You are actually fairly familiar with electric fields too, but you may not know it. Have you ever rubbed your feet against the floor and then shocked your brother or sister? Have you ever zipped down a plastic slide and noticed that your hair is sticking straight up when you get to the bottom? Both phenomena are caused by electric fields and they are everywhere!
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An electric field exists when at least one body is electrically charged. Atoms are filled with positively charged protons and negatively charged electrons. If an object has more electrons than protons, it will be negatively charged and if it has fewer electrons than protons, it will be positively charged. Electric fields, like magnetic fields, can attract and repel. If two bodies have the same kind of charge, that is either both are negative or both are positive, they will push themselves away from each other. If one body has a positive charge and the other has a negative charge, they will attract each other. Charged bodies can also attract bodies that are neither positive nor negative but are just neutral.
Electric fields are extremely common. If you comb your hair with a plastic comb, you cause that comb to have a small electric field. When you take off a fleece jacket or a polyester sweat shirt, you create an electric field that may be thousands of volts! Don’t worry, you can’t get hurt. There may be lots of voltage but there will be very little amperage. It’s the amperage that actually hurts you.
Here’s a simple experiment you can do that only needs four simple items:
– head of hair
– balloon
– yardstick or meterstick
– large spoon
Here’s what you do:
Download Student Worksheet & Exercises
Make sure you’ve tried out these Static Electricity experiments and learn how to light a bulb without plugging it into the wall!
Exercises
- What happens if you rub the balloon on other things, like a wool sweater?
- If you position other people with charged balloons around the table, can you keep the yardstick going?
- Can we see electrons?
- How do you get rid of extra electrons?
- Does the shape of the balloon matter?
- Does hair color matter?
- Rub a balloon on your head, and then lift it up about 6”. Why is the hair attracted to the balloon?
- Why does the hair continue to stand on end after the balloon is taken away?
- What other things does the balloon stick to besides the wall?
- Why do you think the yardstick moved?
- What other things are attracted or repelled the same way by the balloon? (Hint: try a ping pong ball.)
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I can think of a couple main reasons why the balloon might stop sticking to a window. Once you stick a balloon on a surface, some of the electrons may move from the balloon to that surface. This balances out the static charge and reduces the attraction. Try moving to a different window. Also, moisture in the air can prevent a build up of static. Try the experiment first thing in the morning, when it is often less humid, then again in the afternoon. I can think of two more things to try: 1) Try a different balloon. Do you notice a difference in how a new balloon sticks? 2) Ask a friend or family member the rub the balloon on their head. Will the same balloon stick again after doing that?
Hi Miss Aurora. I’m wondering why my balloon sticks to something at first, but it won’t stick to it again even if I rub it on my hair a lot. At first, my balloon stuck to the window for a really long time. After it fell, I rubbed it on my head again and it wouldn’t stick to the window or anything at all. Why?
Thanks. – Liam