The ampere (
SI
unit symbol: A), often
shortened to "amp",^{
[1]} is the SI unit of
electric current^{
[2]}^{
[3]} (
dimension symbol: I)^{
[4]} and is one of the seven^{
[5]}
SI base units. It is named after
André-Marie Ampère (1775–1836), French mathematician and physicist, considered the father of
electrodynamics.
The ampere is equivalent to one
coulomb (roughly 7018624200000000000♠6.242×10^{18} times the
elementary charge) per second.^{
[6]} Amperes are used to express flow rate of electric charge. For any point experiencing a current, if the number of charged particles passing through it — or the charge on the particles passing through it — is increased, the amperes of current at that point will proportionately increase.
The ampere should not be confused with the
coulomb (also called "ampere-second") or the
ampere hour (A⋅h). The ampere is a unit of current, the amount of charge transiting per unit time, and the coulomb is a unit of
charge. When
SI units are used, constant, instantaneous and average current are expressed in amperes (as in "the charging current is 1.2 A") and the charge accumulated, or passed through a circuit over a period of time is expressed in coulombs (as in "the
battery charge is 7004300000000000000♠30000 C"). The relation of the ampere (C/s) to the coulomb is the same as that of the
watt (J/s) to the
joule.