eli5 ac vs dc current and why appliances run on specific ones
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we often compare electricity flowing like water flowing in pipes. for DC, the water is just going in one direction. with AC, it’s going in one direction, then the other direction, and does this many times a second
most things actually need DC. computer processors for example, need DC. that’s what the power supply in it does (convert AC from the wall to DC for your computer parts). alarm clock. old filament lightbulbs used AC directly. some large appliances can have AC induction motors. but electronics specifically are all DC.
and you’ll probably want to know why we have both. to keep it simple, you can’t increase or decrease DC voltage directly. with AC, you can make the voltage higher or lower with a transformer. so now your question is probably why we don’t just have DC in power lines. great question! that’s because high voltages are more efficient for sending power long distances, so we crank the voltage of power lines up to hundreds of thousands of volts. closer to cities they get lowered to tens of thousands of volts, and in a neighborhood, transformers (those round tube things at the top of power poles) step it down to 240 volts, and that’s what goes into your house. computer processors and most electronics use low voltages, like less than 5 volts. but to make sending power across the country more efficient, we step the voltage up really high. but since we have to change the voltage a few times before it gets into your house, using AC makes more sense.
you CAN change DC to AC, but it requires complicated electronics to do it. AC just needs a transformer. in the simplest form, it’s a like a ring of iron with wires wrapped around opposite sides. if you have 50 loops of wire on both sides, the voltage coming out is the same as the voltage going in. if you have 100 loops on the input side, and 50 on the output side, and your input voltage is 10volts, your voltage coming out will be 5 volts. the voltage changes with the difference in turns (loops) of wire on the input/output side. for changing DC voltage, you need a chip that chops the voltage as much as half a million times a second, and uses a tiny inductor (it’s like a type of transformer) to change the voltage, and the chip constantly monitors the output voltage and adjusts the frequency to keep the output smooth and stable. they get converted back to DC through a thing called a rectifier, then it goes through a filtering stage that makes the output DC as smooth as possible. they’re much more complicated than a traditional transformer for AC. since the power changes voltages many times between the power plant and your house, it makes the most sense to use AC since a simple transformer is all you need to change the voltage.
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