if electrical extension cords are meant to be used to connect to an outlet farther away then why is it still bad to plug certain things into them Ex: electric heaters, A/C units and so on?
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Extension cords are irrelevant as long as you don’t stack and coil them under full load (which would let them heat up).
Fire hazards mainly occur when power strips without fuses are being overloaded by having too many high power devices plugged into them. Something will burn eventually, and if it isn’t a fuse then it’s going to be the power strip.
An extension cord is not as good as the nmd90 house cabling in your walls because:
A: extension cords are made up many small strands of copper, this is done to be flexible. House wiring is solid copper, 1 large conductor. Flexible enough for install, but that’s it.
B: the flexible wire can generate more heat due to its internal resistance. So it gets hot and if you pull enough current through it, it might not be rated for it and therefore breakdown and arc / fire.
C: extension cords are meant for a slip fit connection at the plug, it’s not as good for conducting vs a properly terminated wire into a screw terminal. Bad connection = more heat, see above comment.
That’s about as ELI5 as I get on it…
This is mainly a US thing, because having 110V means losses to resistace are higher, hence cables getting warmer. The cable inside the wall is solid copper, to handle the current, but the extension cord isn’t. Meaning that many extension cords aren’t rated for the max current an outlet can give.
In Europe and much of the rest of the world, we have 220V, which makes it easy to make all our extension cords rated to 16 A, the maximum a wall outlet can give. This is plenty of power (3,5 kW), and the fuse/breaker will trip before the cable overheats.
If it is correctly rated and fully unwound, there isn’t a problem, unfortunately people don’t understand those requirements and get it wrong which causes issues. Two similar looking cables may have very different thickness of copper inside so can’t carry the same current and wire wrapped around a drum can’t radiate any heat so it just builds up temperature. There is also an electrical phenomenon called induction which is intensified by wrapping the wire on a drum and can make the voltage increase to beyond what the cable can cope with.
It depends on where you are. This is moslty a US issue, because the US has a bit shit electrical safety code.
The breakers in your house are intended to protect the wires inside your wall nothing more nothing less. Which of course means that if you attach an extension chord that can withstand LESS load than the wires in your wall, that extension chord isn’t protected by your house circuit breakers anymore, since you can now overload the extension chord whilst still keeping the wall wires under a safe load.
For some reason it’s perfectly legal in the US to sell extension chords with significantly lower load capability than your wall circuits, and these extension chords could be overloaded and get quite hot without your walls circuit breaker ever tripping.
That’s why it’s generally discouraged in the US to plug very high power devices, like electric heaters or A/C units, into extension chords.
It’s not bad to plug anything into an extension cord, it’s bad to plug anything that draws more power than the extension cord is capable of safely handling. But rather than explaining gauges over length and telling people that heater isn’t safe to plug into a 50 foot, 20 gauge cord, we just say don’t use cords.
The cords that can handle the power over decent lengths tend to be expensive, so a lot of people don’t have them around, and they’ll probably use the same thin cord that was fine for their desk lamp.
An extension cord is not meant to be used with large appliances like electric heaters, A/C units, or stoves because it can’t handle the amount of electricity that those appliances need. When you use an extension cord with a large appliance, it can overheat and start a fire. Extension cords are only meant to be used with small, low-power appliances like lamps or small fans, which don’t need as much electricity to work. It’s important to use the right kind of cord for the appliance you’re using to keep yourself and your home safe.
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