I am reading up on logic circuits, families and levels because it’s fun. I have no formal education in physics, computing or electronics.
For power supplies, sometimes one of the supply rails is referred to as ground (abbreviated “GND”) – positive and negative voltages are relative to the ground. In digital electronics, negative voltages are seldom present, and the ground nearly always is the lowest voltage level. In analog electronics (e.g. an audio power amplifier) the ground can be a voltage level between the most positive and most negative voltage level.
I know from previous reading, that electricity - at least when it comes to direct current, but perhaps even when it comes to AC? - has a way in (“line”?) and a way out (“neutral” or “ground”? - disregarding for a second the fact that ground also carries current in case of a ground fault).
Again, from previous reading, I know that we work computers by either supplying them voltage or not (or in some circuits a higher voltage and a lower voltage). In any case, it’s a choice between one or the other, since that is what we are trying to represent: boolean true or false.
So, what is this “negative voltage”? Is this a figure of speech or can voltage actually have a negative value? The part from the article that I quoted above states in relativistic terms, that “the ground can be a voltage level between the most positive and most negative voltage level” (italic text by me), which makes me assume “yes”. But if voltage is electromotive force, how can it be negative? I amusingly imagine a force “sucking” the current backwards. 🤭
Explain it to me as if I was five. 👶
You take some point of your circuit, call it “ground” and define the voltage there as 0.
If something has a higher voltage than it, than the voltage is positive. If the voltage is lower, than it’s negative.
Also, you are mixing energy distribution names with your voltage references. Your ground wire has the same potential as the actual ground (the stuff made of dirt where your house is built). We usually define it as the ground in circuits that are connected to it, but you’ll be surprised by how unusual it is to connect circuits to it.
The charge moves from higher to lower voltages. In a wire, that means that electrons move from lower to higher voltages. The absolute value of a voltage is meaningless, you will only ever use differences between them.
I will definitely keep in mind, that what we use are the differences in voltages (which even makes sense if one were to use the water pipes metaphor).
So, the only reason we have absolute values in our outlets is for compatibility (to make manufacturers lives easier?) and to have some “wiggle room”?
We don’t use absolute values in out outlets because there are no absolute values for voltage.
The line in your outlet oscillates between positive and negative (sqrt(2)*V) relative to the neutral, where V is the nominal voltage of your place. And because this is symmetric, you can also say that the neutral oscillates on the same range relative to the line.