What Happens When an Uninsulated Wire Coils Around a Metal Object?

[Dorsk81]

So an insulated electrical wire coiled around metal can create an electromagnet, but what happens if the same wire isn't insulated, and simply makes direct contact with the metal object it is coiled around, does the magnetic field shift then as well? Would there be any other side effects besides the object being electrified? If the wire had a higher conductive value than the ferrous metal it attached to, would it conduct greater current (than that metal) down the length of the coil even after making contact?

I have an idea that requires the only insulation be exterior, and not preventing the wire contacting the object, but it would be no good if it magnetized the metal object.

 

[timthereaper]

If you have an uninsulated wire touching a metal object, don't you just get a conductor? It's like cutting a wire and touching both ends to the cylindrical surface of a rod. The current will just pass through the line (roughly) between the points on the rod the wires are touching. It won't pass through the whole rod.

The orientation of the wire in a coil makes the current pass through in a certain way to allow the magnetic fields to add up to make a north and south pole. With this uninsulated configuration, the current won't circle the metal object like a coil (see above), so it won't make the same kind of magnetic field as a coil would. In essence, it would stop functioning like a bar magnet.

If the object were a better conductor than the insulated wire (let's say it's silver or something), it wouldn't make that much difference. There is some resistance in the wire already, but you'd basically be replacing a section of wire equal to the diameter of the object with the better conductor. the difference in resistance would be practically negligible, and thus your current increase would be negligible as well.

 

[Dorsk81]

Ah, true, I wasn't thinking about it in terms of positive and negative attracting/colliding to close the shortest distance. So if I wanted a current to run from one tip of the object to another I'd need to run a positive insulated wire to one end and a negative insulated wire to the other, without coiling around the object?

 

[sophiecentaur]

Ah, true, I wasn't thinking about it in terms of positive and negative attracting/colliding to close the shortest distance. So if I wanted a current to run from one tip of the object to another I'd need to run a positive insulated wire to one end and a negative insulated wire to the other, without coiling around the object?

It really wouldn't make a difference if the wire and the object were perfect conductors.

 

[Dorsk81]

Thank you, then my original hypothesis would be correct and my idea needs no redesign at this stage.

 

[sophiecentaur]

Thank you, then my original hypothesis would be correct and my idea needs no redesign at this stage.

Hang on there. I meant that coiling or not wouldn't make any difference. It would just be one 'big', very short short circuit. The coil would not be relevant.

 

[Dorsk81]

Ah, so the lines would still need to be attached at opposite ends of a cylinder in order for the current to reach both ends relatively evenly, or would it matter so long as nothing was grounding the object?

 

[sophiecentaur]

Draw out the circuit, including all the contacts between coil and object. If the object makes a good contact (s) with the wire then you have a series of short circuits and there will be vanishingly little current flowing around the coil and so the magnetic field will be more or less zero.
These questions are very hard to deal with because they are a mixture of 'ideal' and 'practical' ideas. As far as I am concerned, what you are proposing would be a 'flawed' design and would not function as you might have expected. It's the sort of thing that is hardly worth pursuing, further than to say you have included a short circuit which seriously interferes with the 'intended' function of the coil.
This is why people use insulated wire for winding most coils.

 

[Dorsk81]

I have a rather unusual goal, so the means to that goal are expectedly unusual. I have a design with a steel alloy ungrounded object that could be coated with a substance that is electroluminescent, but I wanted to be sure that simply electrifying the object would be enough to create either an even glow across the surface, or a gradually dissipating glow (not a sharp drop in luminescence) the farther it was from the point of contact, or find out if I needed to change the design so that the circuit would more evenly distribute that current across the object's coating.

Coiling the wire around it just seemed practical and aesthetically pleasing from a design standpoint, but could easily be changed.

 

[AlephZero]

I have a design with a steel alloy ungrounded object that could be coated with a substance that is electroluminescent...
Coiling the wire around it just seemed practical and aesthetically pleasing from a design standpoint, but could easily be changed.

You mean something similar to http://www.lumilor.com/about.html ?

It's a bit more complicated than just painting something and coiling a wire round it...

 

[Dorsk81]

I'm aware, I wired my own apartment 10 years ago and everything still works today without issue, but I am still primarily a designer/artist type, so there are a few gaps in my knowledge base when it comes to the theory of how a new idea could function versus why it would or would not.

Electroluminescent paint is also something I've been waiting about a decade for someone to create and put on the market, sadly Lumilor is not yet available to more than a handful of people, and they don't seem very good about responding to emails, but once one person creates something then someone else is bound to figure it out and sell their own version soon enough.

 

[sophiecentaur]

Luminor's website is not very forthcoming about how they excite their paint. Until there's some proper information about that then I should not pile in and try to make a driver for it.

 

[Dorsk81]

True enough, though sooner or later someone will figure it out, and I'd just like to have a functional basic design I can easily modify when that happens, if their product doesn't live up to expectations. If it functions anything like the way I always pictured it should then I already have dozens of ways I could put it to use myself, even regardless of how high the voltage/amps go in some cases.

 

[Bobbywhy]

On the Luminor website they write "the surface is then connected to an inverter and battery". That in itself is contradictory: an inverter puts out AC and a battery outputs DC. Either they are totally incompetent or they are being deliberately vague about how to apply the electrical power source. Meanwhile, there is no sense in guessing.

Bobbywhy

(Edit)
In order to obtain the best possible answers and information here on Physics Forums it is useful to provide all information available early on in the opening post. It not only brings more useful responses, it also avoids misinterpretations and speculations as to your intended project.

Here find a different supplier of electroluminescent paint, along with detailed electrical technical specifications. Included are the voltages, frequencies required to illuminate the paint.

http://electroluminescence-inc.com/techspec.htm

 

[sophiecentaur]

I'm aware, I wired my own apartment 10 years ago and everything still works today without issue, .

I don't see how that relates to electronics at all. You almost certainly didn't use conducting films when you were wiring your apartment and that's how they make these paints glow. I would imagine that you might have trouble putting together the plant to produce such a film on the surface of your painted object.

@Bobbywhy
That was a useful link you found. A slightly more reliable source of information than the original up-in-the-air (and probably over-priced) site.

 

[Dorsk81]

Thank you Bobby, they do look more promising. I'll be sure to include a good bit more detail next time I have a question.

Wiring my apartment was just an example, I've been tinkering with and learning about electronics of all kinds the whole while, but since I never took courses to learn everything in order instead of everything I needed as I need it then I'm always filling the gaps, the learning process never ends.

 

[timthereaper]

I have a rather unusual goal, so the means to that goal are expectedly unusual.

I know what you mean by this, but sometimes this kind of thinking makes people think the second law of thermodynamics is just a good suggestion. No one's telling you not to question the status quo, but just don't get enamored with an idea that you haven't made work in the real world yet.

I have a design with a steel alloy ungrounded object that could be coated with a substance that is electroluminescent, but I wanted to be sure that simply electrifying the object would be enough to create either an even glow across the surface, or a gradually dissipating glow (not a sharp drop in luminescence) the farther it was from the point of contact, or find out if I needed to change the design so that the circuit would more evenly distribute that current across the object's coating.

I think the big question mark is how the substance (LumiLor or whatever) reacts to electric current. Your limiting factor is not the rod or the method of electric current delivery. If you really want to make this work, I'd run some tests on the paint and see what the light intensity/color/whatever is at different current/voltage/whatever levels. Choose what you like from that and design your apparatus accordingly.

 

[sophiecentaur]

I have a rather unusual goal,

Is it unusual to want to make some electroluminescent paint emit light?
Your suggested method of making it happen is unusual and probably will not work. Why not try (at least for a start) by making the paint glow by the recommended means? The stuff clearly needs a very low (uniform flux of) current to flow through a thin layer from a conductor at the front to a conductor at the back. A transparent conducting surface would clearly be best but I guess you might expect some light to be visible by using a grid of fine wires over the top (a coil of fine wire, perhaps, carefully spaced and in contact with the paint. However, most light would probably be produced in the space, immediately beneath the wires (i.e. invisible from the front unless the wires were of gossamer thickness).
Perhaps you could investigate the possibility of buying sheets of clear plastic with a transparent conducting surface - that would achieve more or less what the manufacturers have.

 

[Dorsk81]

The technology might not exist yet for me to do what I had in mind, but I know plastic absolutely can't work for me, it's all or nothing, but it is also a long term goal. At any rate I have no further questions for this thread until one of the two companies gets back to me, everything is just theory until that happens. Thank you.