Electric charge

Electric charge is a physical property of the subatomic particles of matter that allows objects to transmit electricity. Imbalances between oppositely charged particles called protons and electrons inside an object's atoms create electric charges. The imbalances allow the negatively charged electrons to move freely around the atom. Objects with atoms in which electrons are constantly moving have an electric charge and create electric fields. Electrically charged objects are known as conductors. Objects with no electric charge are called insulators. Some objects have both electrically charged atoms and uncharged atoms. The electricity created by the charged atoms quickly moves around to similar atoms and releases energy. This is known as static electricity. Meanwhile, conductors allow current electricity to flow. The two types of current electricity are direct current and alternating current.

Background

Eighteenth-century American inventor and diplomat Benjamin Franklin was not the first scientist to observe electricity, but he made important contributions to scientific knowledge of electrical currents. Franklin began studying electricity in the 1740s. At this time, many scientists believed electricity was created by the interaction of positive and negative electrical elements. Franklin believed electricity existed on its own and that only objects that had too much or too little electric "fluid" could interact with electricity. Franklin used the terms positive and negative to describe these objects.

In the 1750s, Franklin experimented with the conduction, or transfer, of electricity from one material to another by flying a kite with a metal key attached to it during a thunderstorm. According to varying accounts, lightning either directly struck the key, or the key simply picked up electric current in the atmosphere. In any case, this proved to Franklin that electricity transferred itself to electrically charged objects.

Scientists learned more about electricity over the next century and a half. Inventors such as Serbian-American Nikola Tesla and American Thomas Edison greatly advanced humanity's practical applications of electric currents. Edison invented the incandescent light bulb in 1879. He enthusiastically promoted the idea of direct current as the best use of current electricity. Edison rejected Tesla's suggestion that electricity could be practically applied using alternating current.

Edison believed his view to be correct, for direct current was simpler to produce, and no commercial markets yet existed for electric devices that used alternating current. In time, however, Tesla's developments in the field of alternating current led to the creation of the types of energy supplies that power much of the world in the modern era, such as electrical wall outlets.

Overview

A material's electric charge depends entirely on the makeup of its atoms. Atoms are the most basic units of matter. Atoms make up all living and nonliving objects in the universe. Atoms can be electrically charged based on the arrangement of their particles, known as protons, neutrons, and electrons.

At the center of every atom is a nucleus, where most of the atom's mass is located. Protons are the positively charged particles found in atomic nuclei. Neutrons are uncharged particles that are also found in the nuclei of most atoms. They are slightly heavier than protons. Electrons are the smallest subatomic particles—more than 1,800 times smaller than protons and neutrons. Electrons orbit atomic nuclei.

The number of electrons in an object's atoms usually determines whether that object has an electric charge. Atoms become electrically charged when the number of protons differs from the number of electrons. Atoms with the same amount of protons and electrons are not charged, since the particles cancel each other out. Atoms with more protons than electrons are positively charged. Atoms with more electrons than protons are negatively charged. Constant electron flow around an atom's nucleus generates an electric charge.

Objects capable of transferring electricity are called conductors, while objects that do not transfer electricity are called insulators. Metals conduct electricity because their atoms have freely moving electrons. Insulators prevent electricity from flowing through them because their electrons cannot move freely. Most materials with which people interact every day are insulators. This is why people do not get shocked from touching glass, plastics, and wood. Between insulators and conductors are semiconductors, which do not conduct electricity well but also are not full insulators. The metalloid silicon is a semiconductor. Superconductors, meanwhile, are materials that conduct electricity without any resistance. An example is the metal aluminum.

Two major types of electric charges exist: static electricity and current electricity. Static electricity is caused by a buildup of positively and negatively charged atoms in two objects separated by an insulator. A balloon rubbed against clothing loses some of its electrons to the clothing. This transfer releases static electricity, which makes the balloon cling to the clothing. Static electricity is also responsible for the minor shocks people may experience when dragging their feet across a carpet and then touching a metal doorknob.

Meanwhile, current electricity is caused by the constant movement of electrons from one atom of a substance to another. The two types of current electricity are direct current and alternating current. Batteries are an example of direct current, which flows in only one direction. Alternating current can continually reverse the direction of its flow. It is used to power appliances such as refrigerators, light bulbs, and microwaves.

People must take special precautions with materials that conduct electricity because electric shocks can severely injure or kill people. Ground wires, or earth wires, are a safety measure incorporated into many electric appliances. These wires connect to the ground to provide electricity with a location to flow if the appliance ever short-circuits and shocks itself. Without ground wires, people using the appliance at the time would get shocked. Ground wires safely divert stray electricity.

Factory workers could be in danger of electric shock if they do not follow safety measures. These may consist of working on insulator mats or wearing shoes with insulator soles. The rubber or other insulating material stops electricity from shocking workers. Other safety measures people can take when interacting with electric appliances include not using the appliances in wet conditions—because water conducts electricity—and always turning electric devices off before unplugging them to avoid being shocked.

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