Just wondering cus like wouldn’t it be more convenient to just plug your phone into the wall without a brick, or like cheaper to build a pc without a power supply? why do these devices need DC but lamps, fridges, fans, most household appliances can run off AC?
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AC power is alternate current, between either +230v and -230v or +120v and -120v, 50 or 60 times a second. This works really well for some things, such as electric motors, which have the coils charge up to +230v then switch to -230v, which causes the motor to spin. This means it’s super efficient and doesn’t need to be converted when it’s getting used in a fan, the motor in your fridge, motor in your washing machine etc. When you think back to when the power grid was created 100+ years ago, that’s what most devices did.
Things with complex modern circuits like your phone don’t like that constant change in voltage. They’re working with binary, a 1 is typically 3v, and a 0 is 0v, so using alternating current would make things really hard to deal with. This sort of tech is only really from the last 30-40 years or so, so quite a bit newer than the power grid.
The power grid also suffers from voltage drop. When the power lines are long, or the grid is under heavy load, the voltage can change a bit (usually by around 5% either way). For the motor in your washing machine, it doesn’t really matter, but for complex electronics it does, so it makes sense to keep the grid still working for those basic older things, and then convert it into to lower voltage DC (Direct Current) closer to the device. This is why the cable from the wall charger to your device is usually quite short, to reduce the amount of voltage drop once you’re dealing with those smaller, easier to manage voltages.
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