solid vs stranded

You need a single strand of insulated wire. typically, it's insulated with paint instead of rubber, in order to make the coils tighter. Also, are you using a DC (e.g. battery) or AC power source, because you'll need AC.

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Original post by capn_midnight Also, are you using a DC (e.g. battery) or AC power source, because you'll need AC.

I believe that's the wrong way around. [grin]

OK. so I'll need AC power. but before I get an AC-AC transformer, it should be possible to create a galvanometer with DC power right? [disputed]

BTW, why is it that stranded wire does not work? I am not educated on electromagnetic theory, so if somebody explains to me I would appreciate it.

Thanks so far though for the quick reply!

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Original post by geekalert OK. so I'll need AC power. but before I get an AC-AC transformer, it should be possible to create a galvanometer with DC power right? [disputed]

An alternating current will create an alternating magnetic field. I don't think that's what you're after, but I could be wrong.

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BTW, why is it that stranded wire does not work? I am not educated on electromagnetic theory, so if somebody explains to me I would appreciate it.

I don't think there is anything wrong with stranded wire itself, but typically it's much thicker and so you won't get so much on your coil. The usual wire for the sort of electromagnet I assume you're building is thin, solid-cored and enamel-insulated as you can wind a very tight coil with it (so, basically what capn_midnight said). How many turns are there on your coil?

You typically wrap an electromagnet with lots of turns of thin wire, because the number of turns affects the magnet's power. You want it thick enough to handle the current you want to feed it, and no more. 42 gauge magnet wire is a common choice. You can't really strand a wire which is that thin.

Stranded wire doesn't work as well because the magnetic field isn't uniform. The magnetic field is perpendicular to the current. In a solid wire, that means it forms a cylindrical surface away from the wire. In a stranded wire, it'll be a very complicated shape because each of the strands has a magnetic field and they're all pointing slightly different directions and thus not reinforcing eachother as much as they could.

Or so I'd guess, anyways.

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Original post by benryves Quote: Original post by capn_midnight Also, are you using a DC (e.g. battery) or AC power source, because you'll need AC. I believe that's the wrong way around. [grin]

...

I thought a magnetic field was created by a change in electrical current, and a DC power source would then only create a magnetic field just as the circuit was closed. There would be current afterwards, but no change in current.

gah, I can't remember.

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Original post by capn_midnight Quote: Original post by benryves Quote: Original post by capn_midnight Also, are you using a DC (e.g. battery) or AC power source, because you'll need AC. I believe that's the wrong way around. [grin] ... I thought a magnetic field was created by a change in electrical current, and a DC power source would then only create a magnetic field just as the circuit was closed. There would be current afterwards, but no change in current. gah, I can't remember.

You're thinking of Faraday's Law and electromotive force (voltage.)

i could only fit 14 turns with the length of wire I cut... that's probably really little. I believe I am using 20 or 22 guage wire.

It's not really a lot, no. An electric guitar pickup, which works backwards but uses the same principle, is typically between 7000 and 9000 turns.

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Original post by benryves Quote: Original post by geekalert OK. so I'll need AC power. but before I get an AC-AC transformer, it should be possible to create a galvanometer with DC power right? [disputed] An alternating current will create an alternating magnetic field. I don't think that's what you're after, but I could be wrong.

And also a changing magnetic flux, which will induce a back emf which will reduce the strength of it...most likely not what you are after.

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Original post by Extrarius Stranded wire doesn't work as well because the magnetic field isn't uniform. The magnetic field is perpendicular to the current. In a solid wire, that means it forms a cylindrical surface away from the wire. In a stranded wire, it'll be a very complicated shape because each of the strands has a magnetic field and they're all pointing slightly different directions and thus not reinforcing eachother as much as they could. Or so I'd guess, anyways.

If that were true, I'd image that the magnetic field would be a whole lot denser than that of a solid wire. Perhaps if the strands are twisted it might make a difference...?

Example:

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Original post by Programmer One [...]If that were true, I'd image that the magnetic field would be a whole lot denser than that of a solid wire.[...]

The same amount of current is flowing through the same amount of space, but instead of one strong field you have many weak ones facing slightly different directions. Because the strength is inversely proportional to distance squared, a few strong fields add better than many small ones.

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[...]Perhaps if the strands are twisted it might make a difference...?[...]

I've never seen a stranded wire that wasn't braided, twisted, or otherwise 'tangled' inside the insulation.

you need more voltage and thin cables.
turn it like 20 times and use 9(+-6) volt.dc
and thinny isolated cables which is possible.
and may be a needle for test it.
more voltage allways makes it strong.
but if you use 220~ volt. this may fire.or rip?
generally 220(standard voltage) did not kill me but i cant prove.
it is also about currency power (a).
ac is using on dynamic systems (i think)
ac will not work on statik magnets (or you can't see) like your's.