You’ll get a charge out of this…

by Stephanie Chasteen on February 8, 2008

401px-drinkingstraws.jpgThis is a great little activity from Eric Muller’s While You’re Waiting for the Food to Come.

Get a plastic drinking straw, in its wrapper. Unwrap one end, so the straw is still wrapped in the paper, and then slide the wrapper quickly up and down over the straw, until the straw and wrapper feel a little warm.

Take off the wrapper and the straw will stick to the palm of your hand!

For extra fun, do this with a friend. Ask them first if they’re attracted to you or repulsed by you! Then both do the straw-thing, and hold the straws near one another (you’ll find that your friend is repulsed by you).

You can find a writeup of this activity on Eric Muller’s website.

Why does this work? The straw ends up negatively charged (it’s got just about 40 nanocoulombs of charge) after being rubbed with the paper. Since like charges repel, it will repel the other straw. And charged objects attract neutral objects, so it sticks to your hand.

This is the same principle as the old rub-the-balloon-on-your-head-and-stick-it-to-the-wall trick.

Here is a simulation you can play with that shows you the physics of this sort of trick.

{ 2 comments… read them below or add one }

edl1680 March 12, 2008 at 4:22 pm

I wish I was back in school so I could learn about all these neat principles by doing the experiments.

sciencegeekgirl March 12, 2008 at 4:35 pm

But that’s the great thing — if you’re not in school you can do whatever experiments you like instead of waiting for a teacher to do them! Science is a way of looking at the world rather than something you can only do in a classroom. I highly recommend Eric’s book (mentioned in that post) if you want to find more of these fun things to do. The Exploratorium also has a new book, Exploratopia, which has a ton of hands-on activities geared at kids but that all of us can enjoy. More about Exploratopia and some sample activities here:

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