21 votes

What is Watts, Volts and Amps ?

I never really understood, and any definition I read, I just forget after a while. can someone explain in a way that I won't forget.

the water analogy doesn't help as I get confused between them. also, Watt is the most confusing for me shouldn't it with some unit of time ? like I could say how much water is flowing per second but just saying how much water is flowing without the time wouldn't be very useful, it could be seconds, minutes, hours. yet, the Watt is never written with respect to time, why is that?

20 comments

  1. [4]
    derekiscool
    (edited )
    Link
    A watt does have time! It's equal to 1 Joule per second of energy transfer. That's also why power consumption is often measured in Kilowatt-Hours, rather than just Kilowatts, by electric meters....

    A watt does have time! It's equal to 1 Joule per second of energy transfer. That's also why power consumption is often measured in Kilowatt-Hours, rather than just Kilowatts, by electric meters. 1KWh is equal to 1000 watts of power being used for 1 hour.

    Using the common water analogy you mentioned, the way I like to think of it is that Volts are like the water pressure, amps are the speed (or flow rate) of the water, and watts are the total water moved per second.

    In reality, the only difference is that instead of moving water, we're moving electrons. That's why the water analogy is so effective.

    I suppose this doesn't entirely answer your question, since I'm still using the water analogy, but I genuinely can't think of another way to explain it. I'll ponder for a while, maybe I can think of another analogy with some time.

    14 votes
    1. [2]
      updawg
      Link Parent
      Well, ackshually...

      In reality, the only difference is that instead of moving water, we're moving electrons.

      Well, ackshually...

      9 votes
      1. Baeocystin
        Link Parent
        ...so you want to field this one? :D

        ...so you want to field this one? :D

        6 votes
    2. davek804
      Link Parent
      I wonder if the whole duality of light thing would be useful to bring into the discussion when using the water metaphor to explain electricity? Duality of light: a photon is both a wave and a...

      I wonder if the whole duality of light thing would be useful to bring into the discussion when using the water metaphor to explain electricity?

      Duality of light: a photon is both a wave and a particle. Generally, at least when I was in basic chemistry, we didn't have a way to observe both states at once. You build a form of measure and can see one or the other

      So yeah, mentally, when I think of electricity, I think of it as both a particle and a wave. But I'm just a non-scientific pleb.

  2. kari
    Link
    Power is energy over time and, like @derekiscool said, 1 W = 1 J/s, so it’s just inherently there. Horsepower is also a measure of power, equal to 745.7 W or 745.7 J/s, but you probably never...

    the Watt is never written with respect to time, why is that?

    Power is energy over time and, like @derekiscool said, 1 W = 1 J/s, so it’s just inherently there. Horsepower is also a measure of power, equal to 745.7 W or 745.7 J/s, but you probably never question why cars aren’t rated in “hp/second” or something like that. It’s the same idea.

    6 votes
  3. [5]
    Barney
    Link
    I'm going to try a different analogy, maybe that helps you a bit! You asked about 3 things, watts (power), amps (electric current) and volts (electric potential). Current (amps) I'll start with...

    I'm going to try a different analogy, maybe that helps you a bit!

    You asked about 3 things, watts (power), amps (electric current) and volts (electric potential).

    Current (amps)

    I'll start with current, since that's the easiest. I'm going to operate under the assumption that you know what electrons are. Current is how many electrons flow / go in a particular direction. Amps is the international unit we use today, but it could be anything, really. It's some factor of "number of electrons / second" going in this direction.

    Voltage (volts)

    Imagine having a ball on a flat surface. If you just leave the ball there, nothing happens. That's 0 volts, or 0 electric potential. Now if you imagine a hill, if you put a ball anywhere on the slope, that ball will want to roll downhill. By doing some work yourself, you can roll the ball uphill, but it will want to roll downhill normally, and you need to work against that. The steeper the hill, the higher the voltage. You can imagine electric potential like that too, just for electrons and wires instead of a ball and a hill. The wall outlet is generally 230V (or 110V if you're in the US), which is just a metric for "how strong the electrons want to come out of there". This isn't perfectly accurate, but I hope it gets the idea across.

    Power (watts)

    This is pretty simple too. It's how much work the given thing is doing per second. A watt is defined as "Joule / second", but it's essentially just "energy / time". A fun little addendum, power is voltage * current, so: watt = volts * amps. :)

    4 votes
    1. [2]
      Sunbutt23
      Link Parent
      We always said in physics class

      We always said in physics class

      Power is Very Important (P=V*I)

      3 votes
      1. kari
        Link Parent
        I always said (to myself) “penis in vagina” => P=IV lmao

        I always said (to myself) “penis in vagina” => P=IV lmao

        1 vote
    2. kari
      Link Parent
      Hey, we’re 120V. There’s also Japan where it’s 100V and, depending whether your east or west of Tokyo, can have different frequencies (50Hz in half the country, 60Hz in the other half)

      The wall outlet is generally 230V (or 110V if you're in the US)

      Hey, we’re 120V. There’s also Japan where it’s 100V and, depending whether your east or west of Tokyo, can have different frequencies (50Hz in half the country, 60Hz in the other half)

    3. sparksbet
      Link Parent
      I appreciate not being strictly US-centric here, but given that this site is based in Canada, it would probably be better to say "North America (and a couple other exceptions)". It would also be...

      The wall outlet is generally 230V (or 110V if you're in the US)

      I appreciate not being strictly US-centric here, but given that this site is based in Canada, it would probably be better to say "North America (and a couple other exceptions)". It would also be more accurate (and less Eurocentric) to say 220-240V rather than 230V, since you do cover most of the world with that range but not necessarily with 230V specifically.

  4. [2]
    skybrian
    Link
    Watts tell you energy consumption. For example, a light bulb consumes a steady amount of electricity when it’s turned on. A 100 watt light bulb consumes twice as much as a 50 watt bulb, or the...

    Watts tell you energy consumption. For example, a light bulb consumes a steady amount of electricity when it’s turned on. A 100 watt light bulb consumes twice as much as a 50 watt bulb, or the same as two 50 watt bulbs.

    (When connected in parallel, and ignoring things like dimmer switches.)

    As others have said, it’s implicitly per second. You need to multiply by the time that the light bulb is left on to get energy used.

    If you want a water analogy, a bigger pipe will let more water flow through it than a smaller pipe. But you could have two smaller pipes that are equivalent to a bigger one.

    3 votes
    1. kovboydan
      Link Parent
      To explicitly connect this with the 1 J/s parts of comments: 1 W for one second would be 1 J/s x 1 s, the seconds would cancel out, and you’d be left with 1 J.

      As others have said, it’s implicitly per second. You need to multiply by the time that the light bulb is left on to get energy used.

      To explicitly connect this with the 1 J/s parts of comments: 1 W for one second would be 1 J/s x 1 s, the seconds would cancel out, and you’d be left with 1 J.

      5 votes
  5. Englerdy
    (edited )
    Link
    I'll take a stab at something really short and maybe a bit more conceptual*: Watts: How much energy is flowing every second Volts: How strongly motivated electrons are to move Amps: How many...

    I'll take a stab at something really short and maybe a bit more conceptual*:
    Watts: How much energy is flowing every second
    Volts: How strongly motivated electrons are to move
    Amps: How many electrons are flowing every second


    And then some slightly longer explanations maybe:
    Watts is power transfer which comes from the combination of voltage (motivation for electrons to move) and amps (how many electrons are flowing). Watts can also be used for heat flow (how much thermal energy moves every second) which may or may not be helpful for remembering.

    Voltage is often called a potential. You could almost think of it like a rubber band or spring. Without pulling it has zero potential, but as you stretch it, there's increasingly greater potential energy that can be released when you let it go for it to jump back to its unexpanded state. Voltage relates how motivated electrons are move from a high voltage ("stretched out") to a low voltage (a resting state).

    Amps are measuring the individual electrons as they race from a high voltage to a lower voltage (which is electric current). This is the water in the water analogy. But could also be marbles rolling down a hill. It's counting how many run by every second on their way down.

    You didn't mention it, but thinking of resistance also helps intuition. For the rubber band/spring anology, resistance is kind of like the air the rubber band or spring is sitting in. When the spring gets released, air doesn't really resist it snapping back to its original shape. But if you held the spring in honey or molasses and stretched it, you'd see it contract more slowly because of it needing to move really thick liquid out of the way. Resistance slows down the rate that electrons move from high voltage to low voltage. So for the same voltage, it affects how quickly electrons flow and as a result, how much energy moves every second.

    *Trying to keep this pretty abstract, I know these aren't especially rigorous explanations.

    2 votes
  6. [3]
    tomf
    Link
    This might help - https://i.imgur.com/yNMWeDv.jpeg
    2 votes
    1. [2]
      0x29A
      Link Parent
      Would it be appropriate then to consider "watts" a measurement of the combined "amount of work being accomplished" by the amp and volt beings (in this image) per second? I was going to say effort,...

      Would it be appropriate then to consider "watts" a measurement of the combined "amount of work being accomplished" by the amp and volt beings (in this image) per second?

      I was going to say effort, but that sounds more like volts, and then I was going to say "the calories the amp and volt beings are expending per second in the image" but then I remembered the whole calories and joules relationship and then the analogies maybe get messy lmao... still fun to try and analogize/visualize these

      1 vote
      1. tomf
        Link Parent
        yeah, I think its fair to say that about watts. Watts is just v*a of all things, I think this always has the best and worst analogies.

        yeah, I think its fair to say that about watts. Watts is just v*a of all things, I think this always has the best and worst analogies.

        1 vote
  7. stu2b50
    Link
    It is. Watts are just j/s. It's just given a name since it's a common unit. This isn't even a particularly electrical unit, it's used everywhere. Volts: imagine if you invented a unit, say, P, and...

    Watt is the most confusing for me shouldn't it with some unit of time

    It is. Watts are just j/s. It's just given a name since it's a common unit. This isn't even a particularly electrical unit, it's used everywhere.

    Volts: imagine if you invented a unit, say, P, and say it's equal to g * h, that is, the gravitational acceleration at a specific field distance * the separation between the two objects. If you were to multiply this P by mass, you'd have energy. E = g * m * h. Similarly, if you multiply volts by coloumbs - that is, charge - you get energy. That's why it's usually called electric potential. IF there was charge, how much energy would there be? Or, per every unit of charge, how much energy is in the electromagnetic field?

    Amps: charge / second. That shouldn't be too hard to intuit. Maybe more useful, think of what is missing. Amps describes how much charge is going in; does that tell you how much energy is in the system? No, because you don't know how much energy each charge has. Charge is like mass in gravity. You don't know how much energy is in a gravitational system when I tell you just the masses. A car floating 100m in the sky has more energy than a car on the ground - that is evident by the fact that car will fall down and explode if it is 100m in the sky. The height and gravitational constant is required to tell you how much each unit of mass has how much energy.

    What tells you how much energy each charge has? Voltage.

    1 vote
  8. kovboydan
    Link
    I refreshed before posting so I’ll only leave this part: A watt is 1 J/s so it “is“ per second. It might help to look at the SI base units and cancel out various units like time (s) to see how V,...

    I refreshed before posting so I’ll only leave this part:

    A watt is 1 J/s so it “is“ per second.

    It might help to look at the SI base units and cancel out various units like time (s) to see how V, A, and W relate.

    1 vote
  9. Akir
    Link
    If I may take the wider perspective, I wonder how long it will be until AI completely supplants this kind of post? I’ve been using Claude to cram quiz questions and explain difficult concepts and...

    If I may take the wider perspective, I wonder how long it will be until AI completely supplants this kind of post? I’ve been using Claude to cram quiz questions and explain difficult concepts and it’s been going pretty well I think. It’s one of those things that is easy to forget that everyone isn’t doing after a while.

    1 vote
  10. kacey
    Link
    May I ask if there's a context in which this came up recently? Perhaps providing an answer in terms of something that you run into frequently would stick in your head better than something to do...

    May I ask if there's a context in which this came up recently? Perhaps providing an answer in terms of something that you run into frequently would stick in your head better than something to do with water?