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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TLDR: You have to use AC for power transmission, you have to use DC for electronics otherwise your electronics would work like shit.
AC is great at two things (probably more but whatever) switching voltage between really high and really low (really high for running power around the country, really low for running your water heater) and for making things spin. To make something spin you have to sort of push things around in a circle so you have to kinda push and pull in certain ways just imagine how your hand has to change direction all the time if you want to spin a wheel around.
AC is a spinny push and pull. DC is a constant push.
Electronics like your phone don’t spin, they just need a constant push to get their energy. But our power system and most “old” things spin to do something useful. The things that don’t spin were designed to use the spinny power because that’s what came into the house.
Because AC is so good at making power strong when pushing it out across the country, we need to start with AC. When it gets to your house it is great for running the spinny things, but for the pushy things there needs to be a brick to turn the spinny power into the pushy power.
Making the spinny power into pushy power results in energy loss, so there’s no reason to make devices like your toaster run on pushy power because then you’d have a toaster that makes heat out of pushy power and also a brick that makes heat out of spinny power sitting on your counter next to the toaster.
We could design electronics to work directly off of AC, but it would be like designing a car that required you to keeping smashing the gas pedal and releasing it at a specific rate to keep you going forward. Think how you would push someone on a swing, you gotta push, then relax for a bit, then hit them again at just the right moment.
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.
Generally speaking. If it has a motor or heating element it will run off AC. If it has any sort of logic board it will run off DC, and if it has both. Like in the case of a refrigerator, it will use both and have a AC to DC circuit built in. Reason is logic boards need not just DC but low voltage DC to work.
Electrons move back and forth, in AC wires.
Electrons move in one direction in DC wires.
Both are good, but have many pros and cons to why we use them where we do.
AC can be sent further with more power, less fixes, and less wiring, which just costs less. You can send 3 wires in one direction, and they don’t have to circle back. You can connect each building off of those wires, and if anything we’re to happen with one building, it wouldn’t affect the others with how we set it up.
To do the same thing with DC, it would cost more money overall, and is an extremely wasteful use application. You would have to have more power plants closer to where they deliver to buildings, and much more wiring, which is thick, and expensive to make, install, repair, and maintain.
With AC, you’ll hear different terms used instead of positive and negative. Because it’s not.
Typical AC- HOT, HOT, NEUTRAL.
DC- POSITIVE and NEGATIVE.
(And both can add a GROUND for safety.)
There’s much more to this, but that would take too long to write.
Batteries are only DC.
Alternating current is much easier to transmit long distances with minimal loss, DC needed a large station every mile, it wasn’t economically viable to electrify countries with DC.
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