Current density Current density In electromagnetism, current density is the electric current per unit area of cross section. The current density vector is defined as a vector whose magnitude is the electric current per cross-sectional area at a given point in space, its direction being that of the motion of the charges at this point. In SI units, the electric current density is measured in amperes per square metre. Assume that "A" (SI unit: m) is a small surface centred at a given point "M" and orthogonal to the motion of the charges at "M". If "I" (SI unit: A) is the
Rad (unit) its use for "public health ... purposes" be phased out by 31 December 1985. The following table shows radiation quantities in SI and non-SI units: Rad (unit) The rad is a unit of absorbed radiation dose, defined as 1 rad = 0.01 Gy = 0.01 J/kg. It was originally defined in CGS units in 1953 as the dose causing 100 ergs of energy to be absorbed by one gram of matter. It has been replaced by the gray (Gy) in SI derived units but is still used in the United States, though "strongly discouraged" in the chapter 5.2 of style