The Triboelectric Series: An Introduction for Static Electricity Labs
Product Management Coordinator for Physical Science
Static electricity is a part of every physical science and physics class. Somewhere in those classrooms or equipment closets is a set of equipment for static electricity experiments. The set might include an electroscope, even a Van de Graaff generator, and there's probably a box of mystery materials—several different cloths and some rods usually made of rubber, glass, acrylic, and perhaps a few others. You may be familiar with experiments that involve rubbing the cloths on the rods to generate a static charge, but which cloths go with which rods? Does it matter? Static electricity experiments can be unreliable because conditions such as dust in the air or humidity can have a significant effect, making it hard to know if the cloths and rods are being used in the right combination.
There is a way to know which materials work best together to generate static charge through friction. The triboelectric series is a list of materials that indicates by position on the list which materials are capable of acquiring a positive or negative charge and the relative strength of those charges. It is sort of like an answer key for static electricity labs.
The study of electricity dates back to ancient Greece. Around the 6th century BCE, the Greeks discovered that if you rub amber (fossilized tree resin) with a cloth, for example wool, the amber would pick up lightweight objects such as straw or feathers. The prefix tribo means “to rub,” and the word “electricity” comes from the Greek word for amber, elektron. The triboelectric effect refers to rubbing an object to give it an electrical property, like amber when it is rubbed with wool.
Sixth-century BCE technology had not progressed enough to develop the study of electricity much further, and it was 2,000 years later before any more significant progress in the field of static electricity. During the 17th and 18th centuries, scientists including William Gilbert, Alessandro Volta, and Benjamin Franklin conducted experiments with static electricity, using experimental devices such as the electroscope, the electrophorus, and the Leyden jar. Their experiments fostered an understanding of electric charge, which eventually led to the development of modern technologies that use current electricity, such as generators, telephones, radios, and computers.
The triboelectric series
The first published triboelectric series is credited to John Carl Wilcke from a paper published in 1757. The following list is a triboelectric series based on materials often found in classroom static electricity kits.
+ More Positive +
- More Negative -
Materials at the top of the list become positively charged and materials at the bottom become negatively charged. Objects that are farther apart on the list create a stronger charge when rubbed together. “Rubber Balloon” and “Hair” are far apart on the list, as are “Wool” and “Styrene.” Rubbing these objects together provides a good charge.
This list should give you a good starting point to begin experimenting with the materials in your static electricity kit.