Electrical current is measured in amperes. The unit symbol for ampere is "A," without the quotes. The dimension symbol for electrical current is "I," also without the quotes. Therefore, "I = 3 A" means the electrical current is 3 amperes.
A current of 1 ampere means that there is one coulomb of charge passing through a wire every second. Ampere is one of the International System of Units base units, meaning other SI units of measurement are derived from it. For example, the coulomb, with a unit symbol of "C," is a unit of electrical charge and can be mathematically expressed as "1 C = 1 A * 1 s."