Replies

1. 
   PaulBinCT | Jun 22, 2004 12:52am | #1

   You're both right.  The coiling makes it more difficult for the heat to dissipate and the coil does form a winding which can when the power is turned off (in very rare circumstances) create a pulse which can damage circuits... same principle that a coil in a car worked on... But I think they're both pretty extreme and unlikely situations.

2. 
   Sphere | Jun 22, 2004 12:53am | #2

   ask any python..they'll tell ya

    

   Spheramid Enterprises Architectural Woodworks

   Repairs, Remodeling, Restorations. 

1. 
   Treetalk | Jun 22, 2004 02:16am | #3

   Answered a call to look why my neighbors freezer had popped the breaker.Looked in the back room and saw he had made a "temp" ext. cord out of a whole roll of 12/2 wG ! Just pulled both ends out and put plugs on them. The whole roll had melted together into a copper fused blob! "Guess i shouldnt of done that?"

   "Yep!"

3. 
   Jamie_Buxton | Jun 22, 2004 03:20am | #4

   You're running AC current in this coil.  The current in the hot is equal to and opposite in direction to the current in the neutral, and the magnetic fields cancel each other out.

4. 
   DanH | Jun 22, 2004 04:10am | #5

   When an extension cord is coiled, it can't dissipate heat as well. That said, even if the cord is coiled when it melts, it was being overloaded.

   There is no significant magnetic field from a coiled cord, nor is there a significant loss due to magnetic effects. Since the two wires with opposing currents are near each other, the magnetic field cancels out.

1. 
   CPopejoy | Jun 22, 2004 06:54am | #6

   And if, by chance, the coil is placed around a ferrous object?

   Cliff

1. 
   SamT | Jun 22, 2004 02:45pm | #7

   An entire roll of romex is pretty extreme!

   To say they "cancel" each other is not quite right. They oppose each other. The magnetic fields are energy and that energy has to be dissapated somewhere as heat. In a run, no problem, when coiled (A whole roll?) the fields are concentrated, and will produce more btus than otherwise. Plus there is less surface area to dissipate that increased heat resulting in the bar-b-qued romex.

   I'll bet the freezer wasn't workin' so good even before the roasting because the coiling really reduced the current available to it. The voltage was also reduced and way out of phase with the current. The poor compressor didn't know what to do 'cuz it wants it's I and E to be in phase.

   SamT

   Arguing with a Breaktimer is like mud-wrestling a pig -- Sooner or later you find out the pig loves it. Andy Engel

1. 
   DanH | Jun 22, 2004 04:13pm | #9

   > To say they "cancel" each other is not quite right. They oppose each

   > other. The magnetic fields are energy and that energy has to be

   > dissapated somewhere as heat.

   Not entirely true, in fact hardly true at all. Magnetic energy is only converted to heat when there is something magnetic it can affect. Otherwise it is converted back to electricity as the cycle reverses.

1. 
   SamT | Jun 22, 2004 07:07pm | #10

   Magnetic energy is only converted to heat when there is something magnetic it can affect.

   Electrons in the copper conductor are effected by magnetic fields. They move. Copper is not a pure %100 conductor, it has some resistance. Electrons moving against resistance creates heat.

   This is called hyteresis loss IIRC. It's been a few moons since I taught this stuff in the navy.

   SamT

   Arguing with a Breaktimer is like mud-wrestling a pig -- Sooner or later you find out the pig loves it. Andy Engel

2. 
   brownbagg | Jun 22, 2004 08:07pm | #11

   just get a bigger cord.

3. 
   DanH | Jun 22, 2004 10:24pm | #12

   The reason that wires heat up due to inductance is because of the increased current due to power factor. The inductance itself causes very little heating -- the heating's 99.9% due to increased current flow from the power factor.

   Copper has essentially no hysteresis -- hysteresis is primarily a property of ferrous materials.

   You can get inductive heating in, eg, a large copper plate that is placed in an alternating magnetic field, but this heating is due to eddy currents in the copper. There are no significant eddy currents in copper wires because any induced current is in line with the existing current flow.

4. 
   SamT | Jun 22, 2004 11:29pm | #13

   Eddy currents, not hysteresis. I tol' ya it's been a while. Hysteresis is purely about magnetism, not currents, sorry.

   SamT

   Arguing with a Breaktimer is like mud-wrestling a pig -- Sooner or later you find out the pig loves it. Andy Engel

5. 
   MisterT | Jun 23, 2004 04:35am | #14

   This is all verry interesting but can you use the copper wire to cook a hot dog?Mr T

   Happiness is a cold wet nose

   Life is is never to busy to stop and pet the Doggies!!

2. 
   DanH | Jun 22, 2004 04:10pm | #8

   > And if, by chance, the coil is placed around a ferrous object?

   Won't make much difference. The bulk of the magnetic field (probably 99%) doesn't get much beyond the outer jacket.