4 ms·
I think you are missing the point of the water analogies. It is what made electricity make sense to me as well. But don't take it too literally, it's an analogy
by robbrown451 10y ago
I think you are missing the point of the water analogies. It is what made electricity make sense to me as well. But don't take it too literally, it's an analogy, not an identity.
If you start with things like "a motor is like a turbine, a generator is like a pump, a battery is like an elevated tank", a lot of things can fall into place. The point is you can visualize it.
- gohrt 10y agoIt's hardly fair to say that water analogies are good but "capacitors store charge" is bad, they are both weak analogies
- CamperBob2 10y agoThere's nothing weak about saying capacitors store charge. That's exactly what they do. You measure charge in coulombs, which is how you count electrons. Capacitance is just the value that relates stored coulombs of charge to available voltage.
- gugagore 10y agoI didn't agree with what you wrote and maybe I can explain why. Springs store inches. You measure displacement in inches. Spring constant is just the value that relates stored inches to available force. (You can swap roles of force and displacement if you wish, the point is the same. It sounds bad to say springs store force or displacement, to me.)
- CamperBob2 10y agoBut inches are an abstract measurement of distance. Electrons are a thing. (Well, depending on who you ask... no one has ever seen one, and some people have claimed half-jokingly there's only one electron in the entire universe: https://en.wikipedia.org/wiki/One-electron_universe https://en.wikipedia.org/wiki/One-electron_universe .)
- gugagore 10y agoWhat?? Okay then count by lengths of the spacing of carbon molecules in graphite, or Plank lengths, or whatever. I don't see why your objection is on inches or otherwise any unit I chose for dimension of length.
- DigitalJack 10y agoIf you compress a spring, and then heat it, what happens to the stored inches?
- gugagore 10y agoCan you clarify what your point is? I don't know how to answer the question, because springs don't store inches. If you are making a point about why the spring/inches analogy was bad, I'd like to hear it.
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- wbeaty 10y agoSo, you're saying that capacitors store electrons?! Debunking this particular conception was the whole point of my capacitor article http://amasci.com/emotor/cap1.html http://amasci.com/emotor/cap1.html Capacitors "store" electrons, like springs "store" steel, or rubber bands "store" rubber. A charged capacitor has exactly the same number of electrons as an "uncharged" capacitor. When "charging" a capacitor, charge is forced into one terminal, and exactly equal charge comes out of the other terminal. No electrons build up inside, nor are placed into it. They've just been moved around inside, same as the steel spring, or the spherical tank in the water analogy. What then do capacitors store? EXACTLY! That's the questions that students should be asking. They won't think to ask it, if they've been taught that capacitors are like buckets full of electrons. Well, what does a steel spring store? Or a stretched rubber band? KG of steel or rubber? Nope. Capacitors store joules, not coulombs. The above concepts open the way to unifying several ideas: capacitors store charge in the same way that inductors store charge! In both components, energy is stored, as e-fields in the case of capacitors, b-fields in the case of conductors.
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