The shock caused by static electricity reveals how you can have more power at your fingertips than you ever imagined.
Static electricity builds when electrons leap between two objects that have opposing electrical charges. A stunning handshake occurs when one person has a negative charge, and the other doesn't.
All materials are made up of molecules, and all molecules have tiny atoms, with positively charged protons, neutral neutrons, and negatively charged electrons floating around. Most of the time an atom is neutral with the same number of protons and electrons.
When an atom's proton and electron numbers are uneven, the electron dance begins.
If you place two different materials next to each other, electrons will start jumping from one material to the other. Conductive materials like metals and carbon hold onto their electrons tightly. Whereas insulating materials, such as plastic, can be charged by friction because they easily gain or lose electrons.
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What's going on
In 600 B.C., the Greek philosopher Thales observed that some combinations of materials have more potential to make sparks fly than others.
Materials can be catalogued in order of their tendency to become charged, from positive to negative. The lower an item sits on the list, the more likely it will attract more electrons and become negatively charged. Rubbing objects far from each other on the list creates a bigger charge than objects closer together.
For example, polishing a glass plate with a silk scarf electrifies the scarf so that it acts like a magnet. At even more disparate ends of a series, the friction of rabbit's fur on a Teflon pan generates additional electricity.
When you stride across a wool carpet in leather shoes, your shoes pick up extra electrons from the carpet with each step.
By the time you lift your foot up off the ground, the electrons will have spread around your entire body, giving you a negative charge. The next time you put your foot on the carpet, your shoe doesn't have any extra electrons, but your head might. So more electrons make the leap to your foot.
"As you keep walking across the floor, you become full of electrons," said Todd Hubing, from the Electromagnetic Compatibility Laboratory at the University of Missouri-Rolla. "Eventually more electrons don't want to come up on you because you're so charged up. You end up with a high voltage, about 20,000 to 25,000 volts."
That's serious power at your fingertips, considering a normal electrical outlet on the wall is only around 100 volts of electricity.
Here and gone
Electrons are like fickle friends. Even though they were attracted to you in the first place, they don't like to hang around for long and they're always looking for a way out.
When you reach for a positively charged doorknob, electrons flee and you get zapped.
"The voltage is high enough that when you're about an inch apart, it causes the air to break down and it creates a spark," Hubing explained.
From the impact of your voltage, the air between your hand and the knob grows extremely hot and instantly turns to plasma, a fourth state of matter that differs from solids, liquids, or gases.
The plasma gives off a bright flash. The electrifying light show works just like a lightning bolt. Similar to thunder, the pop sound is the result of air rapidly expanding and collapsing.
Static electricity causes problems for electronics manufacturers, because a strong charge can damage electronic components such as video game cartridges.
Humidifying the air helps cut down static electricity.
Electrons build up more easily in dry places. On humid days, shocks are less common because a thin layer of water molecules coats most surfaces, which allows electrons to flow more freely and makes almost everything conductive and static-free.
A spritz of water can help untangle skirts and calm repulsive hair. Dryer sheets work similarly, coating tumbling clothes with a conductive substance.
Some manufacturing workers are required to abide by strict clothing regulations, avoiding sweaters and hats that might encourage static. Technicians might wear wrist straps that are attached to the floor with a metal wire, sending extra electrons out of the room and into the ground.
Manufacturing plants can also use air ionizers to settle electron behavior.
The machines fill the air in a room with some molecules that are missing electrons, and some that have too many electrons, called ions. As they float around the room searching for balance, the electrons match up with their opposites.
"They can neutralize the charge on a person," Hubing explained. "The ionizers prevent static electricity buildup. But they're only moderately effective."