Electrical force is responsible for holding together the atoms and molecules from which matter is composed. In this way, electricity determines the structure of every object that exists. Electricity is also associated with many biological processes.

In the human body, electrical signals travel along nerves, carrying information to and from the brain. Electrical signals tell the brain what the eyes see, what the ears hear, and what the fingers feel. Electrical signals from the brain tell muscles to move. Electrical signals even tell the heart when to beat.

One of the most important properties of electricity is electric energy.

During the 1800's, people learned to harness electricity to do work. Inventors and scientists learned how to generate electric energy in large quantities. Inventors and scientist found ways to use that energy to produce light, heat, and motion. They developed electric devices that enabled people to communicate across great distances and to process information quickly. The demand for electric energy grew steadily during the 1900's.

Several thousand years ago, the ancient Greeks observed that a substance called amber attracted bits of lightweight material, such as feathers or straw, after it was rubbed with cloth. Amber is fossilized pitch from pine trees that lived millions of years ago

Amber is a good electric insulator, so it easily holds electric charge. Greeks were experimenting with static electricity when they rubbed amber. The Greek word for amber is electron. The English words electricity and electron come from this word. Greeks, Chinese, and other people, knew of another substance that could attract things. It was a black rock called lodestone or magnetite. Lodestone attracts iron objects, which tend to be heavy. On the contrary, amber attracts only light things, like straw.

In 1551, Italian mathematician Girolamo Cardano, also known as Jerome Cardan, realized that the attracting effects of amber and of magnetite must be different. Cardano was the first to note the difference between electricity and magnetism. In 1600, William Gilbert reported that such materials as glass, sulfur, and wax behaved like amber. When rubbed with cloth, they too attracted light objects. Gilbert called these materials electrics. He studied the behavior of electrics and concluded that their effects must be due to some kind of fluid.

In the 1730's, French scientist Charles Dufay found that charged pieces of glass attracted amber like substances but repelled other glass like substances. Dufay decided that there must be two kinds of electricity's. He called them vitreous (for glass like substances) and resinous (for amber like substances). Dufay had found negative and positive electric charge, though he thought of them as two kinds of "electric fluid."

Benjamin Franklin, an American scientist and statesman, began to experiment with electricity in 1746. Franklin thought that there was only one kind of electric fluid. He theorized that objects with too much fluid would repel each other, but they would attract objects with too little fluid. If an object with an excess of fluid touched an object deficient in fluid, the fluid would be shared. Franklin's idea explained how opposite charges cancel each other out when they come in contact. Franklin used the term positive for what he thought was an excess of electric fluid. He used the term negative for a deficiency of fluid. Franklin didn't know that electricity is not a fluid.

Rather, electricity is associated with the charges of electrons and protons. In 1752, Franklin performed his famous experiment, flying a kit during a thunderstorm. When the kite and the string became electrically charged, Franklin concluded that the storm clouds were themselves charged. He became convinced that lightning was a huge electric spark. Luckily, lightning didn't strike his kite; if the kite were strike by a lightning he would probably have been killed.

In 1767, Joseph Priestley described the mathematical law that shows how attraction weakens as the distance between oppositely charged objects increases. In 1785, Charles Augustin de Coulomb confirmed Priestley's law. Coulomb showed that the law also held the true for the repulsive force between objects with the same charge. The principle is now known as Coulomb's Law.

In 1771, Luigi Galvani found that the leg of a recently killed frog would twitch when touched with two different metals at the same time.

In the late 1790's, Alessandro Volta showed that chemical action occurs in a moist material in contact with two different metals. The chemical action results in an electric current. The flow of current had made Galvani's frog twitch. Volta collected pairs of disks, consisting of one silver and one zinc disk. He separated the pairs with paper or cloth moistened with salt water. By piling up a stack of such disks, Volta constructed the first battery, called a voltaic pile.

German physicist Georg S. Ohm devised a mathematical law to describe the relationship between current, voltage, and resistance for certain materials. According to the Ohm's law a larger voltage can push a larger current through a given resistance. Also, a given voltage can push a larger current through a smaller resistance.

In 1820, Hans C. Oersted found that an electric current flowing near a compass needle will cause the needle to move. Oersted was the first to show a definite connection between electricity and magnetism.

During the 1820's, Andre Marie Ampere discovered the mathematical relationship between currents and magnetic fields. That relationship is now known as Ampere's law. It is one of the basic laws of electromagnetism.

In the early 1830's, Michael Faraday and Joseph Henry independently discovered that moving a magnet near a coil of wire produced an electric current in the wire. Other experiments showed that electrical effects occur any time a magnetic field changes. Audio and videotape recording, computer disks, and electric generators are based on this principle. James Clerk Maxwell combined all the known laws covering electricity and magnetism into a single set of four equations. Maxwell's equations describe completely how electric and magnetic fields arise and interact. Maxwell made a new prediction that a changing electric field would produce a magnetic field. That prediction led him to propose the existence of electromagnetic waves, which we now know include light, radio waves, and X rays.

In the later 1880's, Heinrich R. Hertz showed how to generate the detect radio waves, proving Maxwell correct.

In 1901, Guglielmo Marconi transmitted electromagnetic waves across the Atlantic Ocean, setting the stage for radio, TV, satellite communications, and cellular telephones. G. Johnstone Stoney believed that electric current was actually the movement of extremely small, electrically charged particles. In 1891, Stoney suggested that these particles be called electrons.

In 1897, Joseph John Thomson proved the existence of electrons and showed that all atoms contain them. A research by Robert A. Milikan accurately measured the electron's charge.

Later,  scientist found out that electrons can be dislodged from a metal surface in a vacuum tube. A vacuum tube with most of the air removed. The tube contains electrodes with wires that extend through the glass. Linking batteries to the electrodes causes a current of electrons to flow within the tube. Adjusting the voltage can modify the current. Vacuum tubes can amplify, combine, and separate weak electric currents. This invention helped make radio, TV, and other technologies possible.

In 1947, John Bardeen, Walter H. Brattain, and William Shockley invented the transistor. Transistors do the same jobs as vacuum tubes, but they are smaller and more durable, and they use far less energy.

By the 1960's, transistors had replaced vacuum tubes in most electronic equipment. Ever since then, electronics companies have developed ever-smaller transistors. In present time, millions of interconnected transistors fit on a single chip called an integrated circuit. Many scientist hope that new electric devices will actually help curb the growing demand of electric energy.

Computers, for example, can control lights, air conditioning, and heating in buildings to reduce energy use. Compact fluorescent lamps, using miniature electronic circuits, provide the same light as ordinary light bulbs but use only one-fifth as much electric energy. Computer and modern communication systems enable people to work at home and save energy they would have used for transportation.