We’ve all have experienced static electricity in one way or another. Those unexpected little shocks we get when we touch a doorknob or some other metallic object, the balloons that stick to the wall after being rubbed in the head, or hair itself standing straight when it comes close, all are produced by static electricity. Most of the time it is produced when two objects come in contact or are rubbed together.
What is Static Electricity?
All materials are made up of molecules, and all molecules have tiny atoms, with positively charged protons, neutral neutrons, and negatively charged electrons. 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.
Static electricity is generated when any material gains or loses electrons and becomes positively (when it loses electrons) or negatively charged (when it gains electrons). The accumulated charges are what’s called static electricity. 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.
In 600 BC, 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.
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.
Practical Uses of Static Charges
Dust removal: There are some appliances that can eliminate dust from the air, like air purifiers. They use static electricity to alter the charges in the dust particles so that they stick to a filter of the purifier that has an opposite charge as that of the dust (opposite charges attract each other). This effect is also used in industrial smokestacks to reduce the pollution that they generate. The effect is basically the same as the home air purifier..
Photocopy: Copy machines use static electricity to make ink get attracted to the areas where we need the information copied. It uses the charges to apply the ink only in the areas where the paper to be copied is darker (usually this means text or other information) and not where the paper is white, this process is called xerography.
Car painting: To make sure a car’s paint is uniform and that it will resist the high speeds and weather to protect the car’s metal interior, it is applied with a static charge. The metal body of the car is submerged in a substance that charges it positively, and the paint is charged negatively.
This process ensures a uniform layer of paint, since when there is enough negative paint in the car the extra will be repelled by the paint already in the car. It also ensures that the paint won’t fall off.