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H. Humbert
SFN Die Hard

USA
4574 Posts

Posted - 06/20/2006 :  10:24:36  Show Profile Send H. Humbert a Private Message
I was wondering if anyone could answer me a few questions about magnets. I've been reading a few layman's articles on the subject, but I can't seem to find the right information to answer my questions.

I know some magnets can be turned on and off using an electric current, but is it also possible to switch the polarity of magnets with a current?

And is it possible to arrange a line of magnets so in one instance they all attract one another, but then with a switch of polarity make it so they all equally repel on another?

Thanks in advance.


"A man is his own easiest dupe, for what he wishes to be true he generally believes to be true." --Demosthenes

"The first principle is that you must not fool yourself - and you are the easiest person to fool." --Richard P. Feynman

"Face facts with dignity." --found inside a fortune cookie

Edited by - H. Humbert on 06/20/2006 10:28:12

beskeptigal
SFN Die Hard

USA
3834 Posts

Posted - 06/20/2006 :  11:48:17   [Permalink]  Show Profile Send beskeptigal a Private Message
This might help regarding magnetized metals.

The current direction does indeed control polarity and can be reversed in electromagnets. If you were to set up a small electromagnet with a battery source of power, reversing the battery reverses the polarity of the magnet.

To make the magnets repel each other, they'd have to have individual sources of electricity and you'd have to reverse every other one.
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HalfMooner
Dingaling

Philippines
15831 Posts

Posted - 06/20/2006 :  14:21:37   [Permalink]  Show Profile Send HalfMooner a Private Message
B. is right. Also, if you want to switch magnetic polarity, it helps to have a core within the wire winding which can easily change its polarity. A typical iron rod will somewhat resist this polarity change due to its crystalline structure. So sometimes iron powder is (was?) used in these cores. (Or, at least that is my old-timey answer. I have no idea about better materials now being used.)


Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive.
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H. Humbert
SFN Die Hard

USA
4574 Posts

Posted - 06/20/2006 :  14:28:23   [Permalink]  Show Profile Send H. Humbert a Private Message
quote:
Originally posted by beskeptigal
To make the magnets repel each other, they'd have to have individual sources of electricity and you'd have to reverse every other one.

Ok, no that's too complex for what I want to do.

Is it possible then to just simply turn the magnets on and off with a current?

Let's say you glued magnets equidistantly along a string, and then hung the string vertically like a windchime. Would there be a way to pass current down the string (for argument's sake just presume string is conductive), so that the magnets all bunched up together, but then fell back apart when the current was cut?


"A man is his own easiest dupe, for what he wishes to be true he generally believes to be true." --Demosthenes

"The first principle is that you must not fool yourself - and you are the easiest person to fool." --Richard P. Feynman

"Face facts with dignity." --found inside a fortune cookie
Edited by - H. Humbert on 06/20/2006 14:28:58
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HalfMooner
Dingaling

Philippines
15831 Posts

Posted - 06/20/2006 :  14:44:04   [Permalink]  Show Profile Send HalfMooner a Private Message
quote:
Originally posted by H. Humbert

quote:
Originally posted by beskeptigal
To make the magnets repel each other, they'd have to have individual sources of electricity and you'd have to reverse every other one.

Ok, no that's too complex for what I want to do.

Is it possible then to just simply turn the magnets on and off with a current?

Let's say you glued magnets equidistantly along a string, and then hung the string vertically like a windchime. Would there be a way to pass current down the string (for argument's sake just presume string is conductive), so that the magnets all bunched up together, but then fell back apart when the current was cut?



Yes, just wire them all the same, north poles up, for instance. (You'd want to use cores that would not remain magnetized after the direct current is shut off.) The north pole of each electromagnet would snap to the south pole of the adjacent electromagnet. It'd be a cool effect.

Is it just my dirty mind, or are you designing a new kind of sex aid, H.H.?

[Edited to add:] I don't know if this is consistent with what you want to create, but you might want to have the magnets slide along on something rigid like a brass wire, rather than a string, as the magnets might otherwise clump up in an unpredictable, ungainly mass.


Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive.
Edited by - HalfMooner on 06/20/2006 14:59:35
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H. Humbert
SFN Die Hard

USA
4574 Posts

Posted - 06/20/2006 :  15:46:18   [Permalink]  Show Profile Send H. Humbert a Private Message
quote:
Originally posted by HalfMooner
Yes, just wire them all the same, north poles up, for instance. (You'd want to use cores that would not remain magnetized after the direct current is shut off.) The north pole of each electromagnet would snap to the south pole of the adjacent electromagnet. It'd be a cool effect.
Excellent. Now, would anyone know where I could get my hands on a few magnets like this? (The kind with the special cores or whatever, that can be turned on and off with a current.) Are there any type of science hobby stores that specialize in providing such unique supplies, batteries, etc.?

quote:
Is it just my dirty mind, or are you designing a new kind of sex aid, H.H.?
It's a secret. But I can modestly say that my idea has the potential to CHANGE THE WORLD FOREVER!



Well, maybe.


"A man is his own easiest dupe, for what he wishes to be true he generally believes to be true." --Demosthenes

"The first principle is that you must not fool yourself - and you are the easiest person to fool." --Richard P. Feynman

"Face facts with dignity." --found inside a fortune cookie
Edited by - H. Humbert on 06/20/2006 15:47:37
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GeeMack
SFN Regular

USA
1093 Posts

Posted - 06/20/2006 :  16:04:37   [Permalink]  Show Profile Send GeeMack a Private Message
quote:
Originally posted by HalfMooner...

Is it just my dirty mind, or are you designing a new kind of sex aid, H.H.?
And here I was thinking H. might be working on a solution to the old Indian Rope Trick. I guess that shows my frame of reference. I won't even ask about HalfMooner's.
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HalfMooner
Dingaling

Philippines
15831 Posts

Posted - 06/20/2006 :  16:24:37   [Permalink]  Show Profile Send HalfMooner a Private Message
You might check your local Radio Shack store. Some of these carry loose electrical and electronic components. Better would be the sort of quality electronics supply store that is rarer, and is frequented by hobbyists and radio hams. These stores vary from location to location.

Or, you could make your own: http://www.ee.surrey.ac.uk/Workshop/advice/coils/index.html


Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive.
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HalfMooner
Dingaling

Philippines
15831 Posts

Posted - 06/20/2006 :  16:27:20   [Permalink]  Show Profile Send HalfMooner a Private Message
quote:
Originally posted by GeeMack

quote:
Originally posted by HalfMooner...

Is it just my dirty mind, or are you designing a new kind of sex aid, H.H.?
And here I was thinking H. might be working on a solution to the old Indian Rope Trick. I guess that shows my frame of reference. I won't even ask about HalfMooner's.


The Indian Rope Trick! The one trick acknowledged by most professional stage magicians as being impossible -- until now! No wonder H.H. wanted to keep his secret.


Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive.
Edited by - HalfMooner on 06/20/2006 16:28:13
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H. Humbert
SFN Die Hard

USA
4574 Posts

Posted - 06/20/2006 :  17:31:01   [Permalink]  Show Profile Send H. Humbert a Private Message
Ok, here was my huge idea.

I've thought on and off some time now about robots. Specifically, how unlike people they look. The big problem is their exterior appearance. Servos and gears tend to be bulky and don't really mimic human muscles all that well.

I tried reading a few articles on muscles so I could just get an idea of how they worked mechanically, how muscle fibers are able to contract and expand. I must admit most of it was beyond me, but it had something to with ions being attracted to one another or something.

Then last night it hit me. Magnets! Stack several magnets a little ways apart inside a flexible sheathing, you know like Chinese fingercuffs. The sheathing would double as an electrical conduit. Send a small current through the sheathing, and the magnets would draw toward one another, contracting the sheathing. Kill the current to relax them. Voila, an artificial muscle fiber!

If such an artificial muscle fiber could be made smaller with nanotechnology, then hundreds of them could be arranged on a robotic skeleton to mimic the shape and power of real muscle tissue.

Then I got an even better idea. What if you arranged the magnets in a grid or lattice pattern inside an electrically-conductive geletin? Zap the gel with a current and the magnets would attract one another, scrunching the material up just like a flexed muscle. This would be ideal because then instead of having to worry about individual fibers, the gel could just be cut into whatever muscle shape you desired. I thought I was really onto something.

Well, I did a Goodle search and fuck it all if somebody else didn't already think of it.
quote:
To make his artificial muscle, Martin mixes very tiny magnetic particles into a liquid silicon polymer that can gel. When he exposes the gel to a magnetic field he generates with electric current, the particles stick together the way steel balls would on a magnet. "If we're to take all of those steel balls and literally embed them into a gel," Martin explains, "and then we were to pull the gel apart, then all the balls would pull apart and they'd now have little gaps between them. Now if we put those balls that are separated in a magnetic field, all the gaps want to close up and that will cause the gel itself to contract. The entire polymer shrinks with a fairly high force" contracting the way a muscle does.
Well, that was my idea nearly exactly, although he just magnetized the metal with a field rather than direct current.

Bah, a whole day wasted.


"A man is his own easiest dupe, for what he wishes to be true he generally believes to be true." --Demosthenes

"The first principle is that you must not fool yourself - and you are the easiest person to fool." --Richard P. Feynman

"Face facts with dignity." --found inside a fortune cookie
Edited by - H. Humbert on 06/20/2006 18:08:03
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beskeptigal
SFN Die Hard

USA
3834 Posts

Posted - 06/20/2006 :  17:59:19   [Permalink]  Show Profile Send beskeptigal a Private Message
I have my doubts HH. Muscles contract and relax but there are very complex pivot and fulcrum arrangements. When I flex my elbow, I contract the biceps, but when I extend it, I don't just relax the biceps, I contract the triceps. And the movements are steady and controlled. You are talking about on and off plus you have to use very strong magnets to actually hold together if say you wanted to lift something. I think the movements would be just as jerky as the ones you are trying to replace.
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HalfMooner
Dingaling

Philippines
15831 Posts

Posted - 06/20/2006 :  17:59:23   [Permalink]  Show Profile Send HalfMooner a Private Message
quote:
Originally posted by H. Humbert

...

Bah, a whole day wasted.



A whole day, all that research down the drain!

Neat idea, really. And it could be your idea of using electromagnets could be the key, rather than the way that other fellow is doing it. But you may need to invest a day or two more on the idea.

Another approach to robotic muscles is "Methanol-Powered Robot Muscles - Bend It Like Bender." Note that these alcohol-powered muscles are 100-times as strong as the human type. That's the kind of power you need for an army of globe-conquering robots.


Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive.
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H. Humbert
SFN Die Hard

USA
4574 Posts

Posted - 06/20/2006 :  18:04:49   [Permalink]  Show Profile Send H. Humbert a Private Message
quote:
Originally posted by HalfMooner

quote:
Originally posted by H. Humbert

Bah, a whole day wasted.



A whole day, all that research down the drain!
What research? I meant I wasted a whole day fantasizing about realistic robot women serving me cocktails around a pool.


"A man is his own easiest dupe, for what he wishes to be true he generally believes to be true." --Demosthenes

"The first principle is that you must not fool yourself - and you are the easiest person to fool." --Richard P. Feynman

"Face facts with dignity." --found inside a fortune cookie
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beskeptigal
SFN Die Hard

USA
3834 Posts

Posted - 06/20/2006 :  18:05:29   [Permalink]  Show Profile Send beskeptigal a Private Message
quote:
Originally posted by H. Humbert

... Now, would anyone know where I could get my hands on a few magnets like this? (The kind with the special cores or whatever, that can be turned on and off with a current.) Are there any type of science hobby stores that specialize in providing such unique supplies, batteries, etc.?


Well HM and you are getting mixed up here between electromagnets and fixed magnets. All you need for electromagnets is to run current through a coil wrapped around a metal object like an iron nail. Fixed magnets come in all strengths but don't turn on and off with current except as noted in the link in my first post. I've never tried to run a current through a magnet to reverse it's polarity but that site made it sound like you could to varying degrees depending on the material.

You can take non-magnetized iron and with a magnet cause it's electrons to line up in a way it becomes a fixed magnet. Natural magnets have the electrons lined up by the Earth's magnetic field when the metal forms.

How to make an electromagnet.
Edited by - beskeptigal on 06/20/2006 18:08:07
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JohnOAS
SFN Regular

Australia
800 Posts

Posted - 06/20/2006 :  18:09:30   [Permalink]  Show Profile  Visit JohnOAS's Homepage Send JohnOAS a Private Message
quote:
Originally posted by GeeMack

quote:
Originally posted by HalfMooner...

Is it just my dirty mind, or are you designing a new kind of sex aid, H.H.?
And here I was thinking H. might be working on a solution to the old Indian Rope Trick. I guess that shows my frame of reference. I won't even ask about HalfMooner's.


I admit, I too was thinking along the lines of "magic trick".

I could think of lots of ways of doing things like you described, but not simply/cheaply. Although it has inspired me to think of getting some magnetic toys and related items for my daughter. The Edmund Scientific site is a good inspiration for stuff of this nature, for those interested.

If it's artificial muscles you're interested in, you may find this Scientific American Article a good read. I found it on the WorldWide Electroactive Polymer Actuators Webhub on the JPL site.

John's just this guy, you know.
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beskeptigal
SFN Die Hard

USA
3834 Posts

Posted - 06/20/2006 :  18:10:05   [Permalink]  Show Profile Send beskeptigal a Private Message
This looks like a fun site for magnet products:

http://www.teachersource.com/catalog/page/Electricity_Magnetism_Engines/Magnet_Products/

I have some neodymium magnets that are incredibly strong. I use then when hunting meteorites.



Edited by - beskeptigal on 06/20/2006 18:11:59
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