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arc (in electricity)

arc, in electricity, highly luminous and intensely hot discharge of electricity between two electrodes. The arc was discovered early in the 19th cent. by the English scientist Sir Humphry Davy, who so named it because of its shape. An arc is characterized by a high current, low voltage, and indefinite duration. It is usually started when two electrodes carrying an electric current are drawn apart. At the instant the electrodes are parted, strong electric forces draw electrons from one electrode to the other, initiating the arc. The discharge consists of a current composed of these electrons and charged gas particles, called ions, that form between the electrodes. The first practical electric light, the arc lamp, made use of the arc formed between two carbon rods (see lighting). Today the use of the arc lamp is limited to special purposes, e.g., in searchlights and in research applications. The principle of the electric arc is employed in welding (as in the hydrogen arc, where hydrogen is introduced between tungsten electrodes) and also in generating heat in the electric furnace. A spark, like an arc, is a discharge of electricity between two points, but it has a high voltage and a short duration. Lightning is an example of a spark.

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arc

arc / ärk/ • n. 1. a part of the circumference of a circle or other curve. ∎  a curved shape, or something shaped like a curve: the arc of the sky. ∎  a curving trajectory: he swung his flashlight in an arc. ∎  [as adj.] Math. indicating the inverse of a trigonometrical function. 2. (also electric arc) a luminous electrical discharge between two electrodes or other points. • v. (arced ; arc·ing ) [intr.] 1. move with a curving trajectory: the ball arced across the room. 2. [usu. as n.] (arcing) form an electric arc: check that switches operate properly with no sign of arcing. PHRASES: minute of arcsee minute1 (sense 2). second of arcsee second2 (sense 2).

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arc (in geometry)

arc, in geometry, a curved line or any part of it; in particular, a portion of the circumference of a circle. The length s of an arc of a circle of radius r and subtending a central angle of θ radians is s=rθ; if θ is measured in degrees, then the arc is given by s=2πrθ/360.

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arc

arc Portion of a curve. For a circle, the length (s) of an arc is found either by 2rπ × θ/360 or the product of the radius (r) and the angle (θ), measured in radians, that it subtends at the centre: that is, s = r θ.

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ARC

ARC / ärk/ • abbr. ∎  Med. AIDS-related complex. ∎  American Red Cross.

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arc

arc XIV. — (O)F. :- L. arcus bow, arch.

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ARC

ARC n. AIDS-related complex: see AIDS.

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arc

arc of a graph. See graph.

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arc

arc See ISLAND ARC.

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arc

arcarc, ark, Bach, bark, barque, Braque, Clark, clerk, dark, embark, hark, impark, Iraq, Ladakh, Lamarck, lark, macaque, marc, mark, marque, narc, nark, Newark, park, quark, sark, shark, snark, spark, stark, Vlach •matriarch, patriarch •tanbark • ringbark • stringy-bark •Offenbach • ironbark • oligarch •salesclerk • titlark • skylark •meadowlark • woodlark • mudlark •landmark • checkmark • Denmark •benchmark • waymark • trademark •seamark • Bismarck • telemark •tidemark • Kitemark • pockmark •Ostmark • hallmark • Goldmark •Deutschmark • bookmark • footmark •earmark • watermark • birthmark •anarch • car park • skatepark •ballpark •Petrarch, tetrarch •hierarch, squirearch •exarch • Pesach • loan shark •Plutarch • aardvark

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Arc

Arc

In Euclidean geometry, an arc is a segment of a curve, most often a circle, in a two-dimensional plane. When it is a circle, the arc is called a circular arc. In the strictest definition, an arc is a segment of a curve in a plane. Examples include segments of geometrical forms such as circles, ellipses, and parabolas, as well as irregular arcs defined by analytical functions.

Arcs of circles can be classified by size. A minor arc is one whose length is shorter than one-half of the circumference of a circle. A major arc is one whose length is longer than one-half of the circumference of a circle. An arc whose length is exactly one-half of the circumference of the circle is simply called a semi-circle. The line connecting the endpoints of a major arc or minor arc is called a chord.

Angles subtended by circles can be classified by the location of the vertex. One important type of angle has the vertex located at the circumference. An angle whose vertex is at the center of the circle is called a central angle. Each specific central angle is subtended by only one arc, but each arc subtends infinitely many angles.

KEY TERMS

Circumference The line defined by the collection of points at a distance r from the center of a circle.

Subtend Intersect.

Vertex The point at which the two sides of an angle meet.

An arc of a circle can be measured by length along the circumference or in terms of the angle subtended by the arc. A theorem of geometry states that the measure of the central angle of the circle is the measure of corresponding arc. If the arc lies on a circle of radius (r ) and subtends a central angle (A) measured in degrees, then the length of the arc is given by b = 2π r (A/360), where π is the mathematical constant 3.14159, defined as the ratio of the circles circumference to its diameter.

In the case of irregular arcs, lengths are more complicated to determine. Historically, only approximations were possible by mathematicians. The rectification of a curve, or calculating the length of an irregular arc, can be performed, as noted during the seventeenth century, with the use of calculus and differential geometry.

Kristin Lewotsky

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Arc

Arc

An arc is a segment of a curve , most often a circle . In the strictest definition, an arc is a segment of a curve in a plane . Examples include segments of geometrical forms such as circles, ellipses, and parabolas, as well as irregular arcs defined by analytical functions.

Arcs of circles can be classified by size. A minor arc is one whose length is shorter than one-half of the circumference of a circle. A major arc is one whose length is longer than one half of the circumference of a circle. An arc whose length is exactly one-half of the circumference of the circle is simply called a semi-circle. The line connecting the endpoints of a major arc or minor arc is called a chord.

Angles subtended by circles can be classified by the location of the vertex. One important type of angle has the vertex located at the circumference. An angle whose vertex is at the center of the circle is called a central angle. Each specific central angle is subtended by only one arc, but each arc subtends infinitely many angles.

An arc of a circle can be measured by length along the circumference, or in terms of the angle subtended by the arc. A theorem of geometry states that the measure of the central angle of the circle is the measure of corresponding arc. If the arc lies on a circle of radius r and subtends a central angle (LA) measured in degrees, then the length of the arc is given by b = 2πr(LA/360).

In the case of irregular arcs, the length can be determined using calculus and differential geometry.

Kristin Lewotsky

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Circumference

—The line defined by the collection of points at a distance r from the center of a circle.

Subtend

—Intersect.

Vertex

—The point at which the two sides of an angle meet.

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Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.