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Monday, December 17, 2012

Static Electricity

This is an incredibly simple and fun activity.

Roll of clingfilm or plastic wrap. In the United States, Reynolds brand tends to work the best.
Roll of paper towels
Small bits of paper (Empty the hole punch ;=] )
Equally small pieces of aluminum foil, rubber bands, salt, pencil shavings, plastic.

Part 1
Distribute a square or rectangle of plastic wrap and paper towel to each student.
Have students flatten the plastic wrap on their desktop.
Next, students rub the plastic wrap with the paper towel.
As they rub, ask them what they think the plastic wrap will do if they lift it by opposite corners. Invariably, they will say it will wad into a ball or similar answers.
After a minute or two, have students place the paper towel aside.

Instruct students to lift by opposite corners. Surprisingly, the wrap will open instead of collapsing. This is because they created a charge on the opposite side, thus creating the same and opposite charge on the bottom. Like charges repel.
They will want to do this again which I always allowed them to do so.

Part II
I pass out the items to test in a particular order with the salt being last. When they recharge their wrap and salt adheres to the wrap, the wrap tears.

Have students charge the wrap and hold it over the small pieces of paper. They will be attracted to the wrap.
Have students charge the wrap and hold it over various sizes of aluminum foil.
Have students charge the wrap and hold it over small bits of rubber and plastic.
Have students charge the wrap and hold over salt. Students enjoyed this the most. Salt is an ionic compound and is very attracted. I liked students to observe that as the charge lessened, the salt began to drop. Recharging the wrap and testing again is good.
Have students recharge the wrap and hold over pencil shavings.

You can choose more items to test. The more ionic a substance is, the greater the reaction. Covalent solids like rubber are not affected by the charge.

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