Is it similar to the waves on the surface of an ocean, where the particles go 2 steps forward and 1 step back in waves? If so, what makes it do that? Why would that be used instead of DC current?
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Alternating current arises from the rotational motion of a generator. You don’t need to permanently transport electrons to make electricity do work. They return to the source after they’ve gone through the load. AC is used because the voltage can be easily stepped up and down in a simple transformer using magnetic induction to balance power, loss and safety. Changing DC voltage is more a more complex task.
Think of an electrical device as being like a waterwheel on a river. It’s not using up any of the water, it’s just extracting energy from the current.
So we don’t actually *need* the electrons to go anywhere, we just need them to be in motion. If we push all the electrons in a wire forward, an electrical device attached to part of the wire where the millionth electron is located can extract energy from that electron’s movement. If we then switch directions and pull all the electrons in the wire backward, the device can extract energy from that same electron as it’s moving the other way. Then it can extract more energy from that same electron as we push it forward again, and so on.
As for what makes the electrons do that, well, it’s a machine called an “alternator”. Like, we’re generating electricity that way intentionally.
The reason we’re doing that it because it allows the end user to control the electric pressure. If we were only pushing on electrons in the wire and never pulling on them, then a user who opened a channel would receive a steady stream of electrons and have to put them somewhere. But since we’re pushing the electrons in and then pulling them back, the user can attach a device called a “transformer” that gentles their movements: they can turn “electron gets pushed *way* in and then gets pulled *way* out” into “electron gets pushed a *tiny* bit in and then gets pulled a *tiny* bit out”.
Think about a saw moving back and forth to cut through wood. The saw doesn’t go anywhere but it still converts energy to work on the wood. This is similar to how AC brings energy to a device.
AC is useful for working with electromagnets, because when electric fields change quickly they cause stronger magnetic fields, and these magnetic fields can be used to turn objects. Most electric generators use a rotating device to turn mechanical energy into electrical energy.
Also, it is easier to “step down” or “step up” voltage using AC, since it allows us to use a transformer. This means we can start with 1kV and step it up to 100kV, or some other amount, by trading current for voltage through the transformer. It is much harder to change voltage with DC.
When AC travels down long transmission lines, it loses some energy due to current losses. By making the current lower and the voltage higher, we can reduce these current losses over long distances.
Then, when it reaches your neighborhood, the voltage can be stepped back down to 120v for your wall outlet.
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As other people said, electrons are pretty slow.
Also, the electrons don’t actually carry/transfer the energy in the way you think. They don’t have to make it all the way from the generator to the load to “drop off” their energy.
The energy is carried by an electric field, and that field travels along the wire at the speed of light.
AC is used because it’s very easy to convert voltages using an AC transformer. This is really useful for a distribution network.
Imagine you are hanging on a rope with a **jumar** – a ratcheting clamp that only slides **up** a rope. Right next to you is another rope that slowly moves up and down, and stops for long enough to grab a handle on the rope. The rope next to you goes down and stops, so you grab the handle. When the moving rope goes up, it pulls you up, and your jumar on the static line sides up as well. When the moving rope stops, you let go the handle and hang on the static line until the moving rope stops, and you can grab on to move up again. In this way, you ascend the static line, but the moving line is basically in the same place. But you are only going up half the time.
But what if the moving line was actually a loop, so there were two moving lines, one side going up and the other side going down, and then swapping. Then you could swap handles from one side to the other, and you would keep moving up the static line, twice as fast as you were going previously.
These examples are half-wave rectification, and full-wave rectification. The electronic equivalent of a jumar is called a diode, and it only allows current to flow in one direction. Using multiple diodes and a crossover, you can perform full-wave rectification on an AC voltage to convert it to pulsating waves that are all positive. Add a big capacitor, and the pulsing wave output is smoothed to a stable DC current.
If you had three looped ropes all running at different times, you could always grab the fastest upward moving rope, and go even faster – this is three-phase AC supply.
Imagine a loop of string wrapped around a pipe. You can pull it in once direction, and the friction will heat up the pipe, that’s DC, or you can move it back and forth, the effect will be the same, that’s AC. This behaviour depends only on what’s happening where you hold the string. You can just pull on one side or you can alternate where you pull.
The energy transported by current is not stored in the motion of the electrons but in the field they create. So you can make them go back and forth or slowly drift in one direction. The source will make them move in the wire near the source this starts to creates a field, the field propagates along the wire at close to light speed and gets them moving everywhere. If you plug something in the circuit this disturbs how the electrons can move near it. This causes the field to be different. The source then has to do work to keep the field stable. This is how the energy from the source gets whatever you want to power.
Someone else mentioned this, but I’m linking a video anyways
In short, electrons don’t do the work. They aren’t the thing we are using in our field. We are using the electromagnetic field
No electrons are used up, at all
the voltage flips back and forth as the magnet spins beneath the coil The magnet has two poles, and the current flows in opposite directions under the influence of each pole. a variation on the left-hand rule, in a way. Moving the poles (or the wire, same difference) puts any given place in the wire under the influence of opposite poles half the time.
The frequency of the current (its regular rate of reversal) is a function of the rate of the turning of the coil or magnet.
There is energy in the motion of the electrons without regard to which way they are moving. Normally, under one-directional processes like water flow, you would need to put energy back in to make the water flow the other direction, but this does not apply with a/c electricity because the poles are always converting mechanical energy into electricity, without regard to direction of flow. The magnet polarity is the reason. Magnets have two poles and the electrons will move in opposite directions depending on the polarity of the magnet. No requirement for putting energy back in when going the other way, as one might expect. More like a swinging clock pendulum, although not the best analogy.
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