I understand the concept of DC, but if electrons are just kind of moving back and forth in one place to produce an electric charge for AC, why do they say it’s necessary to have a path back to ground/ 0V if it’s not “moving” towards ground/ 0V?
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To control where the electrons flow. Without the path back, the electrons will look for a high conductive path to a lower potential, which likely doesn’t exist naturally in the environment in a way that serves the purpose of what you are trying to power.
Just like hanging a swing from a bar with a chain allows the swing to go back and forth through an intentional low point, rather than have you crash into the ground or get stuck in a tree branch.
You don’t need a path to ground. Consider a 3 wire delta system. No grounds or neutral there for current flow, aside from grounds for protection systems of course.
The voltage will oscillate back and forth, and so will the current. But there will also be a net VA power flow in one direction, based on the difference in potential between the wires.
I think your difficulty visualising this is to do with ‘just kind of moving back and forth’. Although the current direction alternates with ac, you still need a complete circuit for current to flow.
If you took a single moment in time snapshot of the circuit behaviour, part way through one half cycle of the ac waveform, it would be little different to a dc circuit with a battery connected one way round. The current would be flowing from hot to neutral.
Then, if you waited half a cycle and took another snapshot, the current would be flowing from neutral to hot. The equivalent of having your dc battery connected the other way round.
Neutral sits at 0V, hot alternates between being more positive than this and more negative than this causing the current flow to reverse direction with each half cycle.
In North America 220V standard home systems are divided into two sections 110V each. For 110V requirements one side of the 220V is used along with the neutral to get 110V.
Neutral is connected to Ground at the junction box. This means that the voltage on the wiring in the house can never rise above 110V for example if there is a lightning srtike on the powerlines.
You don’t need a path to ground. Consider a 3 wire delta system. No grounds or neutral there for current flow, aside from grounds for protection systems of course.
The voltage will oscillate back and forth, and so will the current. But there will also be a net VA power flow in one direction, based on the difference in potential between the wires.
Voltage is measured in relation to a reference. The neutral wire is your reference.
For DC, the voltage stays the same, for AC, the voltage changes from positive to negative in relation to that reference.
There are many types of electricity grids, but the neutral wire is often tied to ground somewhere.
(Edit: For multiphase systems, there is not always a neutral needed as the voltage of one phase if referenced to another phase. This video explains it: https://www.youtube.com/watch?v=zaK_dy-x00w)
An analogy with a bicycle chain. With DC, you’re constantly pedalling in one direction. The top half of the chain is always going forwards, and the bottom half is going backwards.
Now think of someone on a unicycle trying to remain roughly stationary – they do this by constantly pedalling backwards and forwards in little steps, and likewise the chain is constantly jiggling backwards and forwards. That’s AC.
The top and bottom halves of the chain are the hot/line and neutral (or whatever terminology is used depending on your country and set-up). Now think what happens if you cut the bottom half of the chain.
In North America 220V standard home systems are divided into two sections 110V each. For 110V requirements one side of the 220V is used along with the neutral to get 110V.
Neutral is connected to Ground at the junction box. This means that the voltage on the wiring in the house can never rise above 110V for example if there is a lightning srtike on the powerlines.
Voltage is measured in relation to a reference. The neutral wire is your reference.
For DC, the voltage stays the same, for AC, the voltage changes from positive to negative in relation to that reference.
There are many types of electricity grids, but the neutral wire is often tied to ground somewhere.
(Edit: For multiphase systems, there is not always a neutral needed as the voltage of one phase if referenced to another phase. This video explains it: https://www.youtube.com/watch?v=zaK_dy-x00w)
AC doesn’t need a neutral. If you’re using neutral and negative interchangeably, then yes it needs a neutral path.
Technically, electricity doesn’t move by electrons but by electromagnetic waves. They’re just really linked together. It’s a common misconception that they move by electrons. Just think about transformers (two coils separated by a gap), there is a gap there but AC can travel across that gap.
You need a complete path for the electricity to travel.
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