SI base unit SI base unit The International System of Units (SI) defines seven units of measure as a basic set from which all other SI units can be derived. The SI base units and their physical quantities are the meter for measurement of length, the kilogram for mass, the second for time, the ampere for electric current, the kelvin for temperature, the candela for luminous intensity, and the mole for amount of substance. The SI base units form a set of mutually independent dimensions as required by dimensional analysis commonly employed in science and technology. The names and symbols of SI base
Current density of the unit vectors. That is, the component of current density passing through the surface (i.e. normal to it) is , while the component of current density passing tangential to the area is , but there is "no" current density actually passing "through" the area in the tangential direction. The "only" component of current density passing normal to the area is the cosine component. Current density is important to the design of electrical and electronic systems. Circuit performance depends strongly upon the designed current level, and the current density then is determined by the dimensions of the conducting elements. For