“never plug extension cords into extension cords” is probably the most common piece of electrical related advice I’ve ever heard. But if you have, say, 2 x 2m long extension cords, and you plug one into the other, why is that considered a lot more unsafe than just using a single 4 or 5 meter cord?
Does it just boil down to that extra connection creating another opportunity for the prongs to slip out and cause a spark or short circuit? Or is there something else happening there?
For that matter - why aren’t super long extension cords (50 or more meters) considered unsafe? Does that also just come down to a matter of only having 2 connections versus 4 or more on a daisy chained cord?
Followup stupid question: is whatever causes piggybacked extension cords to be considered unsafe actually that dangerous, or is it the sort of thing that gets parroted around and misconstrued/blown out of proportion? On a scale from “smoking 20 packs of cigarettes a day” to “stubbing your toe on a really heavy piece of furniture”, how dangerous would you subjectively rate daisy chaining extension cords, assuming it was only 1 hop (2 extension cords, no more), and was kept under 5 or 10 metres?
I’m sure there’s probably somebody bashing their head against a wall at these questions, but I’m not trying to be ignorant, I’m just curious. Thank you for tolerating my stupid questions
The longer the cable, the thicker it needs to be to carry the same amount of current without getting hot. This is due to resistance (Wikipedia does a good job with the details). Basically:
20’ cable be long and thick.
10’ cable be short and thin.
10’ + 10’ cables be long and thin.
Long and thin = heat then fire.
That being said, put an LED light bulb at the end, no problem. Put a gaming PC on the end, problem.
I don’t think you’re right about heat. Two cables in series have double the resistance and therefore double the total heat generation, but that heat energy is split between the two cables so each one does not get hotter than if it was the only cable.
Current and Voltage don’t change, but resistance does (between cable types)?
What are you talking about? Current absolutely changes! Your own formula requires I=V/R
My mispeak there was voltage.
Yes, you will have double heat output due to twice the resistance which causes twice the voltage drop and more or less the same current. But this heat output is spread across twice as much wire, so unless the extension cables are coiled together on the ground each will heat up the same amount as a single one would.
These changes are not linear with extension cords, as the gauge variance is less than changes in length. 100% longer doesn’t mean 100% thicker, and there are material differences in the different lengths, too. Also the heat does not just occur in the wire. Whatever is at the end of that cord has to work harder due to the voltage drop, and harder means hotter.