MOVEMENT OF CHARGE:
Although electric current is referred to as the flow of electrons through a conductor, it should be noted that more exactly, any movement of electric charge constitutes an electric current. Thus, passage of electricity may occur through a:
• conductor such as metal, due to the movement of the loosely held outer electrons of the atoms.
• vacuum or gas, due to the movement of electrons.
• gas, due to the movement of the ionised gas molecules.
• liquid, due to the ionisation of certain molecules, particularly those of acids and salts in solution (e.g. Electrolytes).
The ampere may be defined in terms of the mechanical units of force and length, a more helpful picture is that of moving electrons. When a current of one ampere is flowing in a conductor, one coulomb of charge passes any point in the conductor every second.
The ampere is thus a measure if the rate of flow of electrons.