When using extensions cords I find that I feel like there is similar amount of electricity going through it as just plugging a cable into the wall without using an extension cable. When I charge my phone I get similar speeds using either, but surely an extension cord spilts the voltage?
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No, it doesn’t split the voltage. It really is just what the name says, an extension. It’s the same as if your phone charger prongs were 10 feet long, but flexible.
Split the voltage? The extension cord is not a transformer so it doesn’t change the voltage or amperage. It just transfers the power over additional distance.
If you’re talking about an extension cord that has multiple outlets or a power strip, the power supplied which is actually the *wattage* isn’t exactly split between the outlets all the time.
Say your phone charger uses a 20 Watts charger. Your outlet (in the U.S. at least) is capable of putting out 120 Volts at 10 Amps which is 1,200 W. The outlet as a whole has more than enough power or charge multiple devices, not just whatever two you might happen to plug directly into the outlet. This is why power strips work. You just can’t exceed the total for the wall outlet. Not a certain amount per power strip or extension outlet.
Also electrical power doesn’t diminish over distance with wiring. Not in any appreciable way for the consumer home use. Wireless charging has distance limits due to the extra middle man of magnetic fields for which do diminish in power rapidly with distance. But that’s another topic. Look up “magnetic induction.”
It gets a little complicated because the above example is sort of presuming you have only a single outlet on a circuit. Also ignoring heat build up, but for ELI5 purposes, it’ll do.
The outlets in your home’s walls are connected via wires that run through conduits to the breaker box/power panel in your home, and are connected through that point to the power lines that feed your home.
When you plug in an extension cord, you’re just adding more length to the wires that run to your power outlet, extending the reach so you can connect other things that may not be able to easily reach the outlet.
If you are plugging multiple things into an extension cord, it does not split the voltage, but it does increase the load on the wires bringing the electrical current, which is why you should avoid overloading extension cords or plugging too many items into a single outlet.
There is a small drop in voltage across an extension cable. No common cable is a perfect conductor, they always have some resistance, and that resistance will increase as length increases, wasting power. But it’s not nearly enough to affect something like the charging speed of a phone unless you measure it very carefully. Not for any cable you can buy somewhere you’d actually be shopping.
The primary threat of extension cords, if anything, is simply that they can be tripped over. Or, if you live in the United States in particular, that [not all of them may be built to safely withstand the maximum current of your wall sockets](https://www.youtube.com/watch?v=K_q-xnYRugQ). The latter could (in theory) cause it to overheat and cause a fire without triggering safety mechanisms.
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