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. 👶
When measuring voltage it is important what reference level you have, conventionally electrons flow from positive to negative, so if you switch the probes it’ll be negative, in a larger circuit you choose a way to navigate and you take the sign and calculate, if it’s positive or negative. PCB are not a good way to see it as they usually are constrained by size and they can have multiple layers and hidden paths also alternate is much more complex to work with.
Also be careful around power supplies PCB, they can have large capacitors that can deliver dangerous voltage.
If you want to get into electronics I suggest starting with DC current, much simpler and you can make some nice projects with arduino or other SBC