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We’ve worked with static electricity before on Saturday Science. Even if you missed those installments, you might have played with static in the past. One fun thing to do is rub a balloon on your shirt until it’s got a nice static charge and then stick it to things: your hair, the wall, a cat, whatever. Static isn’t all just fun and games, though. In the right situation, it can be pretty useful. Say, for example, you spilled some salt and pepper and wanted to separate them instead of just throwing the whole thing out …
Materials:
- Salt
- Pepper
- 2 plates
- A plastic comb
- Some cloth
Process:
- Pour out some salt and pepper onto a plate and mix them all up. Oops!
- Rub your comb with your cloth for 15-20 seconds to build up a static charge. If it’s really dry that day, it may not take as long. If the air is humid, it may take a bit longer.
- Once your comb is all charged up, hold it about an inch above your salt and pepper pile. You’ll know it’s the right distance when the pepper starts to jump up and cling to the comb. Don’t go too close or you’ll start picking up salt, too!
- Every once in a while, brush the pepper off onto your second plate. You may have to charge up your comb again from time to time, but with some patience, you’ll be able to separate the pepper from the salt!
What's going on?
Normal electricity (or electrical current) is made of tiny particles called electrons, and static electricity is no different. Electrons are charged, and there are two kinds of charges that tiny particles can have: positive and negative. Electrons are negative. Negative and positive (or neutral, which means no charge) charges attract each other, they pull on each other. When you put your negatively-charged comb close to your neutral pepper, it starts to attract the tiny pieces of pepper. But why doesn’t the salt get attracted until the comb is closer? Well, the crystals of salt are heavier than the individual pepper grounds, so the charge has to be stronger to pick them up, which means the comb has to be closer. What else can you pick up with your new static comb?
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