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Splitpair
Premium Member
join:2000-07-29
Cow Towne

Splitpair to nelamvr6

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to nelamvr6

Re: AC Wiring causes wierd chirping sound

said by nelamvr6:

Why exactly are these wires moving against each other?
Because they are handling rather large loads. The inductive field between the current carrying conductors will cause them to attract or move away from one and another. This movement will make noises.

Wayne

nelamvr6
High-End Headphoniac
Premium Member
join:2000-11-28
New London, CT

nelamvr6

Premium Member

said by Splitpair:
said by nelamvr6:

Why exactly are these wires moving against each other?
Because they are handling rather large loads. The inductive field between the current carrying conductors will cause them to attract or move away from one and another. This movement will make noises.

Wayne
Uh...no.

The wires found in houses are either copper or aluminum, most often copper. The magnetic fields around a conductor are not strong enough to attract either aluminum or copper.

Try and see if you can pick up a penny or an aluminum can with a magnet. Even a really strong magnet will not be able to attract copper or aluminum.

Not to mention that most houses don't have wires in conduits but instead use romex.

jig
join:2001-01-05
Hacienda Heights, CA

jig

Member

its not about attracting inert metal, its a metal carrying a current. regardless, i don't see those generating 9600hz

drjim
MVM
join:2000-06-13
Long Beach, CA

drjim to nelamvr6

MVM

to nelamvr6
Uh...YES
The wires themselves produce the magnetic field, and as long as current is flowing in them, there WILL be a magnetic field surrounding them. You don't normally notice it, because the fields are balanced and in-phase, so there's no magnetic attraction or repulsion. AC induction motors use a rotating magnetic field caused by the current flowing through the stator windings to induce a counter EMF and magnetic field in the rotor, producing the torque that turns the rotor. If you have a large current imbalance in parallel conductors, the field surrounding one wire will be much stronger and possibly out-of-phase, depending on the load, resulting in the conductors moving relative to each other. I've SEEN 0000 conductors carrying AC move around under heavy load when the currents in each phase were highly unbalanced.

nelamvr6
High-End Headphoniac
Premium Member
join:2000-11-28
New London, CT

nelamvr6

Premium Member

said by drjim:

Uh...YES
The wires themselves produce the magnetic field, and as long as current is flowing in them, there WILL be a magnetic field surrounding them. You don't normally notice it, because the fields are balanced and in-phase, so there's no magnetic attraction or repulsion. AC induction motors use a rotating magnetic field caused by the current flowing through the stator windings to induce a counter EMF and magnetic field in the rotor, producing the torque that turns the rotor. If you have a large current imbalance in parallel conductors, the field surrounding one wire will be much stronger and possibly out-of-phase, depending on the load, resulting in the conductors moving relative to each other. I've SEEN 0000 conductors carrying AC move around under heavy load when the currents in each phase were highly unbalanced.
No.

There is a world of difference between wires formed into a coil and wires lying parallel in a straight line.

And we are not talking about 0000 conductors. We are talking about household wiring.

There will be no attraction between the two copper wires in a run of romex. Or at least the attraction will be so slight that there will be no movement between the two.

drjim
MVM
join:2000-06-13
Long Beach, CA

drjim

MVM

I'll give you the points for wires in Romex, but you're just flat wrong about about parallel wires in a flat plane.

nelamvr6
High-End Headphoniac
Premium Member
join:2000-11-28
New London, CT

nelamvr6

Premium Member

said by drjim:

I'll give you the points for wires in Romex, but you're just flat wrong about about parallel wires in a flat plane.
No, I respectfully disagree.

Copper wires work very well as electro-magnets when formed into coils. But there would have to be a very large current passing through a straight length of copper to produce a magnetic field strong enough to attract another straight piece of copper.

Way more current than would be found in a household circuit.

tmaertin
Crash Into Me
Premium Member
join:2002-04-03
North Tonawanda, NY

tmaertin to nelamvr6

Premium Member

to nelamvr6
nelamvr6 - just an FYI - the amount of copper in a penny now is too small to test this. If you have a penny minted pre 1982 this would work. The price of copper increased that year - the US Mint changed the penny to a ratio of 97.5% zinc and 2.5% copper.

as far as the issue at hand, if you find the product on the web link below around the house - someone is messing with you. I cant believe they actually make this:

»www.shomer-tec.com/site/ ··· C99BE7CC

nelamvr6
High-End Headphoniac
Premium Member
join:2000-11-28
New London, CT

1 edit

nelamvr6

Premium Member

said by tmaertin:

nelamvr6 - just an FYI - the amount of copper in a penny now is too small to test this. If you have a penny minted pre 1982 this would work. The price of copper increased that year - the US Mint changed the penny to a ratio of 97.5% zinc and 2.5% copper.

as far as the issue at hand, if you find the product on the web link below around the house - someone is messing with you. I cant believe they actually make this:

»www.shomer-tec.com/site/ ··· C99BE7CC
You know I was already aware of this, I was wondering if anyone would point this out! (The penny's copper content that is, not the device in your link.)

But my point was that copper is extremely difficult to magnetize.

tmaertin
Crash Into Me
Premium Member
join:2002-04-03
North Tonawanda, NY

tmaertin

Premium Member

cmon now...tell the truth...you own the Mind Molester lol!
chuckkk
join:2001-11-10
Warner Robins, GA

chuckkk to nelamvr6

Member

to nelamvr6
Actually, copper wire can move due to heating or repulsion.
30 years ago, I worked in a GE test lab. We had a "High Current" test facility that was able to dump 1000 amps at 1000 volts (3 phase) into a dead short. When testing at high current, parallel copper wires connected to the same phase were repelled with enough force to brake fiberglass tape used to help route the wiring to the device under test. The control room had a large armor glass window on the wall of the test chamber. We had molten copper from the device under test sprayed on the armor glass on more than one occasion. It was found necessary to put a piece of plexiglass in front of the armor glass to protect the glass from pitting. Naturally, the plexiglass sheet would be very much the worse for wear after one test shot. The test generator had a 25 ton spinning assembly, and was powered with a several thousand horsepower motor. The motor was powered directly with the high line voltage feeding the whole city. There was a solid state controller that controlled the motor spinup to prevent the rotor starting currents from being excessive. Oil pressure on the bearings was about 5000 PSI.

Some possible electrical sources of chirps in a home:
Fire Alarm or Burgler Alarm
Oven or the Fridge
Electromic Thermostat
Answering Machine
Clock Radio
Fan in air handler, outside A/C unit, or furnace during starting
Ceiling Fan
Land line electronic phone when the line is checked
Electronic ballast
Lawn sprinkler system timers
Water softener
(To name a few)


nelamvr6
High-End Headphoniac
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join:2000-11-28
New London, CT

nelamvr6

Premium Member

said by chuckkk:

Actually, copper wire can move due to heating or repulsion.
30 years ago, I worked in a GE test lab. We had a "High Current" test facility that was able to dump 1000 amps at 1000 volts (3 phase) into a dead short. When testing at high current, parallel copper wires connected to the same phase were repelled with enough force to brake fiberglass tape used to help route the wiring to the device under test. The control room had a large armor glass window on the wall of the test chamber. We had molten copper from the device under test sprayed on the armor glass on more than one occasion. It was found necessary to put a piece of plexiglass in front of the armor glass to protect the glass from pitting. Naturally, the plexiglass sheet would be very much the worse for wear after one test shot. The test generator had a 25 ton spinning assembly, and was powered with a several thousand horsepower motor. The motor was powered directly with the high line voltage feeding the whole city. There was a solid state controller that controlled the motor spinup to prevent the rotor starting currents from being excessive. Oil pressure on the bearings was about 5000 PSI.

Surely you're not suggesting that this is similar to the usage of romex in a household circuit? 1000 amps is a lot of juice.

Do you feel that there will be movement in the conductors of a romex run in ordinary household wiring?

Splitpair
Premium Member
join:2000-07-29
Cow Towne

Splitpair to nelamvr6

Premium Member

to nelamvr6
said by nelamvr6:

The wires found in houses are either copper or aluminum, most often copper. The magnetic fields around a conductor are not strong enough to attract either aluminum or copper.
Incorrect, totally incorrect. They type of conductor is irrelevant it is the current flowing thru the conductor that is relevant.
Not to mention that most houses don't have wires in conduits but instead use romex.
No so my home is an older structure and it’s wiring is in emt.

Wayne

fireflier
Coffee. . .Need Coffee
Premium Member
join:2001-05-25
Limbo

1 edit

fireflier to nelamvr6

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to nelamvr6
Guess I'll have to respsectfully disagree with you. While I don't believe the sound is caused by the specific wiring issue cited (because it's happened in how many different houses?), parallel copper (or aluminum or steel or silver) wires each carrying current do exhibit an attraction or repulsion whose strength is based on:

Their distance
The current in each conductor
The permeability constant of the medium between them.

You can determine the magnetic force between the conductors with the equation:

F/l=mu0*I1*I2/2pi*D

where mu0 = Pi*4E-7 (for air), I1 is the current in one conductor, I2 is the current in the second conductor, and D is the distance between the two. This equation can be found in virtually any college physics book and demonstrates that magnetic attraction between conductors (both carrying current) in this arrangement has nothing to do with the interaction of a magnetic field to a metal but a magnetic field to another magnetic field as both conductors have their own magnetic field.

If you run the math on two conductors with 10A spaced 1E-3 M (1 millimeter) apart, you will get a field strength of roughly 2E-2 Tesla which is considerably stronger than the Earth's magnetic field strength of 60E-6 T at roughly the strongest point. Given that 12AWG house wiring can accommodate up to 20A, the field strength between the conductors could be higher.

One point that should be noted however: The "hot" and "neutral" conductors in "romex" are carrying currents in opposite directions to one another (yes I realize AC changes direction but the current in the hot and neutral remain opposite) and by the right hand rule, conductors carrying opposing currents cause conductors to repel each other, not attract though it could still impart mechanical stresses on the conductors which *might* make them vibrate under special conditions.

Having said that, if the OP has determined that the frequency of the sound is 9600 Hz, then magnetic coupling is not the issue as it would (if it made any noise at all) be a 60 Hz-sounding hum. The cardboard material separating the insulated conductors in romex would probably also serve to dampen any noises they might make resulting from mechanical vibration.
fireflier

fireflier to Splitpair

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to Splitpair
Mostly correct--it is the current flowing through TWO interacting conductors that is relevant. And yes you are correct, the conductor material (assuming it can conduct) is irrelevant for a situation in which two current carrying conductors interact with one another.