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Encyclopedia > Reactance
It has been suggested that Electric reactance be merged into this article or section. (Discuss)
This article is about electronics. For a discussion of "reactive" or "reactance" in chemistry, see reactivity.
For a discussion of the psychological concept of reactance, see reactance (psychology).

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. Image File history File links Please see the file description page for further information. ... It has been suggested that this article or section be merged into AC power. ... The field of electronics is the study and use of systems that operate by controlling the flow of electrons (or other charge carriers) in devices such as thermionic valves and semiconductors. ... Chemistry (derived from alchemy) is the science of matter at or near the atomic scale. ... Reactivity refers to the rate at which a chemical substance tends to undergo a chemical reaction in time. ... Reactance is an action in direct contradiction to rules and/or regulations that threaten or eliminate specific behavioral freedoms; it can occur when someone is heavily pressured to accept a certain view or attitude. ... City lights viewed in a motion blurred exposure. ... Lightning strikes during a night-time thunderstorm. ... An electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, and switches. ... An RLC circuit is a kind of electrical circuit composed of a resistor (R), an inductor (L), and a capacitor (C). ... In electrical engineering, Impedance is a measure of opposition to a sinusoidal electric current. ... An inductor is a passive electrical device employed in electrical circuits for its property of inductance. ... A capacitor is a device that stores energy in the electric field created between a pair of conductors on which electric charges of equal magnitude, but opposite sign, have been placed. ... The ohm (symbol: Ω) is the SI unit of electric resistance. ...

  • 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 relationship between impedance, resistance, and reactance is given by the equation: Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ...

Z = R + j X ,

where

Z is impedance, measured in ohms
R is resistance, measured in ohms
X is reactance, measured in ohms
j is the imaginary unit


Often it is enough to know the magnitude of the impedance: The ohm (symbol: Ω) is the SI unit of electric resistance. ...

left | Z right | = sqrt {R^2 + X^2} ,

For a purely inductive or capacitive element, the magnitude of the impedance simplifies to just the reactance.


The reactance is given by

X = X_L - X_C ,

where XL and XC are the inductive and capacitive reactances, respectively.


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 to the frequency (hence zero for DC). There is also a phase difference between the current and the applied voltage. Current flowing through a wire produces a magnetic field (B, labeled M here) around the wire. ... Electromotive force (emf),[hammid the smelly fucking arab that cant hold his farts] often denoted by , is a measure of the strength of a source of electrical energy. ... Direct current (DC or continuous current) is the continuous flow of electricity through a conductor such as a wire from high to low potential. ... Waves with the same phase Waves with different phases The phase of a wave relates the position of a feature, typically a peak or a trough of the waveform, to that same feature in another part of the waveform (or, which amounts to the same, on a second waveform). ...


Inductive reactance has the formula

X_L = omega L = 2pi f L ,!

where

XL is the inductive reactance, measured in ohms
ω is the angular frequency, measured in radians per second
f is the frequency, measured in hertz
L is the inductance, measured in henries

Capacitive reactance (symbol XC) reflects the fact that electrons cannot pass through a capacitor, 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. Angular frequency is a measure of how fast an object is rotating In physics (specifically mechanics and electrical engineering), angular frequency ω (also called angular speed) is a scalar measure of rotation rate. ... Angular frequency is a measure of how fast an object is rotating In physics (specifically mechanics and electrical engineering), angular frequency ω (also called angular speed) is a scalar measure of rotation rate. ... Sine waves of various frequencies; the lower waves have higher frequencies than those above. ... The hertz (symbol: Hz) is the SI unit of frequency. ... Inductance (or electric inductance) is a measure of the amount of magnetic flux produced for a given electric current. ... An inductor. ... A capacitor is a device that stores energy in the electric field created between a pair of conductors on which electric charges of equal magnitude, but opposite sign, have been placed. ... Potential difference is a quantity in physics related to the amount of energy that would be required to move an object from one place to another against various types of force. ...


Capacitive reactance has the formula

X_C = frac {1} {omega C} = frac {1} {2pi f C} ,

where

XC is the capacitive reactance measured in ohms
ω is the angular frequency, measured in radians per second
f is the frequency, measured in hertz
C is the capacitance, measured in farads

Angular frequency is a measure of how fast an object is rotating In physics (specifically mechanics and electrical engineering), angular frequency ω (also called angular speed) is a scalar measure of rotation rate. ... Sine waves of various frequencies; the lower waves have higher frequencies than those above. ... // Definition Capacitance is a measure of the amount of electric charge stored (or separated) for a given electric potential. ... The farad (symbol: F) is the SI unit of capacitance. ...

See also

SI electromagnetism units ...


Xc = Capacitive reactance: Opposition to Current.


XL = Inductive reactance : Opposition to Voltage.


External links

  • Resistance, Reactance, and Impedance

  Results from FactBites:
 
What is reactance? - a definition from Whatis.com (0 words)
Resistance and reactance combine to form impedance, which is defined in terms of two-dimensional quantities known as complex number.
As the inductance of a component increases, its inductive reactance becomes larger in imaginary terms, assuming the frequency is held constant.
As the capacitance of a component increases, its capacitive reactance becomes smaller negatively (closer to zero) in imaginary terms, assuming the frequency is held constant.
Reactance (362 words)
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 produces a phase shift between the electric current and voltage in the circuit.
Reactance is denoted by the symbol X and is measured in ohms.
  More results at FactBites »

 
 

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