J	=	V RA   =   V (ρLA)/A   =   EL ρL   =   E ρ   =   σE
where:
J	=	current density (joules)
V	=	electric field (volts)
R	=	resistance (ohms)
A	=	area (meters2)
ρ	=	resistivity
L	=	length (meters)
E	=	electric field
σ	=	conductivity