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Electricity: Getting a CHARGE Out of It


Today's Snack: Snap! Crackle! Pop! That's what electricity sounds like, when electrical charges collide. Since we're working with charges today, let's have the perfect snack: a nice bowl of Rice Krispies. Pour on the milk and hear those electrons dancing about!






Plastic spoon

Wool cloth

Puffed rice cereal

4" square piece of tissue paper


Lid from a metal (preferably tin) can, clean and dry (take care not to cut yourself)

Fountain pen

Hard rubber comb

Another piece of tissue paper

Ping-pong balls

Blown-up balloon

Small plate

Salt and pepper


The world revolves around the atom, the smallest unit of measurement that we have, and within it, the eentsy weentsy electron. Did you know that everything is always moving? Not just that things are hyper, like when you can't pay attention in class. It's that everything is composed of atoms, and atoms have electrons, which are always moving. Nature is based on electricity, you see.


But everything isn't jolting around all the time because of electromagnetic force. That's what controls the space within atoms, acting as a sort of "glue" to keep electrons and protons in place. EXCEPT . . . electromagnetic force does carry an electrical charge. A "charge" is a property within all of our elementary particles of matter that gives rise to all kinds of motions and interactions.


Within an atom, there will be a proton with a positive charge (you can remember that because of the "pro" in "proton" - and an electron with a negative charge. They're opposites, and they attract. So if you put a positive proton next to a negative electron, they're going to stick together. Meanwhile, if you put a negative electron next to another negative electron, they're going to want to stay apart. That's called "repulsion." It's the same thing you do when you see something gross, that makes you sick, like your little brother's messy room - just kidding.


Anyway, electromagnetic force is stronger than gravity and has a ton to do with what goes on in your everyday life. Since atoms stick together and form molecules by sharing electrons with each other, we experience massive amounts of electromagnetic force in every molecule of our being, and our world, every moment of every day. Ironically, we aren't even usually aware of it.


But we can do these fun experiments to see electron transfer up close and personal. They're fun, so we'll get a . . . CHARGE out of it!



Shooting Puffed Rice
Charge a plastic spoon by rubbing a piece of woolen cloth over it several times.  Hold it over a dish containing puffed rice cereal.  The cereal puffs jump up and remain hanging on the spoon, until suddenly they shoot wildly in all directions.
What happens? The puffed rice grains are attracted to the negatively-charged spoon and cling for a time. Some of the electrons pass from the spoon and have the same charge. Because like charges repel one another, the puffed rice grains fly away from the spoon.
Coiled Snake

Cut a spiral -shaped coil from a thin piece of tissue paper, about 4 inches square. Lay it on a tin lid. Bend the center of the coil -- its "head" -- upward. Rub a fountain pen vigorously with wool cloth. Hold the pen over the coil.  It rises, like a living snake, and reaches upwards. See what happens when the paper touches the pen.
What happens? In this case, the pen has taken electrons from the woolen cloth and attracts the uncharged paper. On contact, the paper falls, because it takes part of the negative electric charge in the pen and gives it up immediately to the metal lid, which is a good conductor. Since the paper is now uncharged again, it is again attracted upwards until the fountain pen has lost its charge.

Magic Wand


Rub the woolen cloth briskly back and forth along both sides of the comb. Tear another piece of tissue paper into little pieces. The comb will "pick them up." You can re-charge the comb and "pick up" ping-pong balls or a blown-up balloon. Now tell your friends that you can make an inside-out salt and pepper shaker. sprinkle salt and pepper on a plate so that they are not clumping up, re-charge your comb very well, and then hold it one inch above the plate. The pepper will leap onto the comb - but the salt won't move.


What happens: The comb has been made negatively-charged by rubbing it with the wool, so when it approaches the paper, ping-pong balls or balloon, the electrons within these "neutral" objects retreat away from the negatively-charged comb. So the edges of these objects shift over from "neutral" to positive charges, making them attracted by the negatively-charged paper. Why did the pepper "jump" but not the salt? Because the pepper is lighter in weight than the salt, and could overcome the force of gravity more easily. Note: if you touch your negatively-charged comb to these objects, or rub them to get them to be negatively charged, too, you will see that they will suddenly repel the comb, because the interaction is no longer "opposites attract."


By Susan Darst Williams Experiments 03 2008

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