Gauge - Definition and Overview

Gauge (sometimes spelled gage) vb. Means to 'measure exactly.' It can refer to any type of measuring device.

It has various different meanings in mechanics, engineering, mathematics physics, and jewellery.

• In mechanics, a pressure gauge is a device for indicating liquid or gas pressure. It is commonly used to refer to other sensors such as a temperature gauge, level gauge, strain gauge etc.

• Gauge is commonly used in the context of railways, where "track or Rail gauge" means the distance between the inside edges of the two rails forming the track (eg standard gauge, narrow gauge) and "loading gauge" refers to the set of height and width profiles governing the maximum dimensions of railway vehicles.

• In engineering, gauge refers to a measure of width or thickness, or to devices used to make measurements eg. Feeler gauges (originally of width or thickness). It can also be used as a verb to describe the act of taking a measurement, typically an estimate.

• In metal sheeting, it refers to the thickness of the sheet.

• In electricity, gauge refers to the size of the conductors used to carry electric current. In the U.S., small wire gauges are referred to using the American wire gauge where 40-gauge wire is very small and 0000 ("Four-Oh") wire is the largest common size. Larger sizes of wires are referred to by their size in "Mean Circular Mils". In the rest of the world, wire guages are referred to by their cross-section in mm².

• In jewellery, especially as applied to body piercing, gauge refers to the thickness of the metal that penetrates the body tissue. As a point of reference, the holes in pierced ears normally exhibit diameters of 20 or 18 gauge. with wire gauge measurements, the smaller the gauge number, the larger the diameter.

• Media:Gauge_Chart.pdf Chart comparing all known wire gauges to each other

• In shotguns, "gauge" is a term related to the diameter (caliber) of the barrel. The gauge is determined by the number of solid spheres of a diameter equal to the inside diameter of the barrel that could be made from a pound of lead. The term bore is also used for this, especially in British English. It is more rarely used to refer to the internal dimensions of a cannon.

• In mathematics and physics, a gauge transformation is a member of a group of mappings to a space or a spacetime, where this group of mappings satisfies certain properties. The actions of bosons, which mediate interactions between fermions, in the theories of the electroweak interaction and quantum chromodynamics of the Standard Model of particle physics, are invariant under gauge transformations, so these bosons are called gauge bosons. Gauge theories in physics postulate that symmetry transformations can only be performed locally.

• Gauge is also the stage name of an actress in adult films.