Have you ever received a shock after touching a light switch or rubbed a balloon on your hair and then stuck it to your head? If you have, then you have experienced the power of static electricity. Static electricity, also known as the triboelectric effect, is a buildup of electric charge between two objects that come into contact with each other. Rubbing objects together is a common way to produce static electricity because it repeatedly brings the objects in contact with each other.
To understand static electricity, we have to start with some basic properties of matter. All matter is made up of atoms. Each atom consists of positively charged protons, negatively charged electrons, and neutrons that have no charge. The movement of electrons through a material produces electricity. Materials that allow electrons to move freely through them are called conductors. Gold, copper, and silver are good conductors. Materials that don’t allow the free movement of electrons are called insulators. Plastics and rubber are two examples of insulators.
Static electricity occurs between insulators—materials that do not conduct electricity. This phenomenon is called static electricity because electrons do not move through the materials, but rather transfer between them. Most of the time, electric charge in a material is balanced so an object has no charge. However, bringing objects in contact with each other—for example, when you rub two objects together—can lead to a transfer of electrons. One object loses electrons and becomes positively charged, while the other object gains electrons and becomes negatively charged. The chemistry of an atom determines whether it gains or loses electrons. When your feet rub against carpet, your body collects electrons from the carpet. The electrons cling to you until they can be released. Touching something that conducts electricity, like a metal doorknob, discharges the electrons into the doorknob and gives you a jolt.
Scientists have used the electron-transfer explanation of static electricity for hundreds of years, but it turns out static electricity is a bit more complex than that. It is not only electrons that transfer between materials, but also both positive and negatively charged ions. Ions are atoms of an element that have already lost or gained an electron and exist in a charged state. In some cases, individual atoms or molecules at the surface of each material may be exchanged as well. For example, when scientists rubbed Teflon and silicone together, fluorine atoms from the Teflon transferred to the silicone and silicon atoms from the silicone transferred to the Teflon. At the end of the exchange, each material will end up with an overall positive or negative charge. Researchers don’t currently understand how or why this transfer occurs, but investigations are ongoing.
So how do we explain why static electricity causes a balloon to stick to hair? This also has to do with electric charge. Opposite charges attract, while like charges repel each other. When you rub a balloon on your head, the balloon gains an overall negative charge due to electron and ion transfer from your hair. This loss of negative charges gives your hair an overall positive charge. Your hair sticks to the balloon because opposites attract. The more you rub the balloon against your hair, the more negatively charged it will become and the stronger it will stick to your hair.
Not all objects can gain or lose negative charges freely. Some materials hold tightly to electrons, while others give up their electrons with ease. It all depends on the internal structure of the atoms that make up the material. A triboelectric series, as illustrated above, lists materials in terms of their ability to become more positively or more negatively charged. Objects that are farther apart from each other will create a stronger charge imbalance when rubbed against each other. Hair and balloons are far apart, which is why rubbing a balloon against hair produces static electricity. Rubbing objects that are closer together on the series, like silk and wool, will not generate as much static charge as objects that are further apart.
While the shock we get from static electricity can seem like a nuisance, the phenomenon has practical applications. Photocopiers and laser printers use static electricity to transfer ink to paper. Scientists are also working on ways to harness these tiny jolts of energy. Researchers at the Georgia Institute of Technology created a triboelectric generator that captures the electricity produced by static. While these generators work on a small scale, they could one day be powerful enough to keep in your pocket to charge a phone.
To learn more about static electricity, check out this article from American Scientist.
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