What is current how it is measured?

An electric current (symbol: I) is a very slow drift of charge carriers (electrons, in metallic conductors), and is measured in amperes (symbol: A). An ampere is defined in terms of the 'magnetic effect' of an electric current, that is the force of attraction or repulsion between two, parallel, conductors due to the interaction of their magnetic fields. An instrument used to measure electric current is called an 'ammeter'.