Energy

Energy is a physical quantity and describes the ability of a body to perform work. In the technical sense, heat energy, work and energy are three entities of the same nature, defined by the same unit: Joule (1 J = 1 Nm = 1 Ws). Thermal energy is commonly specified in Joules (J), mechanical energy in Newton metres (Nm) and electrical energy in Watt seconds (Ws). A fourth unit, the rarely used electron volt (eV), is the unit of energy used for atomic physics.