Electrical Reactance

Electrical Reactance

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.

Capacitance and inductance are inherent properties of an element, just like resistance. Reactive effects are not exhibited under constant direct current, but only when the conditions in the circuit change. Thus, the reactance differs with the rate of change, and is a constant only for circuits under alternating current of constant frequency. In vector analysis of electric circuits, resistance is the real part of complex impedance, while reactance is the imaginary part. Both share the same SI unit, the ohm.

An ideal resistor has zero reactance, while ideal inductors and capacitors consist entirely of reactance.

Read more about Electrical Reactance:  Analysis, Capacitive Reactance, Inductive Reactance, Phase Relationship

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Electrical Reactance - Phase Relationship
... a resistance of zero) lags the current by radians for a capacitive reactance and leads the current by 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 For a reactive component the sinusoidal voltage across the component is in quadrature (a ...

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