Editing Direct current (section)

==Applications==
===Domestic and commercial buildings===
[[File:Direct current symbol.svg|right|200px|thumb|This symbol which can be represented with [[Unicode]] character {{U+|2393}} (⎓) is found on many electronic devices that either require or produce direct current.]]
DC is commonly found in many [[extra-low voltage]] applications and some [[low voltage|low-voltage]] applications, especially where these are powered by [[battery (electricity)|batteries]] or [[solar power]] systems (since both can produce only DC).

Most [[electronics|electronic]] circuits or devices require a DC [[power supply]].

Domestic DC installations usually have different types of [[Jack (connector)|sockets]], [[DC connector|connectors]], [[switch]]es, and [[Light fixture|fixtures]] from those suitable for alternating current. This is mostly due to the lower voltages used, resulting in higher currents to produce the same amount of [[Watt|power]].

It is usually important with a DC appliance to observe polarity, unless the device has a [[diode bridge]] to correct for this.

===Automotive===
Most automotive applications use DC. An [[automotive battery]] provides power for engine starting, lighting, the ignition system, the climate controls, and the infotainment system among others.  The [[alternator]] is an AC device which uses a [[rectifier]] to produce DC for battery charging.  Most highway passenger vehicles use nominally  12&nbsp;[[volt|V]] systems.  Many heavy trucks, farm equipment,  or earth moving equipment with [[Diesel engine]]s use 24 volt systems. In some older vehicles, 6&nbsp;V was used, such as in the original [[Volkswagen Beetle|classic Volkswagen Beetle]]. At one point a [[42&nbsp;V electrical system]] was considered for automobiles, but this found little use. To save weight and wire, often the metal frame of the vehicle is connected to one pole of the battery and used as the return conductor in a circuit.  Often the negative pole is the chassis "ground" connection, but positive ground may be used in some wheeled or marine vehicles.
In a [[battery electric vehicle]], there are usually two separate DC systems. The "low voltage" DC system typically operates at 12V, and serves the same purpose as in an internal combustion engine vehicle.<ref>{{Cite journal |last1=Pradhan |first1=S. K. |last2=Chakraborty |first2=B. |date=2022-07-01 |title=Battery management strategies: An essential review for battery state of health monitoring techniques |url=https://www.sciencedirect.com/science/article/pii/S2352152X22004509 |journal=Journal of Energy Storage |volume=51 |pages=104427 |doi=10.1016/j.est.2022.104427 |bibcode=2022JEnSt..5104427P |issn=2352-152X|url-access=subscription }}</ref> The "high voltage" system operates at 300-400V (depending on the vehicle), and provides the power for the [[traction motor|traction motors]].<ref>{{cite web |last1=Arcus |first1=Christopher |title=Tesla Model 3 & Chevy Bolt Battery Packs Examined |url=https://cleantechnica.com/2018/07/08/tesla-model-3-chevy-bolt-battery-packs-examined/ |website=CleanTechnica |date=8 July 2018 |access-date=6 June 2022}}</ref> Increasing the voltage for the traction motors reduces the current flowing through them, increasing efficiency.

===Telecommunication===
[[Telephone exchange]] communication equipment uses standard −48&nbsp;V DC power supply. The negative polarity is achieved by [[ground (electricity)|grounding]] the positive terminal of power supply system and the [[battery (electricity)|battery]] bank. This is done to prevent [[electrolysis]] depositions. Telephone installations have a battery system to ensure power is maintained for subscriber lines during power interruptions.

Other devices may be powered from the telecommunications DC system using a [[DC-DC converter]] to provide any convenient voltage.

Many [[telephone]]s 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).

===High-voltage power transmission===
{{main|High-voltage direct current}}
High-voltage direct current (HVDC) [[electric power transmission]] systems use DC for the bulk transmission of electrical power, in contrast with the more common alternating current systems. For long-distance transmission, HVDC systems may be less expensive and suffer lower electrical losses.

===Other===
Applications using [[fuel cells]] (mixing hydrogen and oxygen together with a catalyst to produce electricity and water as byproducts) also produce only DC.

Light aircraft electrical systems are typically 12&nbsp;V or 24&nbsp;V DC similar to automobiles.