ROFL, floating ball valve? Wow, way to make a toilet analogy, random website.
Also, that's a pretty bad and inaccurate way of explaining what a capacitor is. Think of it like a battery, except it generally stores (far) less energy, and its voltage is proportional (by a factor of its capacitance) to the amount of charge it's holding. Capacitors are almost always used in conjunction with a resistor, and almost always to either create a timer (which is pretty cool if you're a math geek), or to to stabilize a voltage (they can soak up noise, at the cost of latency).
Flux is actually defined (and only useful as) the second derivative of the magnetic field vector. You could say that flux is to acceleration as a magnetic field is to position. As it happens, none of those definitions define flux in this way. It's not sufficient to define it as "the amount of stuff coming in or going out of some place," since flux is something you would never quantify conceptually. The classic example of why this is the case is a transformer; there are several very simple ideas that you need to understand before you can work up to the full thing:
1) When there is current flowing through a wire, there's a magnetic field "spinning" (that is, potential energy lines are cylindrical) around the wire.
2) If you wrap the wire in to a coil, the magnetic field will point in one direction out of the coil.
3) If you run AC through the coil, there's flux proportional to the amplitude* of the AC
4) If you "spin" a magnetic field around a wire, the charged particles in that wire become excited, and move (which is the reverse of #1)
OK, now take two coils and link them together. Run AC through one coil, and you'll get AC out the other. Make sense? Good.
If you're following so far, you should be able to answer this question:
Why can't you transform DC current?
[spoiler] There's no flux in the magnetic field within the coil [/spoiler]
Now that you know what flux is, and why capacitors don't have any, you may laugh.
[edit] * By amplitude, I mean the RMS voltage
