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{{other uses|Reactance (disambiguation)}}
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In electrical and electronic systems, '''reactance''' is the opposition of a circuit element to a change of [[electric current]] or [[voltage]], due to that element's [[inductance]] or [[capacitance]]. A built-up [[electric field]] resists the change of voltage on the element, while a [[magnetic field]] resists the change of current. The notion of reactance is similar to [[electrical resistance]], but they differ in several respects.
 
An ideal [[resistor]] has zero reactance, while ideal [[inductor]]s and [[capacitor]]s consist entirely of reactance. The magnitude of the reactance of an inductor is proportional to frequency, while the magnitude of the reactance of a capacitor is inversely proportional to frequency.
 
== Analysis ==
 
In [[phasor]] analysis, reactance is used to compute amplitude and phase changes of [[Sine wave|sinusoidal]] [[alternating current]] going through the circuit element. It is denoted by the symbol <math>\scriptstyle{X}</math>.
 
Both reactance <math>\scriptstyle{X}</math> and [[Electrical resistance|resistance]] <math>\scriptstyle{R}</math> are components of [[Electrical impedance|impedance]] <math>\scriptstyle{Z}</math>.
 
:<math>Z = R + jX\,</math>
 
:where
*<math>\scriptstyle{Z}</math> is the [[Electrical impedance|impedance]], measured in ohms.
*<math>\scriptstyle{R}</math> is the [[Electrical resistance|resistance]], measured in ohms.
*<math>\scriptstyle{X}</math> is the reactance, measured in ohms.
*<math>\scriptstyle j \;=\; \sqrt{-1}</math>
 
Both capacitive reactance <math>\scriptstyle{X_C}</math> and inductive reactance <math>\scriptstyle{X_L}</math> contribute to the total reactance <math>\scriptstyle{X}</math>.
 
:<math>{X = X_L - X_C = \omega L -\frac {1} {\omega C}}</math>
 
:where
* <math>\scriptstyle{X_C}</math> is the [[Capacitance|capacitive]] reactance, measured in ohms
* <math>\scriptstyle{X_L}</math> is the [[Inductance|inductive]] reactance, measured in ohms
 
Although <math>\scriptstyle{X_L}</math> and <math>\scriptstyle{X_C}</math> are both positive by convention, the capacitive reactance <math>\scriptstyle{X_C}</math> makes a negative contribution to total reactance.
 
Hence,
 
* If <math>\scriptstyle X \;>\; 0</math>, the reactance is said to be [[Inductance|inductive]].
* If <math>\scriptstyle X \;=\; 0</math>, then the impedance is purely [[Electrical resistance|resistive]].
* If <math>\scriptstyle X \;<\; 0</math>, the reactance is said to be [[Capacitance|capacitive]]
 
== Capacitive reactance ==
{{main|Capacitance}}
 
'''Capacitive reactance''' is an opposition to the change of voltage across an element. Capacitive reactance <math>\scriptstyle{X_C}</math> is [[inversely proportional]] to the signal [[frequency]] <math>\scriptstyle{f}</math> (or [[angular frequency]] ω) and the [[capacitance]] <math>\scriptstyle{C}</math>.<ref>Irwin, D. (2002). ''Basic Engineering Circuit Analysis'', page 274. New York: John Wiley & Sons, Inc.</ref>
 
:<math>X_C = \frac {1} {\omega C} = \frac {1} {2\pi f C}</math> <ref>http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html</ref>
 
A capacitor consists of two [[Electrical conduction|conductor]]s separated by an [[Electrical insulation|insulator]], also known as a [[dielectric]].
 
At low frequencies a capacitor is [[open circuit]], as no [[Electric current|current]] flows in the dielectric.  A [[Direct current|DC]] voltage applied across a capacitor causes positive [[Electrical charge|charge]] to accumulate on one side and negative [[Electrical charge|charge]] to accumulate on the other side; the [[electric field]] due to the accumulated charge is the source of the opposition to the current. When the [[potential]] associated with the charge exactly balances the applied voltage, the current goes to zero.
 
Driven by an AC supply, a capacitor will only accumulate a limited amount of charge before the potential difference changes polarity and the charge dissipates.  The higher the frequency, the less charge will accumulate and the smaller the opposition to the current.
 
== Inductive reactance ==
{{main|Inductance}}
 
'''Inductive reactance''' is an opposition to the change of current through an element. Inductive reactance <math>\scriptstyle{X_L}</math> is [[Proportionality (mathematics)|proportional]] to the sinusoidal signal [[frequency]] <math>\scriptstyle{f}</math> and the [[inductance]] <math>\scriptstyle{L}</math>.
:<math>X_L = \omega L = 2\pi f L</math>
 
The average current flowing in an [[inductance]] <math>\scriptstyle{L}</math> in series with a sinusoidal AC voltage source of RMS [[amplitude]] <math>\scriptstyle{A}</math> and frequency <math>\scriptstyle{f}</math> is equal to:
:<math>I_L = {A \over \omega L} = {A \over 2\pi f L}.</math>
 
The average current flowing in an [[inductance]] <math>\scriptstyle{L}</math> in series with a square wave AC voltage source of RMS [[amplitude]] <math>\scriptstyle{A}</math> and frequency <math>\scriptstyle{f}</math> is equal to:
:<math>I_L = {A \pi^2 \over 8 \omega L} = {A\pi \over 16 f L}</math> making it appear as if the inductive reactance to a square wave was <math>X_L = {16 \over \pi} f L</math>
 
An inductor consists of a [[Coil#Electromagnetic coils|coiled conductor]].  [[Faraday's law of induction|Faraday's law]] of electromagnetic induction gives the counter-[[Electromotive force|emf]] <math>\scriptstyle{\mathcal{E}}</math> (voltage opposing current) due to a rate-of-change of [[magnetic flux density]] <math>\scriptstyle{B}</math> through a current loop.
 
:<math>\mathcal{E} = -{{d\Phi_B} \over dt}</math>
 
For an inductor consisting of a coil with <math>\scriptstyle N</math> loops this gives.
 
:<math>\mathcal{E} = -N{d\Phi_B \over dt}</math>
 
The counter-emf is the source of the opposition to current flow.  A constant [[direct current]] has a zero rate-of-change, and sees an inductor as a [[short-circuit]] (it is typically made from a material with a low [[resistivity]]). An [[alternating current]] has a time-averaged rate-of-change  that is proportional to frequency, this causes the increase in inductive reactance with frequency.
 
== Phase relationship ==
 
The phase of the voltage across a purely reactive device (a capacitor with an infinite resistance or an inductor with a resistance of zero) ''lags'' the current by <math>\scriptstyle{\pi/2}</math> radians for a capacitive reactance and ''leads'' the current by <math>\scriptstyle{\pi/2}</math> radians for an inductive reactance.  Note that without knowledge of both the resistance and reactance the relationship between voltage and current cannot be determined.
 
The origin of the different signs for capacitive and inductive reactance is the phase factor in the impedance.
 
:<math>\begin{align}
  \tilde{Z}_C &= {1 \over \omega C}e^{j(-{\pi \over 2})} = -j\left({ \frac{1}{\omega C}}\right) = -jX_C \\
  \tilde{Z}_L &= \omega Le^{j{\pi \over 2}} = j\omega L = jX_L\quad
\end{align}</math>
 
For a reactive component the sinusoidal voltage across the component is in quadrature (a <math>\scriptstyle{\pi/2}</math> phase difference) with the sinusoidal current through the component. The component alternately absorbs energy from the circuit and then returns energy to the circuit, thus a pure reactance does not dissipate power.
 
==See also==
*[[Electrical measurements]]
* [[Susceptance]]
* [[Magnetic reactance]]
 
== References ==
# Pohl R. W. ''Elektrizitätslehre.'' – Berlin-Göttingen-Heidelberg: Springer-Verlag, 1960.
# Popov V. P.  ''The Principles of Theory of Circuits.'' – M.: Higher School, 1985, 496 p. (In Russian).
# [[Karl Küpfmüller|Küpfmüller K.]] ''Einführung in die theoretische Elektrotechnik,'' Springer-Verlag, 1959.
# {{cite book | author = Young, Hugh D. | coauthors = Roger A. Freedman and A. Lewis Ford | title = Sears and Zemansky's University Physics | origyear = 1949 | year = 2004 | edition = 11 ed | accessdate = 2006-09-30 | publisher = [[Addison Wesley]] | location = [[San Francisco]] | isbn= 0-8053-9179-7}}
<references/>
 
== External links ==
* [http://www.magnet.fsu.edu/education/tutorials/java/inductivereactance/index.html Interactive Java Tutorial on Inductive Reactance] National High Magnetic Field Laboratory
 
[[Category:Electronics]]
[[Category:Physical quantities]]
 
[[he:עכבה חשמלית#היגב]]

Revision as of 22:28, 25 February 2014

If your computer is running slow, you have probably gone by the different stages of rage and frustration. Having such a good tool like a computer can appear like a curse plus a blessing simultaneously whenever this happens. It is good when it's running quickly and smooth, however then when it begins acting strange plus slows method down, frustration sets inside. How could something because beautiful as a computer make a individual thus mad?

Google Chrome crashes on Windows 7 by the corrupted cache contents plus issues with the stored browsing information. Delete the browsing data and clear the contents of the cache to solve this issue.

If you compare registry products we need a quickly acting registry cleaning. It's no good spending hours and a PC waiting for a registry cleaning to complete its task. We wish your cleaner to complete its task inside minutes.

The 1328 error is a usual issue caused by the program being unable to properly procedure numerous changes for the program or Microsoft Office. If you have this error, it mostly signifies that a computer is either unable to read the actual update file or a computer has difficulties with all the settings it's utilizing to run. To fix this problem, you first should change / fix any difficulties which a computer has with its update files, plus then repair any of the issues which your system might have.

After which, I furthermore bought the Regtool fix it utilities Software, and it further protected my laptop having program crashes. All my registry problems are fixed, plus I can work peacefully.

Another key element when we compare registry products is having a center to manage the start-up jobs. This merely signifies to choose what programs you want to commence whenever you start your PC. If you have unwanted programs starting when we boot up a PC this may lead to a slow running computer.

Maybe you're asking why these windows XP error messages appear. Well, for you to be able to understand the fix, you must initially know where those errors come from. There is this software called registry. A registry is software which stores everything on a PC from a regular configuration, setting, information, and logs of activities from installing to UN-installing, saving to deleting, plus a lot more alterations we do inside a program pass from it and gets 'tagged' and saved as a simple file for healing reasons. Imagine it because a big recorder, a registrar, of all your records inside a PC.

Fortunately, there's a easy technique to fix most your computer errors. You simply want to be capable to fix corrupt registry files on a computer. And to do that, you could really use a tool recognised as a registry cleaner. These simple pieces of software really scan from a PC and fix every corrupt file that would result a issue to Windows. This enables your computer to employ all the files it wants, that not merely speeds it up - but also stops all the errors on a system too.