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. 👶
The lowest geographic place in the United States is Badwater Basin in Death Valley. It’s altitude is -282 feet. That’s a negative altitude.
What does that mean? It means that Badwater Basin is below the 0 altitude level, which we have chosen to define as “mean sea level.” We could have chosen a different altitude too be zero, but we didn’t.
If there is a pathway from the sea (at Mean Sea Level) to Badwater Basin, then the water will flow to the basin, because it would have a lower potential energy in the basin.
Voltage is potential difference. It is always the difference in potential between two different points. But like altitude, we often don’t say one of the two points out loud because it’s a common reference level.
A positive charge in a vacuum will gain speed (kinetic energy) moving from a higher potential to a lower potential, because its potential energy goes down. It doesn’t matter whether it’s going from +9V to +5V versus 0V to -4V. The change in potential is the same.