Explanation of the Causes of Static Electricity - Succeed in Physical Science. Also refer to physics, charges, electron, proton, force, adhesion, atom, Bohr, solar system model, chemical bonding, Periodic Table, Triboelectric Series, friction, Ron Kurtus, School for Champions. Copyright © Restrictions
Causes of Static Electricity
by Ron Kurtus (revised 7 May 2008)
Static electricity occurs when there is an excess of positive (+) or negative (−) charges on an object's surface. This condition is caused from rubbing certain materials together. Static electricity is not caused by friction, as is popularly thought. Instead, it is caused by the triboelectric effect. The position of the material in the Triboelectric Series determines how effectively the charges will be exchanged.
Questions you may have include:
- How do you cause excess charges?
- What about friction?
- What is the Triboelectric Series?
This lesson will answer those questions. There is a mini-quiz near the end of the lesson.
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(Note: If you are looking for information on preventing shocks, see Controlling Static Electricity.)
Causing excess charges
Putting certain materials together and then pulling them apart causes excess electrical charges to be created on their surfaces. This can be done by pushing them together and pulling them apart or by rubbing the materials together, which is the main way static electricity is created.
Excess of charges
Most matter is electrically neutral. That means its atoms and molecules have the same number of electrons as protons. If a material somehow obtains extra electrons and attaches them to the atom's outer orbits or shells, that material has a negative (−) charge. Likewise, if a material loses electrons, it has an excess of positive (+) charges. The electric field from the excess of charges then causes the static electric effects of attraction, repulsion or a spark.
Stealing electrons
According to Solar System Model (or Bohr Model) of the atom, electrons are in orbits or shells around the nucleus. A maximum number of electrons are allowed in each orbit. Forces in each atom seek to reach that maximum number, such that if an element is just one electron short of the maximum amount in its outer orbit, it would try to "steal" an electron from another element that may be just starting its outer orbit. This is the basis of chemical reactions.
Adhesive force takes electrons
That force will also tend to hold two different materials together. In that situation, the force is called the adhesive molecular force. When different materials are pressed together and then pulled apart, the adhesive molecular force pulls electrons from material unto the other. This creates the static electricity.
You can see this effect with a piece of Scotch tape or similar tape. First verify that it is not attracted to your finger. Then stick it to some surface and then pull it off. Put you finger near the tape and it will now be attracted to your finger, showing that there is an excess of charges on the tape.
Not caused by friction
Although your can create static electricity by pressing materials together and pulling them apart, rubbing them together works even better, except in the case of something sticky like tape.
One unfortunate result from saying that rubbing materials creates static electricity is that most people think that friction causes the charges to build up. It is not friction that causes static electricity, rather it is the adhesive forces that pull off electrons.
Triboelectric Series
The Triboelectric Series lists materials according to how likely they are to let go of electrons or to take on electrons from other materials. Most of the materials in the Triboelectric Series are complex compounds and the release or attraction of electrons has to do with their molecular structure or geometry.
Dry human skin and rabbit fur have the greatest tendency to give up electrons when rubbed on something and become positively (+) charged. Teflon and vinyl have the greatest tendency to become negatively charged (−) when rubbed. If you want to create static electricity, rubbing fur on Teflon should give the best results.
(See Materials Causing Static Electricity for more information.)
Summary
Static electricity occurs when there are an excess of positive (+) or negative (−) charges on an object's surface. You can create static electricity by rubbing certain materials together. Static electricity is not caused by friction. The position of the material in the Triboelectric Series determines how effectively the charges will be exchanged.
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Resources
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Mini-quiz to check your understanding
1. What happens to an atom that loses some electrons?
2. How does friction cause electrons to go from one material to another?
3. If you pressed your hand on some Teflon and then pulled it away, what would happen?
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.
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Causes of Static Electricity