmachine1189 Well you were lucky enough to see it! I'm intrigued enough to try seeing if I can duplicate it outside (next year when its warmer!) - too much metal and stray fields in the basement workshop to try it inside.

[@Greg_Chase]

A slight paradox is this. Ignoring the E x B (lorentz force), the magnetic field around two wires where current flows in the same direction in both wires - is the same polarity. For example, run current through wire 'A' and use a compass to detect the magnetic field polarity. Then run current through an adjacent wire 'B' in the same direction as wire 'A'. Use a compass to detect magnetic field polarity around wire 'B'. The magnetic field around wire 'A' has the same polarity as the magnetic field around wire 'B' Since "like poles repel', the 'like' magnetic poles around wires 'A' and 'B' seemingly would push them apart. Trying to reconcile 'like magnetic poles repel' with the Lorentz force between the two wires was really interesting when first learning about this behavior. .

[@ElectromagneticVideos]

So assuming I am understanding your point properly (correct me if I am not!) your saying based purely on magnetic fields (ignoring Lorentz force), two wires carrying current in the same direction should repel "because the magnetic fields are the same, right? Think of two wires near each other carrying current going into the screen so the would look like two dots o o (imaging the o's being filled in). Now put a half circle magnetic core around the each wire like this : (o o) . With current flowing the top of the left bracket will be N, the top of the right bracket will be S (and opposite on the bottom of the bracket). So with N on top left near S top right the cores will attract. And this would be consistent with Lorentz force type results. Hope that helps!

[@Greg_Chase]

@@ElectromagneticVideos Actually more a 'lowest energy equilibrium' perspective (thermodynamics) and comparison of the wire magnetic field with the Lorentz Force. 1) watch the compasses around the wire in the yt video "Magnetic Field Around a Current Carrying Wire" 2) if two such wires were placed next to each other with compasses, the compass of wire #1 directly across from the compass of wire #2 *_WOULD POINT IN THE SAME DIRECTION_* and thus the magnetic fields of the wires oppose each other, and forcing "like" magnets together INCREASES THE ENERGY of the system. From Nature's perspective though, because of the Lorentz Force, it appears Nature had the following dialog: "I have two opposing magnetic fields of the wires, and the energy rises if their opposing magnetic fields are forced to come closer to one another. Not good - I am Nature, and I want the lowest energy equilibrium." "But I have the Lorentz Force which forces them together. Trying to KEEP THE WIRES PHYSICALLY SEPARATED requires more energy than forcing the opposing magnetic fields of the wires together. So the lowest-energy equilibrium is to 'let the Lorentz Force win' and just put up with the opposing, 'like' magnetic fields of the two wires being forced together; because that situation is lower energy than what is required to oppose the effort of the Lorentz Force that brings the wires together." "Why on earth an experimenter is forcing me, Nature - to choose between 'opposing like magnetic fields' and 'opposition to the Lorentz Force' is outside my control, but if they're going to force me to choose, I'm Nature - I'm always going to choose the lowest possible energy"

[@ThriftyToolShed]

Excellent video. Thanks for sharing this! I was wondering about the first experiment if the wires repelled were going back and forth due to the DC charger maybe putting out half- wave? Just a thought since it seemed to be showing that. Keep the videos coming ...

[@ElectromagneticVideos]

Glad you liked it! Actually I had a hard time keeping the wires from swinging back and forth at the slightest touch. The force between them is so low the wires have to be quite loose. The swinging is the momentum of the wires keeping them moving after they reached what would be the equilibrium point due to the repulsion - and the rocking back and forth like a pendulum. If I were to wait for 5 minutes the swinging would stop but due to the high current the insulation would be melting off the wires by then. I was able to do the experiment without swinging by using a variac to gradually increase the current though the wires from zero - and then they gradually move apart. But thats not dramatic enough for a video! I did find if I held the wires together with my hands I could feel the pulsing of the unsmoothed DC. In the "lighting rod simulation" end you can see the pulsing from the AC vibrating the individual wire strands before the fuse together.

[@foureyedchick]

So? From an electrical viewpoint, a twin-lead cable cannot be overloaded too much without causing a short, but from a magnetic viewpoint, a twin-lead can be overloaded a bit, because the wires separate a bit .

[@ElectromagneticVideos]

Its mainly a demo of a very basic physics phenomenon. The force is really minimal - had to pass a large current and setup the wires carefully to make the demo work. In most cases other pressures like bends in the wire would easily overpower the repulsion as the plastic insulation melts to cause a short. The practical application is really current going in the same direction in stranded lighting rod cable. Apparently when lighting hits so much current passes that the metal gets soft and the attraction forces pull the strands together and the bundle of strands gets welded together. I have never see a cable where that has happened but would the thrilled to come across a cable like that. We are sure lucky that wires carrying like currents attract or lighting rods wires might fly apart, break, and not work very well.

[@braidondano3564]

Try solid wire, I feel there could be a twist in those stranded wires.

[@braidondano3564]

And then I saw the end of the video

[@ElectromagneticVideos]

There is a twist and you are right - perhaps heating (the high current does warm them) or similar could twist the wires to move them. But the fact that reversing the current though one wire changes the repulsive direction - and AC doesn't change things - demonstrates that it isn't the case. But - your comment is certainly that of an excellent experimenter - its always important to consider the experiment being contaminated by other things!

[@cynic256]

you should test a string of 12 or 14 gauge MC cable to see if it contains the flames and smoke

[@mikezoltan3227]

Do wires hold any electrical charge after they are unplugged? Seems like when I have a bunch of wires together, They always seemed to get tangled in the worst knots. Worse than rope. Could this be because they still have a little juice and are trying to push away?

[@ElectromagneticVideos]

They could potentially have minuscule charge - the amount of charge they could carry depends on voltage and capacitance - and capacitance would be tiny for the lengths of wire you are talking about, and voltages are low. When you notice things like a static charged sweater its typically thousands of volts and even then the force is tiny. The only thing I can think of why wire would be worse than rope is the stiffness of the conductor and maybe the different surface of insulation vs rope. And even with current flowing the forces are tiny - I did hold the repelling wires together with my fingers - I could feel the force but just barely.

[@charly-s]

Only lost time, no practical use. Self presentation, what else?

[@rtos]

This effect is the basis of all electrical use in your home. Utility transformers use electromagnetic induction to distribute power. Motors use the same to create turning torque.