inverse ratio. A ratio of the reciprocals of two quantities.
inverse square law. A law of physics that applies to several natural conditions, such as the strength of a magnetic field, the amount of light falling on a surface, and the intensity of sound pressure. When referring to the strength of a magnetic field, the inverse square law states that the strength of the field varies inversely (the strength decreases as the distance increases) as the square of the distance between the pole and the point at which the strength is measured.
For example, if we double the distance (make it two times as great), the magnetic strength is decreased to a value of one-fourth its original strength. One-fourth is the inverse square of two.
inverse voltage (electrical rectifier). The voltage applied to a rectifier during the half cycle in which it does not conduct.
inversion (meteorology). An increase in temperature with height. An inversion is a reversal of the normal decrease in temperature with height in the troposphere.
inverted engine (reciprocating engine). An in-line or V-type reciprocating engine installed in an aircraft with the crankshaft and crankcase above the cylinders.
inverted spin (aircraft flight maneuver). An acrobatic flight maneuver in which an aircraft spins in an inverted attitude.
inverter (electrical component). An electrical component which changes direct current into alternating current. A rotary inverter is a form of motor-generator unit in which a DC motor drives an AC generator. A static inverter is a solid-state oscillator-amplifier combination.
inverter (logic device). A logic device with one input and one output. The logic state of the output is always opposite that of the input. An inverter is sometimes called a negator, or a NOT function.
invert. To turn something upside down.
iodine. A lustrous, grayish-black, corrosive, poisonous chemical element. Iodine’s symbol is I, its atomic number is 53, and its atomic weight is 126.9044. Iodine is used as a germicide, an antiseptic, and a component in dyes.
ion. An atom with an imbalance between its electrons and its protons. A balanced atom has the same number of protons (positive electrical charges) in its nucleus as it has electrons (negative electrical charges) surrounding the nucleus. If a balanced atom loses an electron, it becomes a positive ion. If it gains an extra electron, it becomes a negative ion.
ion engine. A form of reaction engine that produces forward thrust by the rearward ejection of a stream of ionized particles. Ion engines using ionized particles produced by nuclear reaction have been proposed for space flight.
ionic charges. Electrical charges within a semiconductor diode that result when the mobile charges are pulled away from the PN junction in the diode. When the free electrons in the N-material are drawn away from the junction, a positive ionic charge is left. And when the holes in the P-material are drawn away from the junction, a negative ionic charge is left. It is the ionic charges in a semiconductor diode that produce the barrier voltage.
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