IC power-supply pin - Wikipedia
en.wikipedia.org

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. 👶

  • Nibodhika@lemmy.world
    25·
    2 days ago

    Others have already answered, but one thing I think helps a lot in understanding electricity is to think of it as water. Water running through a hose behaves exactly the same as electricity running through a wire.

    The amount of water running through the hose is similar to the amount of electrons running through the wire. We call this current, and measure it in Amperes. Whenever you read amperes think about the flow of material through the medium. Can this value be negative? Sure, it means the current is flowing in the opposite direction.

    If one end of the hose is higher than the other the water will flow from the taller part to the lowest one. Measuring how tall one part of the system is compared to another tells you a what potential difference there is there. We call this Voltage and measure it in Volts. Whenever you read volts think about the potential of movement, if there is a 5 Volt difference between two points in your circuit, connecting a wire between those points will produce a flow, just like how if one reservoir is higher than another connecting a hose between them will move water around. Can this value be negative? Sure, it means the other side has more potential energy.

    If the inside of the hose has a rougher surface water will have more difficulty flowing through there than if it’s smooth. We call this resistance and measure it in Ohms. Whenever you read ohms think about how difficult it is for the current to flow through. Conversely Mhos (OHM spelled backwards) is how easily current flows through the material. Can either of these values be negative? Not usually, but things can behave as if they had a negative resistance, e.g. an amplifier, which in our water analogy is a device that uses a small water flow to control the doors for a larger door, if you have 1 drop per second it let’s put 1L per second on the other side, so it can be seen as something that increased the water flow, therefore negative resistance.

    Now you want to move a wheel with your water, for the water this wheel is seen like a hose that’s harder to move through, so it offers some resistance. If you don’t have enough water flowing it won’t budge. You can move the wheel ba raising the other side of the hose, this increasing the speed the water flows and giving it more energy, or you can do the same by putting more water in the hose thus increasing the current. Therefore we need a unit to measure how easily the water at a given point can move a wheel. We call this Potence and measure it in Watts or VA (Volt-Ampere). Whenever you see Watt think about the amount of energy the el electricity has at that point.

    Lamps have a measure in Watts, because they’re like a wheel that the water will move, and they’re letting you know how much water energy you need to throw at it for it to move, you can use high amperage low voltage, or high voltage low amperage to get to this result. Because both the Voltage on your house, and the resistance of the lamp are fixed values, you can calculate the resulting amperage and wattage.

    I think I went a bit off topic, but I hope this helps clarify some of those concepts.

      • Nibodhika@lemmy.world
        2·
        2 days ago

        Uh, interesting, I had never heard of that before, I’ll definitely give it a read some time.

        I find the water analogy works well even with electronic concepts like diodes (one way valves), capacitors (something like a shishi-odoshi), etc. The only place it fails is when magnetism is involved, like transformers or electromagnets.

        • printf("%s", name);@piefed.blahaj.zoneOPEnglish
          1·
          2 days ago

          MAD respect for the shishi-odoshi reference! 🤣🩵

          Also, once one has grasped the basics, I find it important to loosen up the water analogy, otherwise it will be harder - or at least it was for me - to understand that the effects of electricity that seem instantaneous (lightbulb on/off) are not the electrons moving at the speed of light, but the electric fields expanding and affecting the neighboring electrons. Right?

          • Nibodhika@lemmy.world
            3·
            2 days ago

            Water analogy still applies for that. If the pipes are already full of water if you inject water on one end it almost immediately comes out of the other, even if the water is only being injected at a slow speed. It’s not immediate because the moment you inject water the water in the pipes first compress and that compression travel like a wave much faster than the water.

            The moment the water analogy falls apart is when you depend on magnetism, because electrons moving cause a magnetic field around, but water moving doesn’t generate any field around it, so it can’t imitate an electromagnet or a transformer.