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what does it mean when an electrical cord gets really warm?

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Connonym Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Sep-30-07 09:32 PM
Original message
what does it mean when an electrical cord gets really warm?
The cord for my ipod speaker gets really hot to the touch as does the cord to my daughter's alarm clock. Doesn't matter what outlet they're on, even in different houses. Is this normal for an appliance cord or should I be worried about it?
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Kali Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Sep-30-07 09:36 PM
Response to Original message
1. not good
usually it means whatever you have plugged in is drawing too much juice - those two items don't sound like they would do that - do any other appliances or cords do it?

An exception I have noticed is things that charge batteries - they seem to get warm.
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Connonym Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Oct-01-07 06:42 AM
Response to Reply #1
19. the ipod speaker is also a charger
base for the ipod. Do you suppose that makes a difference? I did unplug them and the alarm clock I'm cool with tossing but the speaker is a Bose and I no longer can afford anything remotely similar to that. Not that it's worth a housefire, it's not. Maybe I should call their customer service.

At any rate, thank you for all who replied. And you math people, thanks for replying in a foreign language :silly:
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Orrex Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Sep-30-07 09:38 PM
Response to Original message
2. It's really close to whatever it's looking for
If it gets "colder, much colder," then it's moving farter away from it.
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Whoa_Nelly Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Sep-30-07 09:41 PM
Response to Original message
3. It means don't use it
Electrical fires can also start when combustibles come into contact with frayed or broken electrical cords or when wires inside the house or inside an electrical cord overheat.
http://www.cwlp.com/electric_division/electric%20safety...

In other words, you may have broken wire filaments inside the cord, especially if those have been bent repeatedly, suach as through winding/unwinding, or don't have a clear contact to the appliance and/or the socket.
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Oeditpus Rex Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Sep-30-07 09:52 PM
Response to Original message
4. There's too much resistance in the cord
The speaker may be drawing a greater amperage than the cord is designed to handle or the cord itself may be damaged. Either way, if the resistance gets high enough, the cord's insulation could melt and possibly start a fire.

Unplug it.

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Esra Star Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Sep-30-07 10:00 PM
Response to Reply #4
5. It's the other way around. The higher the resistance
the less current will flow, for a given emf (voltage).
The less current the less heat.
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Oeditpus Rex Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Sep-30-07 10:02 PM
Response to Reply #5
6. Dammit
I always sucked at electricity. :blush:

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ChoralScholar Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Sep-30-07 10:11 PM
Response to Reply #5
8. Check your physics book.
Edited on Sun Sep-30-07 10:13 PM by ChoralScholar
All electric heating elements are super-high resistance. That's how they work.
-----------------------------------------------------
"Resistance causes the wire to heat up and glow orange, creating infrared radiation that warms the surface of the bread. The losses in power are called Joule heating or P (joule). Those losses are equal to:

P (joule) = RI2

This equation derives from the equations P=VI and V=RI (Ohm's Law)

P is the power (in Watts).
R is the resistance of the wire (in Ohms)
I is the current though the wire (in Amperes)
V is the voltage tension across the wire (in Volts)

From the Joule heating equation, you can see that the heat (P) will be high when electrical resistance (R) is high. The current that flows through the wire has a very high impact on the heat generated, since the power (P) depends on the square of the current (I).

Other appliances that work on the same principle include a hair dryer, an iron, and an electric space heater."


From the SEED Science Center
http://199.6.131.12/qa2/FAQView.cfm?ID=972
--------------------------------------------------------

So, there are two ways to raise a wire temperature - raise the resistance, or raise the current....

in this particular iPod speaker scenario, broken wire filaments would result in more current per remaining filaments, resulting in increased wire temperature.

What you said is technically true, but the current didn't decrease... the appliance drew the same amount of current over a higher resistance (the more filaments that break - the higher aggregate resistance) resulting in increased wire temperature.
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Esra Star Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Sep-30-07 11:25 PM
Response to Reply #8
12. For a given voltage, if you raise the resistance of the
circuit you will decrease the current.
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pokerfan Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Oct-01-07 12:20 AM
Response to Reply #12
14. Remember that power = I^2R
Current squared multiplied by the resistance. Raise the resistance and the current goes down in direct proportion but the I^2R will initially rise before falling off with more resistance.



I suspect that either the appliance is drawing excessive power or that the gauge of the power cable is insufficient.

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One_Life_To_Give Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Oct-01-07 10:15 AM
Response to Reply #12
24. But the cord is not the dominant resistance!
Think of this as a series circuit of two elements. A Cord of less than 0.1 Ohm in series with a 50 Ohm Load. The cord can increse in resistance to several ohms without any meaningful reduction in the current. Whats more if the resistance of the cord is concentrated at a single point such as the wire connection to the plug terminal. There is more than sufficient wattage to cause a fire.
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krispos42 Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Oct-01-07 12:32 AM
Response to Reply #8
15. But a stove is only 240 volts maximum
Edited on Mon Oct-01-07 12:33 AM by krispos42
If you have two heating elements, and one has twice as much resistance as the other one...

R1= 2*R2

then, with constant voltage, I1=I2

P1=R1*(I1)2 and P2=R2*(I2)2


Getting P1 in terms of I2 and R2...


P1=2*R2*(I2)2

P1=2*R2*I22

P1=R2*I22=R2*I22



Now, P2=R2*I22

P2 is therefore twice that of P1

Remember, P1 is the high-resistance element, P2 is the low-resistance one.

In this power equation, P=RI2, when you double the resistance you drop the amperage in half. And half squared is a quarter. So you actually have a net loss of 50%.

Those elements are almost a short circuit, actually. That is why it's a coil, so that the energy released is through a larger area so that the element doesn't have to melt to put the energy out.
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Common Sense Party Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Oct-01-07 01:01 AM
Response to Reply #15
17. "It was my understanding that there would be no math."
--Chevy Chase as Gerald Ford in SNL debate.
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krispos42 Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Oct-01-07 01:13 AM
Response to Reply #17
18. LOL n/t
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Jamastiene Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Oct-01-07 08:38 AM
Response to Reply #17
23. lol
:rofl:

Yeah, the math really isn't necessary in this case. Talk about over thinking a situation. :rofl:
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Inchworm Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Oct-01-07 10:30 AM
Response to Reply #17
26. HeHe
I was reading.. my brain started getting hot to the touch and then saw this.

Thanks!

:yourock:
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Jamastiene Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Oct-01-07 08:31 AM
Response to Reply #5
22. Bullshit.
Resistance causes heat, not current. You got it completely backwards. Take it from someone who knows.
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EstimatedProphet Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Oct-01-07 11:12 AM
Response to Reply #22
28. I thought resistance was futile.
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sasquatch Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Sep-30-07 11:33 PM
Response to Reply #4
13. *DING DING DING DING DING DING*
:thumbsup:
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cobalt1999 Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Sep-30-07 10:05 PM
Response to Original message
7. It means you are buying a new alarm clock and ipod speaker
I'd unplug something like that immediately, especially an appliance like an alarm clock that is in her bedroom and near her when she is sleeping.
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lildreamer316 Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Sep-30-07 10:12 PM
Response to Original message
9. UNPLUG THEM NOW.
NOT KIDDING.

Serious fire hazard.

Now now now.

Luv ya lots....
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hedgehog Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Sep-30-07 11:17 PM
Response to Reply #9
10. I second that notion.
They're not worth burning down the house.

Believe me, they won't get better after a while, either!
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BlooInBloo Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Sep-30-07 11:20 PM
Response to Original message
11. That resistance is high.
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GoddessOfGuinness Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Oct-01-07 12:45 AM
Response to Original message
16. Resistance is futile.
If an electrical cord is warm to the touch, the cord is underrated or defective.

Check out this site: http://www.usfa.dhs.gov/citizens/all_citizens/home_fire...
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Connonym Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Oct-01-07 07:56 AM
Response to Reply #16
20. excellent informative site, thanks!
Thing that really pisses me off is that these two particular devices have had the warm cord problem from the very beginning and I just figured that it was normal for them. It was daughter insisting that it was scary that made me even question it. All I remember from fire prevention is "stop,drop and roll" and Smokey the Bear -- uh and that's from TV. I'm horrible, I know.
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MissMillie Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Oct-01-07 07:58 AM
Response to Original message
21. hot flashes?
I guess the cord is producing less estrogen as it gets older
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One_Life_To_Give Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Oct-01-07 10:25 AM
Response to Original message
25. More than about 5C rise should be concern
Granted the cord "technically" should be rated for 60C minimum. But as a practical matter I don't think most reputable compliance engineers would let a consumer device cord out with more than a couple degrees of temperature rise.

My suspicion is that the device is either faulty or of dubious origin. However without actually performing some measurements/tests in the lab it's not really practical to determine such.
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halobeam Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Oct-01-07 11:08 AM
Response to Original message
27. I wonder about the metal prongs, too...
the metal prongs on my vacuum were so hot when I unplugged it, I couldn't touch it again. I kind of knew if the plastic wrapped cord felt warm, it may not be good, but I never really made a habit out of checking the prongs.


I hate electricity. I guess because I don't understand it, it's my nature to want to understand everything. I just can't find more hours in the day.

Great that you posted this, I bet it'll help some of us, who don't know about these things!
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Starbucks Anarchist Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Oct-01-07 11:15 AM
Response to Original message
29. That it's happy to see you.
:hide: ;)
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anarch Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Oct-01-07 11:20 AM
Response to Original message
30. it means it's time to replace the cord
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