Published: 22 January, 2004

Dry air makes static electricity more noticeable in winter

Where does static electricity come from? How does it get in my cat's fur? Why is it worse in winter? How do dryer sheets get static out of clothes?

Everything around us contains tiny electrically charged particles (too tiny to see!) called "electrons" and "protons." Electrons are negatively charged, while protons are positively charged. Protons and most electrons are held in place inside objects, but some electrons can move around more easily. Negative and positive charges (electrons and protons) attract each other, especially when they're close together, while negative charges alone (electrons) repel each other. So objects normally like to have the same numbers of electrons and protons--they're electrically "neutral" or "uncharged." But some objects are more "greedy" for electrons than other objects.

When two different objects touch each other or are rubbed together (like a comb and your hair or a brush and your cat's hair or different kinds of clothing in a clothes dryer), electrons can be "stolen" by the "electron-greedy" object from the other object. One object now has too many electrons (the comb or brush) and is negatively charged, while the other has too few electrons and is positively charged (the hair). The "crackles" you often hear when rubbing objects together are sparks made by rubbed-off electrons jumping back onto the object they came from to try to make both objects neutral again. But lots of the rubbed off electrons can't make it back, so the objects stay electrically charged...at least for awhile. This is static electricity.

In the winter, air is dry--there's very little water vapor in it. In the summer, air is more humid--it contains more water vapor. Water is an "electrical conductor"--it makes it easier for electrons to move from one place to another. Water in the air lets extra electrons on charged objects leak off into the air and find their way back to charged objects that have too few electrons. Humid air helps to "discharge" static electricity this way, so we don't notice it as much in the summer. In the winter, dry air makes it harder for electrons to leak off, so static electricity discharges by crackling sparks.

When dryer sheets tumble around with clothes inside a clothes dryer, the heat and tumbling move chemicals from the dryer sheets onto the clothes, coating or "lubricating" the clothes with a thin layer of these chemicals. Now the surfaces of the clothes rubbing together are all equally greedy for electrons since they're all coated with the same chemicals from the dryer sheets. When two different pieces of these clothes touch and rub against each other, neither one is able to steal very many electrons from the other, so the clothes stay uncharged or neutral. But now there is a layer of chemicals on the clothes (and on the inside of the dryer) that can build up from drying to drying if the washing machine doesn't wash them all off. Before using dryer sheets you should always check the labels on your clothing (especially clothing that is supposed to be flame resistant) and the directions on the box of dryer sheets and in your dryer's instruction manual to see if they're okay to use. But if you are able to use them, dryer sheets can make clothes feel soft and smell nice, and they do help prevent static electricity!