The ampere is the SI unit of electric current
The ampere, or 'amp' for short, measures electric current, which is a flow of electrons along a wire or ions in an electrolyte, as in batteries. Electric current allows us to power electrical devices, like smartphones or laptops and can even be used to operate a bus or car.
The ampere has only been in use for as long as we have had access to electricity – a small proportion of the history of measurement. The ampere definition exploits the fact that electric current is made up of a flow of billions of identical charged particles called electrons. We can create a standard ampere by using special nano‑scale electric circuits that control the flow of electrons.