at which (net) charge 
is transferred across that surface. [P4.1, P5.5]
through: a surface
is: the rate at which (net) charge is transferred across that surface. [P4.1, P5.5]
is due: in metallic conductors, to the movement of electrons. In other media, it can be due to the movement of other charged particles (e.g. ions in solution). [P4.1]
has direction: which is defined conventionally as the direction in which positive charge would move, though in many cases the current is actually a flow of negatively-charged particles in the opposite direction. [P4.1]
has as its SI unit: the ampere (A). [P4.1]
Copyright 1997, The Open University