Frostbite Theater

How to Make Your Own Electroscope!

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Opposites Attract and Likes Repel

An electroscope can be used to show that opposite electric charges attract and like electric charges repel.


Joanna and Steve: Just science!

Joanna: Hi! I'm Joanna!

Steve: And I'm Steve!

Joanna: I'm sure you all know that opposite charges attract and like charges repel, but have you ever seen it? If not, we can show you with these things!

Steve: These devices are called electroscopes. They're made from a little clippy thing and two pieces of plastic.

If Joanna and I take our fingers and scrape them against the plastic sheets, electrons will get ripped off of us and they'll pile onto the plastic. If one piece of plastic becomes negative and the other piece of plastic also becomes negative, the two sheets will repel each other... like this!

Joanna: This is a plastic pen. If I put the pen between the plastic sheets, nothing really happens. That's because the plastic is a good insulator. For electricity, that means that the electrons in the pen can't move that easily. The extra electrons on the plastic sheet push on the electrons in the pen. The electrons in the pen try to move, but because they're in an insulator, they can't. Nothing really moves, so nothing really happens.

Steve: This is a nail. If I put the nail between the plastic sheets they jump to it. That's because the nail is made out of metal and metal is a good conductor. For electricity, that means the electrons can move around. So, if I put the nail between the plastic sheets, the extra electrons on the plastic push on the electrons on the nail. The electrons in the nail want to get away and, since they can move, they do.

Keep in mind, though, the nail's a solid and the atoms of a solid don't get to move however they want to. If an atom loses an electron, it becomes positive. So you end up with a positive zone at the tip of the nail and negative on the plastic sheets, and opposite charges attract!


Steve: Electroscope fight!

Joanna: Nobody's winning!
