(R) R is a unit to express exposure to radiation (x-rays or gamma rays). 1 R corresponds to the generation of approximately 2.08 x10⁹ ion pairs (1 electrostatic unit of charge) (in 1 cm³ of dry air at 0 °C and 760 torr). 1 R, converted to SI, equals 2.58 x10^-4 coulombs per kg of air.

(V) The SI unit of electric potential.
Definition: The amount of potential energy present per unit of charge. 1 volt represents a potential of 1 joule per coulomb of charge.
The unit is named for the Italian scientist Count Alessandro Volta.