The only difference between an amp and a milliamp is that an amp is 1,000 times larger than a milliamp. Both amps and milliamps are metric units used by scientists to measure electrical current, although at different scales.
The amp, also known as the ampere, is the international scientific unit for measuring the electrical charge traveling between two objects. It is one of seven scientific base units and is named after the physicist André-Marie Ampère.
The amp is defined as the amount of constant current that would produce a force equivalent to two times 10 to the negative 7th power Newtons in two conductors spaced 1 meter apart. The milliamp is based on the amp and is exactly one-thousandth of a single amp.