Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic
interaction. Electrically charged matter is influenced by, and produces, electromagnetic fields. The interaction
between a moving charge and an electromagnetic field is the source of the electromagnetic force, which is one
of the four fundamental forces.
Electric charge is a characteristic of some subatomic particles. It is quantized in that, when expressed in
units of the so-called elementary charge e, it takes integer or fractional values. Electrons by convention have
a charge of −1, while protons have the opposite charge of +1. Quarks have a fractional charge of −1⁄3 or +2⁄3.
The antiparticle equivalents of these (positrons, antiprotons, and antiquarks, respectively) have the opposite
charge. There are other charged particles.
The discrete nature of electric charge was proposed by Michael Faraday in his electrolysis experiments, and
then directly demonstrated by Robert Millikan in his oil-drop experiment. In general, same-sign charged particles
repel one another, while different-sign charged particles attract. This is expressed quantitatively in Coulomb's
law, which states that the magnitude of the electrostatic repelling force between two particles is proportional
to the product of their charges and the inverse square of the distance between them.
The table below gives conversion factors to move back and forth between units of electric charge.
Standard unit = Coulomb (C)
|1 abC =
||2.778 * 10-3
||2.998 * 1010
|1 A·h =
||1.079 * 1013
|1 C =
||2.778 * 10-4
||2.998 * 109
|1 statC =
||3.336 * 10-11
||9.266 * 10-14
||3.336 * 10-10
Note: The prefix "ab" is used to indicate an electromagnetic unit in the centimeter-gram-second
The prefix "stat" is used to indicate
an electrical unit in the electrostatic centimeter-gram-second system of units.