# How Does Static Electricity Work?

Have you ever gotten a shock from touching a doorknob, or seen your hair get frizzy on particularly cold, dry days? If you’ve had any of these experiences, you've encountered static electricity. Static electricity is the buildup of electric charge (positive or negative) in one location. It's also called “electricity at rest.”

### Key Takeaways: Static Electricity

• Static electricity occurs when charge builds up in one place.
• Objects typically have an overall charge of zero, so accumulating a charge requires the transfer of electrons from one object to another.
• There are several ways to transfer electrons and thus build up a charge: friction (the triboelectric effect), conduction, and induction.

## The Causes of Static Electricity

An electrical chargedefined as either positive or negative—is a property of matter that causes two electrical charges to attract or repel. When two electrical charges are of the same kind (both positive or both negative), they will repel one another. When they are different (one positive and one negative), they will attract.

Static electricity occurs when charge builds up in one place. Typically, objects are neither positively or negatively charged—they experience an overall charge of zero. Accumulating a charge requires the transfer of electrons from one object to another.

Removing negatively charged electrons from a surface will cause that surface to become positively charged, while adding electrons to a surface will cause that surface to become negatively charged. Thus, if electrons are transferred from Object A to Object B, Object A will become positively charged and Object B will become negatively charged.

## Charging by Friction (Triboelectric Effect)

The triboelectric effect refers to the transfer of charge (electrons) from one object to another when they are rubbed together, via friction. For example, the triboelectric effect may occur when you shuffle across a carpet wearing socks during the winter.

The triboelectric effect tends to occur when both objects are electrically insulating, meaning electrons cannot freely flow. When the two objects are rubbed together and then separated, the surface of one object has gained a positive charge, while the surface of the other object has gained a negative charge. The charge of the two objects after separation can be predicted from the triboelectric series, which lists materials in the order in which they are prone to become positively or negatively charged.

Because electrons cannot freely move, the two surfaces can remain charged for a long time, unless they are exposed to an electrically conducting material. If an electrically conducting material like metal is touched to the charged surfaces, the electrons will be able to move freely, and the charge from the surface will be removed.

This is why adding water to hair that is frizzing due to static electricity will remove the static. Water containing dissolved ions—as is the case with tap water or rainwater—is electrically conducting and will remove the charges that have accumulated on hair.

## Charging by Conduction and Induction

Conduction refers to the transfer of electrons when objects are placed in contact with one another. For example, a surface that is positively charged can gain electrons when it touches a neutrally charged object, causing the second object to become positively charged and the first object to become less positively charged than it previously was.

Induction does not involve a transfer of electrons, nor does it involve direct contact. Rather, it uses the principle that "like charges repel and opposite charges attract." Induction occurs with two electrical conductors, because they allow charges to move freely.

Here is an example of charging by induction. Imagine that two metal objects, A and B, are placed in contact with one another. A negatively charged object is placed to the left of Object A, which repels the electrons on the left side of Object A and causes them to move to Object B. The two objects are then separated, and the charge redistributes itself over the entire object, leaving Object A positively charged and Object B negatively charged overall.

## Sources

• Beaver, John B., and Don Powers. Electricity and Magnetism: Static Electricity, Current Electricity, and Magnets. Mark Twain Media, 2010.
• Christopoulos, Christos. Principles and Techniques of Electromagnetic Compatibility. CRC Press, 2007.
• Vasilescu, Gabriel. Electronic Noise and Interfering Signals Principles and Applications. Springer, 2005.
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