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") β 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. π€
Explain it to me as if I was five. πΆ
Well, to say "the voltage differential between A and B is positive" is saying exactly the same thing as saying "the voltage differential between B and A is negative".
There is such a thing as voltage differential. And the voltage potential at one electrode can be higher than the other, or the voltage at one can be lower than the other. But given that "voltage" isn't really a thing except in relation to something else, there's kindof no such thing as "negative voltage" or "positive voltage". Just voltage relative to some other electrode.
And if the voltage of one line is higher than the voltage of a reference ("ground"), then the voltage is said to be "positive". If it's lower, it's said to be "negative".
I don't think "negative voltage" is any less a thing than "positive voltage", really, but neither one is really a thing except in relation to a reference. Which is to say you can't connect a single electrode to an instrument and measure the voltage of that single electrode. That would be meaningless to try. You can only measure the voltage of an electrode by connecting your instrument the electrode and a reference.
Hopefully that clears it up.
This really helped visualize it! Thanks! π