direct current

• 直流

関

DC

WordNet

1. straightforward in means or manner or behavior or language or action; "a direct question"; "a direct response"; "a direct approach"
2. having no intervening persons, agents, conditions; "in direct sunlight"; "in direct contact with the voters"; "direct exposure to the disease"; "a direct link"; "the direct cause of the accident"; "direct vote" (同)unmediated
3. in precisely the same words used by a writer or speaker; "a direct quotation"; "repeated their dialog verbatim" (同)verbatim
4. (of a current) flowing in one direction only; "direct current"
5. be in charge of
6. being an immediate result or consequence; "a direct result of the accident"
7. command with authority; "He directed the children to do their homework"
8. direct in spatial dimensions; proceeding without deviation or interruption; straight and short; "a direct route"; "a direct flight"; "a direct hit"
9. give directions to; point somebody into a certain direction; "I directed them towards the town hall"
10. guide the actors in (plays and films)
11. lacking compromising or mitigating elements; exact; "the direct opposite"
12. moving from west to east on the celestial sphere; or--for planets--around the sun in the same direction as the Earth
13. similar in nature or effect or relation to another quantity; "a term is in direct proportion to another term if it increases (or decreases) as the other increases (or decreases)"
14. occurring in or belonging to the present time; "current events"; "the current topic"; "current negotiations"; "current psychoanalytic theories"; "the ships current position"
15. a flow of electricity through a conductor; "the current was measured in amperes" (同)electric_current
16. a steady flow of a fluid (usually from natural causes); "the raft floated downstream on the current"; "he felt a stream of air"; "the hose ejected a stream of water" (同)stream
17. manageable by a supervising agent; "a directed program of study"
18. (often used in combination) having a specified direction; "a positively directed vector"; "goal-directed"
19. showing the way by conducting or leading; imposing direction on; "felt his mothers directing arm around him"; "the directional role of science on industrial progress" (同)directional, directive, guiding

PrepTutorEJDIC

1. 『まっすぐな』,一直線の(straight),直進する / (列車などが途中駅に寄らずに)直行 / 直系の / 『直接の』,じかの / 『率直な』,単刀直入の / 全くの,絶対の / 原典どおりの / 『まっすぐに』,直行で / 〈事〉‘を'『指揮する』,監督する / 《文》〈人〉‘に'『命令する』,指図する / 〈人〉‘に'(…への)『道を教える』《+『名』〈人〉+『to』+『名』》 / (…に)〈目・注意・努力など〉‘を'『向ける』《+『名』+『to』(『at, toward』)+『名』(do『ing』)》 / 〈音楽・演劇・映画など〉‘を'『指揮する』,演出する,監督する / (…に)〈手紙など〉‘を'あてる《+『名』+『to』+『名』》
2. 『通用している』,流通している,一般に行われている / 『今の』,『現在の』 / 〈C〉(水・空気などの)『流れ』,流動 / 〈C〉〈U〉電流 / 〈C〉(…の)『流れ』,『風潮』,動向《+『of』+『名』》
3. 恐ろしい,ものすごい;不吉な / 差し迫った(urgent);極端な

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/08/11 02:28:38」(JST)

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"LVDC" redirects here. For the computer, see Saturn Launch Vehicle Digital Computer.

Direct Current (red curve). The horizontal axis measures time; the vertical, current or voltage.

Direct current (DC) is the unidirectional flow of electric charge. Direct current is produced by sources such as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through semiconductors, insulators, or even through a vacuum as in electron or ion beams. The electric current flows in a constant direction, distinguishing it from alternating current (AC). A term formerly used for this type of current was galvanic current.

The abbreviations AC and DC are often used to mean simply alternating and direct, as when they modify current or voltage.

Direct current may be obtained from an alternating current supply by use of a current-switching arrangement called a rectifier, which contains electronic elements (usually) or electromechanical elements (historically) that allow current to flow only in one direction. Direct current may be made into alternating current with an inverter or a motor-generator set.

The first commercial electric power transmission (developed by Thomas Edison in the late nineteenth century) used direct current. Because of the significant advantages of alternating current over direct current in transforming and transmission, electric power distribution is nearly all alternating current today. In the mid-1950s, high-voltage direct current transmission was developed, and is now an option instead of long-distance high voltage alternating current systems. For long distance underseas cables (e.g. between countries, such as NorNed), this DC option is the only technically feasible option. For applications requiring direct current, such as third rail power systems, alternating current is distributed to a substation, which utilizes a rectifier to convert the power to direct current. See War of Currents.

Direct current is used to charge batteries, and in nearly all electronic systems, as the power supply. Very large quantities of direct-current power are used in production of aluminum and other electrochemical processes. Direct current is used for some railway propulsion, especially in urban areas. High-voltage direct current is used to transmit large amounts of power from remote generation sites or to interconnect alternating current power grids.

Electromagnetism
Electricity Magnetism
Electrostatics Electric charge Static electricity Electric field Conductor Insulator Triboelectricity Electrostatic discharge Induction Coulomb's law Gauss's law Electric flux / potential energy Electric dipole moment Polarization density
Magnetostatics Ampère's law Magnetic field Magnetization Magnetic flux Biot–Savart law Magnetic dipole moment Gauss's law for magnetism
Electrodynamics Lorentz force law Electromagnetic induction Faraday's law Lenz's law Displacement current Maxwell's equations Electromagnetic field Electromagnetic radiation Maxwell tensor Poynting vector Liénard–Wiechert potential Jefimenko's equations Eddy current London equations
Electrical network Electric current Electric potential Voltage Resistance Ohm's law Series circuit Parallel circuit Direct current Alternating current Charged current Neutral current Electromotive force Capacitance Inductance Impedance Resonant cavities Waveguides
Covariant formulation Electromagnetic tensor (stress–energy tensor) Four-current Electromagnetic four-potential
Scientists Ampère Coulomb Faraday Gauss Heaviside Henry Hertz Lorentz Maxwell Tesla Volta Weber Ørsted

Various definitions

Types of direct current

The term DC is used to refer to power systems that use only one polarity of voltage or current, and to refer to the constant, zero-frequency, or slowly varying local mean value of a voltage or current. 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 stationary voltage or current waveform can be decomposed into a sum of a DC component and a zero-mean time-varying component; the DC component is defined to be the expected value, or the average value of the voltage or current over all time.

Although DC stands for "direct current", DC often refers to "constant polarity". Under this definition, DC voltages can vary in time, as seen in 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.

Circuits

A direct current circuit is an electrical circuit that consists of any combination of constant voltage sources, constant current sources, and resistors. In this case, the circuit voltages and currents are independent of time. A particular circuit voltage or current does not depend on the past value of any circuit voltage or current. This implies that the system of equations that represent a DC circuit do not involve integrals or derivatives with respect to time.

If a capacitor or inductor is added to a DC circuit, the resulting circuit is not, strictly speaking, a DC circuit. However, most such circuits have a DC solution. This solution gives the circuit voltages and currents when the circuit is in DC steady state. Such a circuit is represented by a system of differential equations. The solution to these equations usually contain a time varying or transient part as well as constant or steady state part. It is this steady state part that is the DC solution. There are some circuits that do not have a DC solution. Two simple examples are a constant current source connected to a capacitor and a constant voltage source connected to an inductor.

In electronics, it is common to refer to a circuit that is powered by a DC voltage source such as a battery or the output of a DC power supply as a DC circuit even though what is meant is that the circuit is DC powered.

Applications

Direct-current installations usually have different types of sockets, connectors, 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).

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

The Unicode code point for the direct current symbol, found in the Miscellaneous Technical block, is U+2393 (⎓).

DC is commonly found in many extra-low voltage applications and some 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.

The vast majority of automotive applications use "12-volt" DC power; a few have a 6 V or a 42 V electrical system.

Light aircraft electrical systems are typically 12 V or 28 V.

Through the use of a DC-DC converter, high DC voltages such as 48 V to 72 V DC can be stepped down to 36 V, 24 V, 18 V, 12 V or 5 V to supply different loads. In a telecommunications system operating at 48 V DC, it is generally more efficient to step voltage down to 12 V to 24 V DC with a DC-DC converter and power equipment loads directly at their native DC input voltages versus operating a 48 V DC to 120 V AC inverter to provide power to equipment.

Many telephones connect to a twisted pair of wires, and use a bias tee to 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).

Telephone exchange communication equipment, such as DSLAM, uses standard −48 V 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.

See also

• Electric current
• High voltage direct current power transmission.
• Alternating current
• DC offset
• Neutral direct-current telegraph system

References

External links

• "AC/DC: What's the Difference?".
• "DC And AC Supplies" (PDF). ITACA. 

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English Journal

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• Direct electron transfer of Trametes hirsuta laccase adsorbed at unmodified nanoporous gold electrodes.

• Salaj-Kosla U, Pöller S, Schuhmann W, Shleev S, Magner E.SourceDepartment of Chemical and Environmental Sciences & Materials and Surface Science Institute, University of Limerick, Limerick, Ireland; Analytische Chemie - Elektroanalytik & Sensorik, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum, Germany.
• Bioelectrochemistry (Amsterdam, Netherlands).Bioelectrochemistry.2013 Jun;91:15-20. doi: 10.1016/j.bioelechem.2012.11.001. Epub 2012 Dec 8.
• The enzyme Trametes hirsuta laccase undergoes direct electron transfer at unmodified nanoporous gold electrodes, displaying a current density of 28μA/cm. The response indicates that ThLc was immobilised at the surface of the nanopores in a manner which promoted direct electron transfer, in contrast
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Japanese Journal

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• Biointerfacial Property of Plasma-Treated Single-Walled Carbon Nanotube Film Electrodes for Electrochemical Biosensors

• Kim Joon Hyub,Lee Jun-Yong,Jin Joon-Hyung,Park Eun Jin,Min Nam Ki
• Jpn J Appl Phys 52(1), 01AE02-01AE02-5, 2013-01-25
• … The plasma-functionalized (pf) SWCNT electrodes modified with Legionella pneumophila-specific probe DNA strands showed a much higher peak current and a smaller peak separation in differential pulse voltammetry and a lower charge transfer resistance, compared to the untreated samples. …
• NAID 150000106322

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Related Pictures

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★リンクテーブル★

リンク元	「DC」
関連記事	「direct」「current」

「DC」

　　[★]

• 樹状細胞 dendritic cell
• 直流 direct current

同

dyskeratosis congenita

「direct」

　　[★]

• adj.

• 直接の、直接的な、直接型の、ダイレクトな

• v.

• 指示する、向ける、指揮する、方向づける、指導する、配向する

関

coach、conduct、dictate、direction、directly、guidance、guide、immediate、indicate、indication、instruct、instruction、orient、orientation、point、straightforward、tutorial

　 　 　 　 　 　 　 　 　 　 　 　 　 　

「current」

　　[★]

• n.

• 電流、流れ

• adj.

• 現代の、現在の

関

as of、at present、contemporary、currently、flow、modern、now、present、present-day、presently、stream