physics//electromagnetism//electric charge

Electric charge is the property of matter that makes particles attract or repel each other electrically, and it is the quantity every circuit moves around: a battery stores it, a wire carries it, a capacitor holds it. Electrons carry a negative charge, protons an equal positive one, and ordinary matter is neutral because the two balance; something becomes charged when electrons are added to it or taken away.

Electric charge is the property of matter that makes particles attract or repel each other electrically, and it is the quantity every circuit moves around: a battery stores it, a wire carries it, a capacitor holds it. Electrons carry a negative charge, protons an equal positive one, and ordinary matter is neutral because the two balance; something becomes charged when electrons are added to it or taken away.

Charge is measured in coulombs. One coulomb is a lot of electrons, about 6.2×10186.2 \times 10^{18}6.2×1018 of them, and it is also exactly what a current of one ampere delivers in one second. Charge is conserved: it is never created or destroyed, only moved, so every charge that leaves one place turns up in another.

Like charges repel and opposite charges attract, and the force falls with the square of the distance. Rather than acting at a distance, each charge sets up an electric field around it, and other charges feel that field.

Free charge is what conducts. In a metal the outer electrons are loose and drift through the crystal; in an electrical insulator they are bound to their atoms. In a solution, as in the body, the free charges are ions (sodium, potassium, chloride, calcium), which is why the nervous system runs on ions rather than electrons.

Charge piled on an object with nowhere to go is static electricity; charge moving along a path is an electric current, how much of it passes a point per second.