direct current

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direct current,

abbr. DC, a movement of electric charge across an arbitrarily defined surface in one direction only. See electricityelectricity,
class of phenomena arising from the existence of charge. The basic unit of charge is that on the proton or electron—the proton's charge is designated as positive while the electron's is negative.
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; generatorgenerator,
in electricity, machine used to change mechanical energy into electrical energy. It operates on the principle of electromagnetic induction, discovered (1831) by Michael Faraday.
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The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Direct Current

 

an electric current whose magnitude and direction do not change with time. It arises under the action of a direct voltage and can exist only in a closed circuit. In a nonbranching circuit the magnitude of a direct current is the same for all cross sections of the circuit. The principal laws governing direct currents are Ohm’s law, which gives the relationship between voltage and current, and Joule’s law, which defines the quantity of heat produced by a current flowing through a conductor. Calculations of networks of conductors carrying a direct current are made with the aid of Kirchhoff’s laws.

In engineering, equipment in which the current is unidirectional is regarded as DC equipment even if the magnitude of the current varies.

Rotating-machine generators are high-power sources of direct current. Direct current can also be obtained by the rectification of alternating current. Low-power sources of direct current include galvanic cells, thermocouples, and photoelectric cells; groups of such cells are called batteries—for example, solar batteries. Rotating electric machines are also used as low-power sources. Magnetohydrodynamic generators are a new, high-efficiency source of direct current. Storage batteries, which can be recharged, are a secondary source of direct current.

Low-voltage direct current finds application in many branches of industry. In electrometallurgy, for example, it is used in such processes as the melting and electrolysis of ores, primarily aluminum ores. Direct current is used in transport-vehicle traction motors and in electric drives requiring variable-speed motors with a large overload capacity where the speed can be smoothly and economically regulated within wide limits. Communication, automation, signaling, and remote-control systems often run on DC power. The use of direct current for the transmission of electric power over distances in excess of 1,000 km shows promise. Work is being done on DC power transmission with practically no losses over superconducting lines.

REFERENCES

Polivanov, K. M. Lineinye elektricheskie tsepi s sosredotochennymi postoiannymi. Moscow, 1972. (Teoreticheskie osnovy elektrotekhniki, vol. 1.)
Kasatkin, A. S. Elektrotekhnika, 3rd ed. Moscow, 1973.

A. S. KASATKIN

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

direct current

[də¦rekt ′kə·rənt]
(electricity)
Electric current which flows in one direction only, as opposed to alternating current. Abbreviated dc.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

Direct current

Electric current which flows in one direction only through a circuit or equipment. The associated direct voltages, in contrast to alternating voltages, are of unchanging polarity. Direct current corresponds to a drift or displacement of electric charge in one unvarying direction around the closed loop or loops of an electric circuit. Direct currents and voltages may be of constant magnitude or may vary with time.

Direct current is used extensively to power adjustable-speed motor drives in industry and in transportation. Very large amounts of power are used in electrochemical processes for the refining and plating of metals and for the production of numerous basic chemicals.

Direct current ordinarily is not widely distributed for general use by electric utility customers. Instead, direct-current (dc) power is obtained at the site where it is needed by the rectification of commercially available alternating-current (ac) power to dc power. See Direct-current transmission, Electric power systems

McGraw-Hill Concise Encyclopedia of Engineering. © 2002 by The McGraw-Hill Companies, Inc.

direct current

In an electric circuit, a current that flows in one direction only. Also see alternating current.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.

direct current

a continuous electric current that flows in one direction only, without substantial variation in magnitude
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

DC

(1) (Direct Current) An electrical current that travels in one direction and used within the computer's electronic circuits. Contrast with AC.

(2) (Data Communications) See DB/DC.

(3) (Domain Controller) See PDC and BDC.
Copyright © 1981-2019 by The Computer Language Company Inc. All Rights reserved. THIS DEFINITION IS FOR PERSONAL USE ONLY. All other reproduction is strictly prohibited without permission from the publisher.
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A national direct-current grid could also help lower emissions to as much as 80 percent below 1990 levels within 15 years, all with commercially available technology and without increasing the costs of electricity, according to a study published earlier in Nature Climate Change.
In this section, a novel PIPSO based approach is presented in designing the PI controller gain variables for the proposed direct-current vector controlled system [16-18].
The use of the DRUs and the encapsulated DC-CS direct-current switchgear decreases the installation space by more than 80 percent compared with air-insulated technology.
Fridriksson, "Using transcranial direct-current stimulation to treat stroke patients with aphasia," Stroke, vol.
Based on the findings, Schiff has obtained approval from his medical center to begin limited testing of steady, direct-current electric fields on humans.
Direct-current motors have been popular since they displaced steam engines as a source of train propulsion in the 1940s.
Developing the grid using high-voltage direct-current (HVDC) transmission technology with overhead power lines and gas-insulated DC transmission lines buried underground over certain sections could be implemented using considerably less resources than three-phase technology.
The line includes manual and direct-current auto-iris models for 1/3" and 1/4" color and black-and-white cameras.
The company noted that the E8 generator is capable of delivering 48 volts of direct-current electricity at 50 amperes of current.
Using some fancy statistical footwork, the reserachers separated out the direct-current (DC) component due to core currents from the tangle of alternating-current (AC) signals arising from a variety of sources, such as the erratic flow of ions in the ionosphere, that induce currents in the earth.

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