SfC Home > Physical Science >

Explanation of the basics of Static Electricity - Succeed in Physical Science. Also refer to physics, electricity, static cling, attract, repel, atoms, electrons, negative, protons, positive, lightning, Ben Franklin, Ron Kurtus, School for Champions. Copyright © Restrictions

Basics of Static Electricity

by Ron Kurtus (revised 28 August 2004)

Static electricity is the situation where electrical charges build up on the surface of a material. It is called “static” because there is no current flowing as in AC or DC electricity. Static electricity is usually caused when materials are rubbed together. The result is that objects may be attracted to each other or may even cause a spark to jump from one object to the other. Common examples of static electricity in action are static cling, flyaway hair and the sparks that can occur when you touch something.

Questions you may have include:

• What causes static electricity?
• Why do things attract or repel?
• What causes a spark?

This lesson will answer those questions. There is a mini-quiz near the end of the lesson.

Useful tools: Metric-English Conversion | Scientific Calculator.

(Note: If you are looking for information on how to stop getting static electricity shocks, see Controlling Static Electricity.)

Cause of static electricity

Static electricity is usually caused when certain materials are rubbed against each other, like wool on plastic or the soles of your shoes on the carpet. The process causes electrons to be pulled from the surface of one material and relocated on the surface of the other material.

Rubbing a balloon on a wool sweater
creates charges on the surfaces

The material that loses electrons ends up with an excess of positive (+) charges. The material that gains electrons ends up an excess of negative (-) charges on its surface.

Electrons pulled from orbit

The gain or loss of electrons can be explained by recalling that atoms consist of a nucleus of neutrons and positively charged protons, surrounded by negatively charged electrons. Normally, there is the same number of electrons as protons in each atom.

But if some object pulls away electrons from their orbit or shell around the nucleus, that causes the atom to have a positive charge because it has more protons than electrons. Likewise, the other material will have extra electrons in its shell, giving the atoms a negative charge.

Charges on surface

Note that the charged atoms are on the surface of the material. Static electricity is different than regular electricity that flows through metal wires. Most of the time the materials involved in static electricity are nonconductors of electricity.

If electrical charges build up on the outside of a metal, most of them will dissipate into the metal, similar to an electrical current.

Prefers dry air

When the air is humid, water molecules can collect on the surface of various materials. This can prevent the buildup of electrical charges. The reason has to do with the shape of the water molecule and its own electrical forces.

Thus, static electricity is formed much better when the air is dry or the humidity is low.

Force field causes attraction

An object that has static electricity charges built up on its surface has an electrical force field coming from the surface. This field will mildly attract neutral objects or those with no charge. The field will strongly attract an object that has an opposite charge on its surface. From this we get the expression: "Opposites attract."

If two objects have the same charge, the electrical force field will cause those objects to push away from each other or repel.

Attraction

Rub a balloon on a wool sweater. The balloon collects negative electrical charges on its surface and the wool collects positive charges. You can then stick the balloon to the wall, which does not have an excess of either charge. The balloon will also stick to the wool, although the charges may jump back to the original material in a short time.

You can also run a comb through your hair to charge the comb with static electricity. The comb can then be used to attract neutral pieces of tissue.

Picking up tissue with a comb

Repulsion

Comb your hair on a dry day or after using a hair drier. The plastic comb collects negative charges from the hair, causing the hair to have an excess of positive charges. Since like charges repel, the hair strand will tend to push away from each other, causing the "flyaway hair" effect.

Why sparks fly

When two objects that have opposite charges get near each other, the electrical field pulls them together.

What actually happens is that the negatively charged (-) electrons are attracted to the atoms in the other material that have an excess positive (+) charge. Things are much more stable if all the atoms have an equal number of (+) and (-) charges.

Strong forces hold electrons

The reason the electrons can't leave their present material is because of strong molecular forces that keep them where they are. If there are enough positive (+) charges attracting them, and the distance is not too great, some of the electrons will break loose and fly across the gap to the (+) side.

Once it starts

Once a few electrons start to move across the gap, they heat up the air, such that more and more will jump across the gap. This heats the air even more. It all happens very fast, and the air gets so hot that it glows for a short time. That is a spark.

The same thing happens with lightning, except on a much larger scale, with higher voltages and current.

Ben Franklin

Ben Franklin proved that lightning was static electricity by flying a kite in a storm and detecting static electricity by seeing the hairs on the kite string stand on end and creating a spark with a metal key. This dangerous experiment showed that static electricity was being formed in the clouds by the rain.

(See the biography of Ben Franklin's life.)

Summary

Rubbing certain materials together can cause the buildup of electrical charges on the surfaces. Opposite charges attract and same charges repel. Either charge will be attracted to something of neutral charge. Sparks are an extreme case of electrons being attracted to an object that has a positive charge.

Reader Questions and Comments

Electrify others by doing your best

Resources

The following resources provide information on this subject:

Websites

Physical Science Resources

Books

Top-rated books on Static Electricity

Miscellaneous

Mini-quiz to check your understanding

1. What happens to an atom if something pulls an electron from it?

2. Which of the following will usually create static electricity?

3. What can cause electrons to jump across a gap and cause a spark?

If you got all three correct, you are on your way to becoming a Champion in Physical Science. If you had problems, you had better look over the material again.

What do you think?

Do you have any questions, comments, or opinions on this subject? If so, send an email with your feedback. We will try to get back to you as soon as possible.

Share link

Feel free to establish a link from your website to pages in this site.

Or use our form to send this link to yourself or a friend.

Students and researchers

The Web address of this page is
www.school-for-champions.com/science/static.htm.

Please include it as a reference in your report, document, or thesis.

Where can you go from here?

School for Champions

Physical Science topics

Basics of Static Electricity