Reactance In the analysis of an alternating-current electrical circuit (for example a RLC series circuit), reactance is the imaginary part of impedance, and is caused by the presence of inductors or capacitors in the circuit. Reactance is denoted by the symbol X and is measured in ohms. If X > 0, the reactance is said to be inductive If X = 0, then the circuit is purely resistive, i.e. it has no reactance. If X < 0, it is said to be capacitive. The reciprocal of reactance is susceptance. The relationship between impedance, resistance, and reactance is given by the equation: $Z\; =\; R\; +\; j\; X\; \backslash ,$ Often it is enough to know the magnitude of the impedance: $\backslash left\; |\; Z\; \backslash right\; |\; =\; \backslash sqrt\; \backslash ,$ where Z is impedance, measured in ohms R is resistance, measured in ohms X is reactance, measured in ohms Inductive reactance (symbol XL) is caused by the fact that a current is accompanied by a magnetic field; therefore a varying current is accompanied by a varying magnetic field; the latter gives an electromotive force that resists the changes in current. The more the current changes, the more an inductor resists it: the reactance is proportional with the frequency (hence zero for DC). There is also a phase difference between the current and the applied voltage. Inductive reactance has the formula $X\_L=2\backslash pi\; fL\; \backslash ,\backslash !$ where XL is the inductive reactance, measured in ohms f is the frequency, measured in hertz L is the inductance, measured in henry Capacitive reactance (symbol XC) reflects the fact that electrons can not pass, yet effectively alternating current (AC) can: the higher the frequency the better. There is also a phase difference between the alternating current flowing through a capacitor and the potential difference across the capacitor's electrodes. Capacitive reactance has the formula $X\_C=\; \backslash frac\; \backslash ,$ where XC is the capacitive reactance measured in ohms f is the frequency, measured in hertz C is the capacitance, measured in farad SI electricity units External links Resistance, Reactance, and Impedance FAVORITE ARTICLES: History of the World    History of the United States    History of Europe    Ancient History    History    Military History    World War I    Bombing of Dresden    California    US Constitution    Frank Sinatra    Boston    Marbury v. Madison This article is licensed under the GNU Free Documentation License at http://www.gnu.org/copyleft/fdl.html You may copy and modify it as long as the entire work (including additions) remains under this license. You must provide a link to http://www.gnu.org/copyleft/fdl.html To view or edit this article at Wikipedia go to http://www.wikipedia.org/wiki/Reactance">follow this link. All other content is copyright © 2000-2005 by WorldHistory.com. All rights reserved.

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