A Simple Demonstration of Flux

Hey geeks! Sorry for the recent dearth of blogs. I’ve been scrambling to get SMBC Book 2 prepped, and it’s sucked away most of my discretionary time. But, I’m starting to near the end of that.

So, with that…

A Simple Demonstration of Flux:

While walking today, I was trying to think of a simple way to explain a somewhat counterintuitive quality of flux to a kid. You may remember from your days in college this idea: If you have flux (given by, let’s say, F) coming out of a certain point, and you imagine concentric circles around that point, the flux on the surface of all of those circles will always be F. This is one of those things that is counterintuitive at first (your brain might be saying “bigger circle have bigger flux!!!”) but once you think about it a bit, it makes sense. If it weren’t true, you’d violate conservation.

Here’s the demonstration I came up with:

Take a hose and find something cone-shaped. Preferably, it should be a wide cone, but technically any cone will do.

Cut off the tip of the cone and put the hose through the hole (insert sex joke). Turn on the house so that the water cascades (FLUXES!) down the sides of the cone.

Now, get a bunch of cylinders which have the same volume but different radii. So, maybe a couple different sizes of vegetable cans or flower puts or piping would do it. You can adjust the height to get all the volumes the same.

If the flux is the same at any distance, when you encircle the cone’s tip with the cylinder, each cylinder should fill up as fast as each other cylinder.

Neat, right?

You could even “tune” the hose (or the cylinders) so that each filled up in a particular amount of time. This might lead to really cool stuff. For example, if you calibrated each cylinder to be 5 seconds, you could time 30 seconds by fitting 6 cylinders within each other on top of the cone.

Hmm… I wonder if that idea could be used for a logic puzzle…

Happy geeking! <3,



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3 Responses to A Simple Demonstration of Flux

  1. Your edutainmusement(tm) is profound :)

  2. Cosmo_Steve says:

    Maybe I’ve been doing physics to long but your setup does not seem counter-intuitive to me. I’m a little worried that some day some undergrad is going to try to prove Faraday’s law wrong by quoting the weinerworks.

  3. Eric says:

    Uh… I know you dislike the visual medium but… really, you don’t want to sketch us a picture?

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