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A unit of electrical energy, particularly for utility bills, is the kilowatt-hour (kWh); [3] one kilowatt-hour is equivalent to 3.6 megajoules. Electricity usage is often given in units of kilowatt-hours per year or other periods. [4] This is a measurement of average power consumption, meaning the average rate at which energy is transferred ...
The joule (/ dʒ uː l / JOOL, or / dʒ aʊ l / JOWL; symbol: J) is the unit of energy in the International System of Units (SI). [1] It is equal to the amount of work done when a force of one newton displaces a mass through a distance of one metre in the direction of that force.
As a result, an increase in the rate of oxygen consumption is representative of an increase in energy expenditure. VO2 is often measured in absolute terms (ex. Liters/min), but in weight bearing activities, such as running, body mass can have a profound influence on energy expenditure. As a result, it is common to express energy expenditure as ...
Thomas Young, the first person to use the term "energy" in the modern sense. The word energy derives from the Ancient Greek: ἐνέργεια, romanized: energeia, lit. 'activity, operation', [4] which possibly appears for the first time in the work of Aristotle in the 4th century BC. In contrast to the modern definition, energeia was a ...
Specific mechanical energy, rather than simply energy, is often used in astrodynamics, because gravity changes the kinetic and potential specific energies of a vehicle in ways that are independent of the mass of the vehicle, consistent with the conservation of energy in a Newtonian gravitational system.
Energy conversion efficiency depends on the usefulness of the output. All or part of the heat produced from burning a fuel may become rejected waste heat if, for example, work is the desired output from a thermodynamic cycle. Energy converter is an example of an energy transformation.
Energy quality is a measure of the ease with which a form of energy can be converted to useful work or to another form of energy: i.e. its content of thermodynamic free energy. A high quality form of energy has a high content of thermodynamic free energy, and therefore a high proportion of it can be converted to work; whereas with low quality ...
Electrical energy is energy related to forces on electrically charged particles and the movement of those particles (often electrons in wires, but not always). This energy is supplied by the combination of current and electric potential (often referred to as voltage because electric potential is measured in volts) that is delivered by a circuit (e.g., provided by an electric power utility).