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Advantages of AC

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<onlyinclude>There are two types of electrical current, '''AC and DC'''. One flows back and forth alternating directions: [[alternating current]]. The other flows consistently in the same direction [[direct current]]. This page discusses the differences between the two, along with the advantages each carries along with it.</onlyinclude>

==Brief summary of AC and DC==
:''For more information on the specific currents, see their respective pages: [[AC]] and [[DC]]''

*'''Alternating current''' is [[electrical generation|produced]] within most types of [[power plant]]s by spinning [[generator]]s. The direction of [[current]] reverses, or alternates, 50-60 times per second depending on a country's standards.<ref name=hsw>How Stuff Works. (Accessed December 30, 2015). ''Direct Current Versus Alternating Current'' [Online], Available: http://science.howstuffworks.com/electricity8.htm</ref> Alternating current is the current that travels through [[electrical transmission#Power Lines|power lines]] and comes through the power [[outlet]]s found throughout a home or building. There are various reasons why AC was the current of choice to perform this task, which will be discussed below.

*'''Direct current''' is produced by power sources like [[battery|batteries]], [[fuel cell]]s, and [[solar panel]]s. Such power sources have two terminals that are positive and negative respectively, which creates a relatively constant voltage for electrons to flow through. Current always flows in the same direction between these two terminals.<ref name=hsw/>

<gallery mode=packed heights="280px" >
File:AC.gif|Figure 1. An animation from a PhET simulation of '''alternating current''' which has been slowed down considerably.<ref>http://phet.colorado.edu/sims/circuit-construction-kit/circuit-construction-kit-ac_en.jnlp</ref>
File:DC.gif|Figure 2. An animation from a PhET simulation of '''direct current''' which has been slowed down considerably.<ref>http://phet.colorado.edu/sims/circuit-construction-kit/circuit-construction-kit-ac_en.jnlp</ref>
</gallery>

==Advantages of each==

Alternating current uses of varying [[voltage]] and flow of [[electron]]s within a [[conductor]]. Direct current flows in one direction and with a <s>relatively</s> constant current (charge flowing by a point per unit time). The way each can be manipulated, however, is what is important, and provides clear advantages for certain applications among the two.

===Advantages of AC===

AC is the current of choice for power plants and the [[electrical grid]] as a whole. When a plug is connected to an [[electrical outlet]], alternating current comes out, providing power to countless devices like [[light bulb]]s and [[refrigerator]]s. AC is preferred for this application because:

<center>'''''There are cheap and reliable ways of increasing or decreasing the voltage using [[transformer]]s, which minimizes power loss in [[electrical transmission]].'''''</center>

[[Resistance]] reduces the energy transmitted in a wire. By increasing the voltage on the wires to very high voltages for long distance transmission, this loss can be reduced. The loss of power (<math>P_{lost}</math>) is given by the equation:<ref name=sec/>

<center><math>P_{lost}=I^2\times R</math></center>

where:

*<math>I</math> is the current in [[ampere]]s
*<math>R</math> is the resistance in [[ohm]]s

Increasing the voltages the grid transmits electricity reduces this lost power. As the voltage gets higher, the current decreases proportionally because the transmitted electrical power (energy per unit time) remains the same. For example, if the voltage is increased by a factor of 100, the current must decrease by a factor of 100 and the resulting power lost will be decreased by 100<sup>2</sup> = 10000. However there is a limit, being that at extremely high voltages (2000 kV) the electricity begins to discharge resulting in high losses.<ref name=sec>R. Paynter and B.J. Boydell, "Transmission Lines and Substations" in ''Introduction to Electricity'', 1st ed., Upper Saddle River, NJ: Pearson, 2011, ch.25, sec.3, pp.1102-1104</ref>

Efficient transmission saves power companies and consumers a lot of money, which helps reduce [[pollution]] since [[power plant]]s do not need to make up for lost electricity by using more [[fuel]].

Other advantages of AC include:<ref name=mark>Private communication with M. Pigman power engineer for Tacoma Power, Sept. 17th, 2015.</ref>
*Low maintenance costs of high speed AC motors.
*Easy to interrupt the current (ie. with a [[circuit breaker]]) due to the current going to zero naturally every 1/2 cycle. For example, a circuit breaker can interrupt about 1/20th as much DC as AC current.

===Advantages of DC===

A big advantage of direct current is that it is easier to change the speed of a DC [[electric motor]] than it is for an AC one. This is useful in many applications, such as [[electric vehicle|electric]] and [[hybrid car]]s.<ref name=mark/>

Direct current is used in essentially all consumer electronics, since [[transistor]]s (the building blocks of modern electronics) rely on it to operate. Devices that use DC current include [[cell phone]]s, laptops, TVs and much more.

Direct current may also be used to transmit electricity with even greater [[efficiency]] than alternating current ''over extremely large distances'' by use of [[HVDC transmission]] (high-voltage direct current). Along with higher efficiency, HVDC also allows for different AC systems (ie. 50 [[hertz|Hz]] and 60 Hz) to be connected.<ref>Spark Fun. (Accessed December 30, 2015). ''Alternating Current vs. Direct Current'' [Online], Available: https://learn.sparkfun.com/tutorials/alternating-current-ac-vs-direct-current-dc</ref>

== For Further Reading ==
For further information please see the related pages below:
*[[Electrical transmission]]
*[[Electrical grid]]
*[[Electrical generation]]
*[[Distribution grid]]
* Or explore a [[Special:Random| random page!]]

==References==
{{reflist}}

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