The unit of electric current is Ampere (= coulomb/sec) and that of the current density is A/m . For a thin wire with a small cross sectional area, the current density may be taken as uniform. In this case,
where is the component of the area vector parallel to the direction of current.
. For a thin wire with a small cross sectional area, the current density 
may be taken as uniform. In this case, 
is the component of the area vector parallel to the direction of current. 
