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Encyclopedia > Direct current

Direct current (DC or "continuous current") is considered as the constant flow of electrons in the single direction from low to high potential. This is typically in a conductor such as a wire, but can also be through semiconductors, insulators, or even through a vacuum as in electron or ion beams. In direct current, the electric charges flow in the same direction, distinguishing it from alternating current (AC). A term formerly used for direct current was Galvanic current. In electricity, current refers to electric current, which is the flow of electric charge. ... Properties The electron (also called negatron, commonly represented as e−) is a subatomic particle. ... Electric potential is the potential energy per unit of charge associated with a static (time-invariant) electric field, also called the electrostatic potential, typically measured in volts. ... In science and engineering, conductors are materials that contain movable charges of electricity. ... A semiconductor is a solid whose electrical conductivity can be controlled over a wide range, either permanently or dynamically. ... This article or section is in need of attention from an expert on the subject. ... Look up Vacuum in Wiktionary, the free dictionary. ... A charged particle beam is a group of electrically charged particles that have approximately the same kinetic energy and move in approximately the same direction. ... Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ... City lights viewed in a motion blurred exposure. ... In language, an archaism is the deliberate use of an older form that has fallen out of current use. ...

Types of direct current
Types of direct current

Long after the usage of this term had been established, physicists realized that electrons actually flow to a negative potential (pole) and so-called "holes" flow to the opposite one. However, the established usage of the term prevailed. Image File history File links TypesOfDirectCurrentDiagram. ... Image File history File links TypesOfDirectCurrentDiagram. ... Properties The electron (also called negatron, commonly represented as e−) is a subatomic particle. ...


The first commercial electric power transmission (developed by Thomas Edison in the late nineteenth century) used direct current. Because of the advantage of alternating current over direct current in transforming and transmission, electric power distribution today is nearly all alternating current. See War of Currents. Power line redirects here. ... Thomas Alva Edison (February 11, 1847 – October 18, 1931) was an American inventor and businessman who developed many devices which greatly influenced life worldwide into the 21st century. ... Alternative meaning: Nineteenth Century (periodical) (18th century — 19th century — 20th century — more centuries) As a means of recording the passage of time, the 19th century was that century which lasted from 1801-1900 in the sense of the Gregorian calendar. ... In the War of Currents era in the late 1880s, George Westinghouse and Thomas Edison became adversaries due to Edisons promotion of direct current (DC) for electric power distribution over the alternating current (AC) advocated by Westinghouse and Nikola Tesla. ...

Contents

Various definitions

Within Electrical Engineering, the term DC is a synonym for constant. For example, the voltage across a DC voltage source is constant as is the current through a DC current source. The DC solution of an electric circuit is the solution where all voltages and currents are constant. It can be shown that any voltage or current waveform can be decomposed into a sum of a DC component and a time-varying component. The DC component is defined to be the average value of the voltage or current over all time. The average value of the time-varying component is zero. Electrical Engineers design power systems… … and complex electronic circuits. ... A voltage source is any device or system that produces an electromotive force between its terminals OR derives a secondary voltage from a primary source of the electromotive force. ... An ideal current source, I, driving a resistor, R, and creating a voltage V A current source is an electrical or electronic device that delivers or absorbs electric current. ... An electrical network or electrical circuit is an interconnection of analog electrical elements such as resistors, inductors, capacitors, diodes, switches and transistors. ...


Although DC stands for "Direct Current", DC sometimes refers to "constant polarity." With this definition, DC voltages can vary in time, such as the raw output of a rectifier or the fluctuating voice signal on a telephone line.


Some forms of DC (such as that produced by a voltage regulator) have almost no variations in voltage, but may still have variations in output power and current. A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level. ... International safety symbol Caution, risk of electric shock (ISO 3864), colloquially known as high voltage symbol. ... For delivered electrical power, see Electrical power industry. ...


Applications

Direct current installations usually have different types of sockets, switches, and fixtures, mostly due to the low voltages used, from those suitable for alternating current. It is usually important with a direct current appliance not to reverse polarity unless the device has a diode bridge to correct for this. (Most battery-powered devices do not.) A socket generally designates a cavity or region used for fitting and connecting some specific device. ... Electrical switches. ... In the law of real property, fixtures are anything that would otherwise be a chattel that have, by reason of incorporation or affixation, become permanently attached to the real property. ... Three bridge rectifiers. ...


High voltage direct current is used for long-distance point-to-point power transmission and for submarine cables, with voltages from a few kilovolts to approximately one megavolt. HVDC or high-voltage, direct current electric power transmission systems contrast with the more common alternating-current systems as a means for the bulk transmission of electrical power. ... Submarine power cables are cables for electrical power running through the sea, below the surface. ...

This symbol is found on many electronic devices that either require or produce direct current
This symbol is found on many electronic devices that either require or produce direct current

DC is commonly found in many low-voltage applications, especially where these are powered by batteries, which can produce only DC, or solar power systems, since solar cells can produce only DC. Most automotive applications use DC, although the alternator is an AC device which uses a rectifier to produce DC. Most electronic circuits require a DC power supply. Applications using fuel cells (mixing hydrogen and oxygen together with a catalyst to produce electricity and water as byproducts) also produce only DC. Image File history File links DCCurrent. ... Image File history File links DCCurrent. ... International safety symbol Caution, risk of electric shock (ISO 3864), colloquially known as high voltage symbol. ... Four double-A (AA) rechargeable batteries In science and technology, a battery is a device that stores chemical energy and makes it available in an electrical form. ... Solar power describes a number of methods of harnessing energy from the light of the sun. ... A solar cell, made from a monocrystalline silicon wafer A solar cell (or a photovoltaic cell) is a device that converts photons from the sun (solar light) into electricity. ... Early 20th century Alternator made in Budapest, Hungary, in the power generating hall of a hydroelectric station. ... AC, half-wave and full wave rectified signals A rectifier is an electrical device, comprising one or more semiconductive devices (such as diodes) or vacuum tubes arranged for converting alternating current to direct current. ... This article is about the engineering discipline. ... A wall wart style variable DC power supply with its cover removed. ... A fuel cell is an electrochemical device similar to a battery, but differing from the latter in that it is designed for continuous replenishment of the reactants consumed; i. ...


Most telephones connect to a twisted pair of wires, and internally separate the AC component of the voltage between the two wires (the audio signal) from the DC component of the voltage between the two wires (used to power the phone). The telephone or phone is a telecommunications device which is used to transmit and receive sound (most commonly voice and speech) across distance. ... 25 Pair Color Code Chart 10BASE-T UTP Cable Twisted pair cabling is a common form of wiring in which two conductors are wound around each other for the purposes of cancelling out electromagnetic interference known as crosstalk. ...


Telephone exchange communication equipment, such as DSLAM, uses standard -48V DC power supply. The negative polarity is achieved by grounding the positive terminal of power supply system and the battery bank. This is done to prevent electrolysis depositions. A Verizon Central Office in Lakeland, Florida at night. ... A digital subscriber line access multiplexer, (DSLAM) is a multiplexer located in the telephone company exchange that provides consumers access to DSL services over twisted pair copper cabling. ... Ground symbols The term ground or earth usually means a common return path in electrical circuits. ... Four double-A (AA) rechargeable batteries In science and technology, a battery is a device that stores chemical energy and makes it available in an electrical form. ... It has been suggested that Electrolytic process be merged into this article or section. ...


See also

Electronics Portal

Image File history File links Nuvola_apps_ksim. ... It has been suggested that this article or section be merged with DC coefficient. ... City lights viewed in a motion blurred exposure. ...

External links


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