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

[Connonym]

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?

[Kali]

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.

[Connonym]

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:

[Orrex]

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.

[Whoa_Nelly]

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/electric_safety.htm#electrical%20fires

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.

[Oeditpus Rex]

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.

[Esra Star]

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.

[Oeditpus Rex]

6. Dammit

I always sucked at electricity. :blush:

[ChoralScholar]

8. Check your physics book.

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.

[Esra Star]

12. For a given voltage, if you raise the resistance of the

circuit you will decrease the current.

[pokerfan]

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.

[One_Life_To_Give]

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.

[krispos42]

15. But a stove is only 240 volts maximum

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=½I₂

P₁=R₁*(I₁)² and P₂=R₂*(I₂)²


Getting P₁ in terms of I₂ and R₂...


P₁=2*R₂*(½I₂)²

P₁=2*R₂*¼I₂²

P₁=R₂*½I₂²=½R₂*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.

[Common Sense Party]

17. "It was my understanding that there would be no math."

--Chevy Chase as Gerald Ford in SNL debate.

[krispos42]

18. LOL n/t

[Jamastiene]

23. lol

:rofl:

Yeah, the math really isn't necessary in this case. Talk about over thinking a situation. :rofl:

[Inchworm]

26. HeHe

I was reading.. my brain started getting hot to the touch and then saw this.

Thanks!

:yourock:

[Jamastiene]

22. Bullshit.

Resistance causes heat, not current. You got it completely backwards. Take it from someone who knows.

[EstimatedProphet]

28. I thought resistance was futile.

[sasquatch]

13. *DING DING DING DING DING DING*

:thumbsup:

[cobalt1999]

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.

[lildreamer316]

9. UNPLUG THEM NOW.

NOT KIDDING.

Serious fire hazard.

Now now now.

Luv ya lots....

[hedgehog]

10. I second that notion.

They're not worth burning down the house.

Believe me, they won't get better after a while, either!

[BlooInBloo]

11. That resistance is high.

[GoddessOfGuinness]

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_prev/manufactured/electrical-mh.shtm

[Connonym]

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.

[MissMillie]

21. hot flashes?

I guess the cord is producing less estrogen as it gets older

[One_Life_To_Give]

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.

[halobeam]

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!

[Starbucks Anarchist]

29. That it's happy to see you.

:hide: ;)

[anarch]

30. it means it's time to replace the cord