TERMS INDEX

A GUIDE FOR TRICKY TERMS

Ampere / Amperage (amp)

An ampere is a unit of measure of the rate of electron flow or current in an electrical conductor more commonly measured as Amperage in amp. One ampere of current represents one coulomb of electrical charge moving past a specific point in one second.

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dBa / dBA / dB(a)
A-weighted decibels, abbreviated dBA, or dBa, or dB(a), are an expression of the relative loudness of sounds in air as perceived by the human ear. In the A-weighted system, the decibel values of sounds at low frequencies are reduced, compared with unweighted decibels, in which no correction is made for audio frequency. This correction is made because the human ear is less sensitive at low audio frequencies, especially below 1000 Hz, than at high audio frequencies.

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A B C
D E F

Lumen (lm)

The lumen (symbolized lm) is the International Unit of luminous flux. It is defined in terms of candela steradians (cd multiplied by sr). One lumen is the amount of light emitted in a solid angle of 1 sr, from a source that radiates to an equal extent in all directions, and whose intensity is 1 cd.

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Millimeter (mm)

A millimeter (abbreviated as mm and sometimes spelled as millimetre) is a small unit of displacement (length/distance) in the metric system. The metric system, sometimes considered synonymous with the International System of Units, is used throughout the world in the sciences and is the standard of measurement for science engineering, technology and Mathematics.

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G H I J
K L M N

Speed (rpm)

Angular velocity, also called rotational velocity, is a quantitative expression of the amount of rotation that a spinning object undergoes per unit time. It is a vector quantity, consisting of an angular speed component and either of two defined directions or senses.

The magnitude, or length, of the angular velocity vector is directly proportional to the angular speed, and is measured in the same units as angular speed (revolutions per minute – rpm).

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Voltage (V)

Voltage, also called electromotive force, is a quantitative expression of the potential difference in charge between two points in an electrical field.

The greater the voltage, the greater the flow of electrical current (that is, the quantity of charge carriers that pass a fixed point per unit of time) through a conducting or semiconducting medium for a given resistance to the flow. Voltage is symbolised by an uppercase italic letter V or E. The standard unit is the volt, symbolised by a non-italic uppercase letter V.

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O P Q R
S T U V

Watt (W)

The watt (abbreviated W) is the International System of Units’ standard unit of power (energy per unit time), the equivalent of one joule per second. The watt is used to specify the rate at which electrical energy is dissipated, or the rate at which electromagnetic energy is radiated, absorbed, or dissipated.

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W X Y Z