Electricity

Electrical charge is a fundamental property possessed by a few types of particles that make up atoms. Electrical charge is found with either positive or negative polarity. Positive charge exactly neutralizes an equal quantity of negative charge. Charges with the same sign repel while unlike charges attract. The unit of electrical charge is the coulomb, named for Charles Coulomb, an early authority on electrical theory.

The most obvious sources of electric charge are the negatively-charged electrons from the outer parts of atoms and the positively-charged protons found in atomic nuclei. Electrical neutrality is the most probable condition of matter because most objects contain nearly equal numbers of electrons and protons. Physical activities that upset this balance will leave an object with a net electrical charge, often with important consequences.

Excess static electric charges can accumulate as a result of mechanical friction, as when someone walks across a carpet. Friction transfers charge between shoe soles and carpet, resulting in the familiar electrical shock when the excess charge sparks to a nearby person.

Many semiconductor devices used in electronics are so sensitive to static electricity that they can be destroyed if touched by a technician carrying a small excess of electric charge. Computer technicians often wear a grounded wrist strap to drain away an electrical charge that might otherwise destroy sensitive circuits they touch.