Engineering

Biofuel (biomass fuel)

Biomass fuels are exclusively combustion fuels and when they are burnt they generate carbon dioxide that enters the atmosphere in exactly the same way as fossil fuel would generate carbon dioxide. Biomass fuel is biomass converted directly to energy or converted to liquid or gaseous fuels such as ethanol, methanol, methane, and hydrogen.

Lubricant

A lubricant is an organic or synthetic substance (it can occur in any physical state: liquid, solid, gaseous and even semi-solid or viscous) which has the property of reducing the friction between surfaces in contact under any operating condition, dissipating the heat generated during the relative movement between the surfaces, maintaining its chemical stability, protecting the mechanical parts from corrosive attacks, cushioning possible shocks, …

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Response time

Response time is the time required by a measuring instrument or system to settle to its final steady position after the application of the input. For a step input function, the response time may be defined as the time taken by the instrument to settle to a specified percentage of the quantity being measured, after …

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Ampere (unit of electric current)

Electric units, called “international units,” for current and resistance, were introduced by the International Electrical Congress held in Chicago in 1893, and definitions of the “international ampere” and “international ohm” were confirmed by the International Conference in London in 1908. Although it was already obvious on the occasion of the 8th CGPM (1933) that there …

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Direct current (DC)

Direct current (DC) is electricity flowing in a constant direction. So, electrons always flow constantly in the same direction within the electrical circuit, and/or possessing a voltage with constant polarity, therefore they will always circulate in the same direction. Direct current was produced in 1800 by Italian physicist Alessandro Volta’s battery, by his “Voltaic pile.” Direct …

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Alternating current (AC)

Alternating current describes the flow of charge that changes direction periodically. As a result, the voltage level also reverses along with the current. In other words, it is a type of electric current characterized by the fact of inverting the electric polarity continuously over time. Basically, unlike the direct current, in which the polarity is fixed …

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Overcurrent

In an electric power system, overcurrent or excess current is a situation where a larger than intended electric current exists through a conductor, leading to excessive generation of heat, and the risk of fire or damage to equipment. There are two types of overcurrents: overload currents; short-circuit currents. Possible causes for overcurrent include short circuits, excessive load, …

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Wave impedance

The wave impedance of an electromagnetic wave is the ratio of the transverse components of the electric and magnetic fields (the transverse components being those at right angles to the direction of propagation). If the electric field strength is expressed in volts per meter and the magnetic field strength is expressed in ampere-turns per meter, the wave …

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Mechanical impedance

Mechanical impedance is a measure of how much a structure resists motion when subjected to a harmonic force. It relates forces with velocities acting on a mechanical system. The mechanical impedance of a point on a structure is the ratio of the force applied at a point to the resulting velocity at that point.

Electrical impedance

Electrical impedance is a physical quantity that represents the opposition force of a circuit to the passage of alternating electric current, or, more generally, of a variable current. In other words, is the amount of opposition that an electrical element offers to current flow in a circuit when a voltage is applied at a specific frequency. …

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