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electron tube

electron tube, device consisting of a sealed enclosure in which electrons flow between electrodes separated either by a vacuum (in a vacuum tube) or by an ionized gas at low pressure (in a gas tube). The two principal electrodes of an electron tube are the cathode and the anode or plate. The simplest vacuum tube, the diode, has only those two electrodes. When the cathode is heated, it emits a cloud of electrons, which are attracted by the positive electric polarity of the anode and constitute the current through the tube. If the cathode is charged positively with respect to the anode, the electrons are drawn back to the cathode. However, the anode is not capable of emitting electrons, so no current can exist; thus the diode acts as a rectifier, i.e., it allows current to flow in only one direction. In the vacuum triode a third electrode, the grid, usually made of a fine wire mesh or similar material, is placed between the cathode and anode. Small voltage fluctuations, or signals, applied to the grid can result in large fluctuations in the current between the cathode and the anode. Thus the triode can act as a signal amplifier, producing output signals some 20 times greater than input. For even greater amplification, additional grids can be added. Tetrodes, with 2 grids, produce output signals about 600 times greater than input, and pentodes, with 3 grids, 1,500 times. X-ray tubes maintain a high voltage between a cathode and an anode. This enables electrons from the cathode to strike the anode at velocities high enough to produce X rays. A cathode-ray tube can produce electron beams that strike a screen to produce pictures, as in some oscilloscopes and older television displays. Gas tubes behave similarly to vacuum tubes but are designed to handle larger currents or to produce luminous discharges. In some gas tubes the cathode is not designed as an electron emitter; conduction occurs when a voltage sufficient to ionize the gas exists between the anode and the cathode. In these cases the ions and electrons formed from the gas molecules constitute the current. Electron tubes have been replaced by solid-state devices, such as transistors, for most applications. However they are still used in high-power transmitters, specialty audio equipment, and some oscilloscopes. A klystron is a special kind of vacuum tube that is a powerful microwave amplifier; it is used to generate signals for radar and television stations.

See also magnetron; photoelectric cell.

The Columbia Electronic Encyclopedia™ Copyright © 2022, Columbia University Press. Licensed from Columbia University Press. All rights reserved.


In wood-frame construction, a horizontal board connecting and terminating posts, joists, or rafters; a timber laid horizontally on the ground to receive other timbers or joists.
Illustrated Dictionary of Architecture Copyright © 2012, 2002, 1998 by The McGraw-Hill Companies, Inc. All rights reserved
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a body having the form of a right prism or right cylinder whose height (thickness) is small compared to the size of the base. Plates are classified according to the shape of the base as rectangular, circular, elliptical, and so on. The plane that divides the thickness of the plate in half is called the medial plane.

Plates are widely used in engineering as elements of many structures and buildings, for example, in walls, floors, ceilings, foundations, bridges, and hydraulic structures. They are elements of ship hulls, aircraft, reservoirs, and many machines and appliances. In acoustics they are used as radiators and receivers of sound and as screens in sound fields.

According to the character of the loads acting on the plate, a distinction is made between plates subject to flexure under transverse loads and plates subject to tension and compression under loads acting in the medial plane.

Flexural deformation causes the points of a plate to be displaced, or deflected, perpendicularly with respect to the medial plane. The surface formed by the points of the medial plane after deformation is called the medial surface. According to the nature of the deformation of the medial surface upon bending, the following types are distinguished: plates that are rigid or experience a small deflection of not more than one-fifth of the thickness; flexible plates, where the deflection is from one-fifth to five times the thickness; and highly flexible plates, or membranes, where the deflection is more than five times the thickness.

In rigid plates the medial layer can without appreciable error be regarded as neutral—that is, as free from tension-compression stresses. Calculations for rigid plates as a rule make use of the hypothesis of straight normals, according to which any straight line that before deformation is normal to the medial plane remains after deformation straight and normal to the medial surface; the length of a fiber in the direction of the thickness of the plate is regarded as unchanged.

In the case of flexible plates in calculations within the limits of elasticity, not only purely bending stresses must be considered but also stresses that are uniformly distributed over the thickness of the plate. The latter are called either membrane stresses or stresses in the medial surface. In highly flexible plates, or membranes, studies of elastic deformations may neglect the flexural stresses proper as compared to the stresses in the medial surface.

When plates are under a load that acts in the medial plane, the stresses are distributed uniformly over the thickness—that is, the plates are under conditions that are more advantageous than in the case of a transverse load. Buckling of the plate, however, is possible in this case, and the plate usually has to be reinforced by a network of stiffeners.

Dynamic problems—the calculation of natural and forced vibrations on plates—are of great importance.


Plates are of interest as oscillatory systems in acoustics. Plates are classified as thin and thick, depending on their thickness compared with the length of the elastic waves in their interior. Transverse (bending) vibrations and longitudinal (extensional) vibrations are possible in thin plates; in the latter case, the displacements are oriented in the plane of the plate. Bending in thin plates is not accompanied by tension of the middle plane; bending and extensional vibrations can therefore exist independently of each other. The situation is different in thick plates. The vibrations of such plates can be represented as a set of longitudinal and shear waves that propagate within the plate and are reflected at its two sides.

In accordance with the two types of oscillations, in a hypothetical infinite plate there can propagate transverse and longitudinal waves. For transverse (flexural) waves, a plate is a system exhibiting dispersion: waves of different wavelengths propagate in the plate with different speeds. The speed of longitudinal waves in a thin plate is independent of the wavelength. Plates of limited size have discrete sets of natural frequencies. To each natural frequency there corresponds a natural vibration form, which can be pictorially represented by a distribution of nodal lines, where the displacements during the vibration process are equal to zero. The natural frequencies and forms of the vibrations depend on the size and shape of the plate and on the conditions of support of the plate’s edges. A vibrating plate is itself a source of vibrations in the medium in which it is located. The radiation efficiency of a plate depends on the elastic properties and density of the plate material and on the properties of the medium in which the plate is located.


Bubnov, I. G. Trudy po teorii plastin. Moscow, 1953.
Timoshenko, S. P. Plastinki i obolochki, Moscow-Leningrad, 1948. (Translated from English.)
Vol’mir, A. S. Gibkie plastinki i obolochki. Moscow, 1956.
Vol’mir, A. S. Nelineinaia dinamika plastinok i obolochek. Moscow, 1972.
Strutt, J. (Lord Rayleigh). Teoriia zvuka, 2nd ed., vol. 1. Moscow, 1955. (Translated from English.)
Skudrzyk, E. Osnovy akustiki, vol. 2. Moscow, 1959. (Translated from German.)
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

What does it mean when you dream about a plate?

A plate contains nourishment, so dreaming about a plate can refer metaphorically to how we nourish our emotional life. An empty plate can thus mean that our needs are not being fulfilled. If the plate is overly full, it could be alluding to the expression about being overly busy, having a “full plate.”

The Dream Encyclopedia, Second Edition © 2009 Visible Ink Press®. All rights reserved.


(building construction)
A shoe or base member, such as of a partition or other kind of frame.
The top horizontal member of a row of studs used in a frame wall.
(design engineering)
A rolled, flat piece of metal of some arbitrary minimum thickness and width depending on the type of metal.
One of the conducting surfaces in a capacitor.
One of the electrodes in a storage battery.
A smooth, thin, flat fragment of rock, such as a flagstone.
A large rigid, but mobile, block involved in plate tectonics; thickness ranges from 30 to 150 miles (50 to 250 kilometers) and includes both crust and a portion of the upper mantle.
(graphic arts)
In etching, the piece of copper, zinc, or other metal that constitutes the base from which prints are made.
In photography, a sheet of glass coated with a sensitized emulsion.
In printing, the reproduction of type or cuts in metal or other material; a plate may bear a relief, intaglio, or planographic printing surface.
A thick flat particle of metal powder.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


1.beneath a row of studs.


plate, 2
1. A thin, flat sheet of material.
2. In wood frame construction, a horizontal board or timber connecting and terminating posts, joists, rafters, etc.
3. A timber laid horizontally (and on its widest side) in a wall or on top of a wall or on the ground to receive other timbers or joists. Also See ground plate, wall plate, partition plate, pole plate, sill plate.
4. Plated metalware.
5. A flat, rolled-metal product having the following dimensions: hot-rolled steel, minimum thickness 0.18 in. (0.46 cm) and a width exceeding 6 in. (15.2 cm); stainless steel, minimum thickness 3/16 in. (0.48 cm) and a width exceeding 10 in.(25.4 cm); aluminum, minimum thickness 0.25 in. (0.64 cm), no minimum width specified; copper alloys, thickness exceeding 3/16 in. (0.48 cm) and a width greater than 12 in. (30.5 cm). Also See crown plate, curtail plate, false plate, gallery plate, head plate, pole plate, rafter plate, raising plate, roof plate, sill, sill plate, soleplate, top plate, wall plate.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.


1. any shallow or flat receptacle, esp for receiving a collection in church
2. flat metal of uniform thickness obtained by rolling, usually having a thickness greater than about three millimetres
3. a thin coating of metal usually on another metal, as produced by electrodeposition, chemical action, etc.
4. Photog
a. a sheet of glass, or sometimes metal, coated with photographic emulsion on which an image can be formed by exposure to light
b. (as modifier): a plate camera
5. an orthodontic device, esp one used for straightening children's teeth
6. an informal word for denture
7. Anatomy any flat platelike structure or part
8. any of the rigid layers of the earth's lithosphere of which there are believed to be at least 15
9. Electronics
a. Chiefly US the anode in an electronic valve
b. an electrode in an accumulator or capacitor
10. a light horseshoe for flat racing
11. See plate rail
12. RC Church a flat plate held under the chin of a communicant in order to catch any fragments of the consecrated Host
13. Archaic a coin, esp one made of silver
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
fornicatus: absence of microsetae type 1 entirely covering ventral surface of ventral plate; macroseta B very large and inserted laterally; ventral process of stylus as a spiny cone; rectangular ventral plate; apophyses of coxa IV of male short and directed backwards; and scutal area III without armature.
Abdominal ventral plates present on abdominal segments 5-8, covered by comb-like projections (Fig.
Also within the ventral plate are occasional cells having dark-staining cytoplasmic inclusions.
Ventral plate, aspect (presence ofa deep cleft), (0) entire (without any cleft) (Maury & Roig-Alsina 1985:fig.
Schizosteus) possessed rooted unnamed plates and tesserae showing a synchronomorial type of growth in the vicinity and on the margins of dorsal and ventral plates (Halstead Tarlo 1964, p.
8 Basis capituli rectangular dorsally, ventral plates absent in , both, ornate or Inornate .....................
Ventral genital plates moderately sclerotized, nearly symmetrical, ovate, with round process on the inner apical margin and long process on the outer apical margin angled toward midline; dorsal genital plates small, weakly sclerotized, partially covered by ventral plates. Total body length: 19.3 mm.

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