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. 👶
I think there’s a very physical but also intuitive way of thinking about this which eliminates all of the confusion (even with current conventions)
Forget about voltage and let me introduce potential Think about that as a landscape, its height changes and can be mapped in a height map. It corresponds to the „arbitrary energy level“ a particle on which a force may act. Imagine a ball on a curved hill: when ignoring friction and elasticity, the ball has contact with the plane at a singular point and will begin to roll down the hill. That’s what electrons do in a electric field (they rise to the top actually but you may think about current as „virtual“ positive particles which engineers do all the time. The „sea level“ is usually defined as 0V (the potential is also measured in volts)
Now the concept of voltage becomes nothing more than a height difference. In my opinion this beautifully explains concepts like Kirchhoffs voltage law: walk a circle on earths surface and measure your net height change… it’s always 0.
So to finally ( :D ) answer your question: a negative voltage is a negative height change. You just switch the terminals so that charge flows in the opposite direction.
Also current conventions become less confusing, because there is something all scientists and engineers can agree on: a voltage source creates a hill and a valley in its electric potential, the hill is + and the valley -, engineers think about current as virtual positive charge which will move from + to -, scientists will think about it as electrons moving from - to +.
Often times we use earth ground as the source of 0V. Can you end up with differences in potential on different "earth grounds"?
May I just ask, what "virtual" means here? Non native speaker. 🙏
You’re welcome, I’m glad this explanation made sense, I’m also non-native :D
They are like places where electrons could be, you could also call them „electron holes“. If an electron flows through a conductor, it kicks off other electrons bound to atoms taking their place, which then become free electrons, it’s like a chain reaction without the amplification thing. But they aren’t „physical particles with a positive charge“
You could say electrons flow from left to right but you could also say that holes flow from right to left. You may hear an engineer or electrician say that electrons flow from + to -, because it’s just easier to communicate.
Most components like resistors don’t care about current direction anyway. But semiconductors like diodes do, they’ll heat up very quickly if connected in the wrong way.
For most household appliances this is completely irrelevant because the sine potential (and the current flow it causes) change directions every (depending on where you live) 10ms. Yes your phone is semiconductor based, but your phone charger rectifies the outlets AC current into a DC current with a defined direction.