Open and Closed Case

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I know I’m gonna get some eye rolling here but it needs to be said.

When we teach electricity to new techs we use a lot of “water” metaphors. We talk about volts like PSI, amps like flow and Watts like GPM. Even the word “flow” gives us a vision of water moving.

Then we talk switches and circuits and we say “open” to mean no path / no flow and “closed” to mean a path or flow.
That’s the opposite of water…

With water, we “open” the tap when we want flow and close it to stop the flow.
With a switch, we “close” when we make a circuit and we “open” when we break a circuit.

Someone pointed out to me that describing an “open” switch or circuit like a drawbridge may be better. Cars (electrons) can move when the bridge is closed and cannot move when the bridge is open.

It struck me that this water metaphor may be one reason newbies struggle to grasp relays.
Or maybe I’m just overthinking it.

— Bryan


  1. Avatar Chris Stephens says:

    Never thought about it that way, I too was taught basic electrical that way!

  2. Avatar Tim Haley says:

    Good point Bryan. I’m sure that does confuse some techs. When it is fully explained and white boarded, most will get it.

    1. Avatar Bryan Orr says:

      They get it eventually. I just realized that the way I was explaining may have been making it more difficult than it needed to be.

  3. Avatar Freddy Castro says:

    Nah you ain’t overthinking it. That’s small basic information that confused me the first time talked I was talked to about switches until it was explained to me.
    Something small but very helpful to know.

  4. Avatar Chris hiraga says:

    The new breed of tech who goes to school for this should take an electronics course so they can learn gate logic and circuit logic. Especially if they want the big money of commercial/industrial work in the era of green tech.

    I don’t agree with the water metaphor. Real service techs need to learn what a circuit is. If they can’t get it then there is always install.

    1. Avatar Bryan Orr says:

      Hmmm. We have a trade that already has a shortage of techs. I wish everyone had an “engineers mind” but we also need to be practical about it.

      1. Avatar Chris hiraga says:

        We have a trade where half to most mechanical problems are caused by techs who learn by blowing something up. That needs to change.

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