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Usage of N⋅m is discouraged by the SI authority, since it can lead to confusion as to whether the quantity expressed in newton-metres is a torque measurement, or a measurement of work. [15] Another unit for work is the foot-pound, which comes from the English system of measurement. As the unit name suggests, it is the product of pounds for ...
Energy is defined via work, so the SI unit of energy is the same as the unit of work – the joule (J), named in honour of James Prescott Joule [1] and his experiments on the mechanical equivalent of heat. In slightly more fundamental terms, 1 joule is equal to 1 newton metre and, in terms of SI base units
This is the definition declared in the modern International System of Units in 1960. [13] The definition of the joule as J = kg⋅m 2 ⋅s −2 has remained unchanged since 1946, but the joule as a derived unit has inherited changes in the definitions of the second (in 1960 and 1967), the metre (in 1983) and the kilogram . [14]
The erg is a unit of energy equal to 10 −7 joules (100 nJ). It is not an SI unit, instead originating from the centimetre–gram–second system of units (CGS). Its name is derived from ergon (ἔργον), a Greek word meaning 'work' or 'task'. [1] An erg is the amount of work done by a force of one dyne exerted for a distance of one centimetre.
The atomic units have been chosen to use several constants relating to the electron: the electron mass, the elementary charge, the Coulomb constant and the reduced Planck constant. The unit of energy in this system is the total energy of the electron in the Bohr atom and called the Hartree energy. The unit of length is the Bohr radius.
Thermodynamic work is one of the principal kinds of process by which a thermodynamic system can interact with and transfer energy to its surroundings. This results in externally measurable macroscopic forces on the system's surroundings, which can cause mechanical work, to lift a weight, for example, [1] or cause changes in electromagnetic, [2] [3] [4] or gravitational [5] variables.
Power is the rate with respect to time at which work is done; it is the time derivative of work: =, where P is power, W is work, and t is time. We will now show that the mechanical power generated by a force F on a body moving at the velocity v can be expressed as the product: P = d W d t = F ⋅ v {\displaystyle P={\frac {dW}{dt}}=\mathbf {F ...
The SI unit of work per unit charge is the joule per coulomb, where 1 volt = 1 joule (of work) per 1 coulomb of charge. [citation needed] The old SI definition for volt used power and current; starting in 1990, the quantum Hall and Josephson effect were used, [10] and in 2019 physical constants were given defined values for the definition of all SI units.