Definition and Concept of Reactance
– Reactance is the opposition presented to alternating current by inductance and capacitance.
– It is one of two elements of impedance, along with resistance.
– Reactance does not dissipate electrical energy as heat, but stores energy and returns it to the circuit.
– Greater reactance results in smaller current for the same applied voltage.
– Reactance is measured in ohms and can be inductive or capacitive.
– A circuit with only reactance can be treated the same as a circuit with only resistances.
– Complex numbers are often needed to combine reactance and resistance.
– Reactance changes the phase of current relative to voltage.
– Reactances can be negative and cancel each other out.
Capacitive Reactance
– Capacitive reactance is the opposition to the change of voltage across a capacitor.
– It is inversely proportional to the signal frequency and capacitance.
– Capacitive reactance can be defined as a negative or positive number.
– At low frequencies, capacitive reactance is high, behaving like an open circuit.
– As frequency increases, capacitive reactance decreases, behaving like a short circuit.
Inductive Reactance
– Inductive reactance is a property exhibited by an inductor.
– It opposes the change of current through an element.
– An ideal inductor causes the current to lag the voltage by a quarter cycle.
– Inductive reactance can limit the power capacity of an AC transmission line.
– Power providers use capacitors to minimize losses caused by inductive reactance.
Applications and History
– Reactance was first suggested by French engineer M. Hospitalier in 1893.
– It was officially adopted by the American Institute of Electrical Engineers in 1894.
– Capacitive reactance is used in capacitors to store and release electrical energy.
– Inductive reactance is utilized in inductors for applications like transformers and motors.
– Reactance plays a crucial role in the design and analysis of electrical circuits.
Relationship with Frequency, Phase Relationship, and Power Dissipation
– Inductive reactance increases with frequency.
– Capacitive reactance decreases with frequency.
– Reactance is directly proportional to frequency in both inductive and capacitive components.
– The total reactance in a circuit is the sum of the individual reactances.
– The impedance of a circuit is the total opposition to current flow and is a combination of resistance and reactance.
– The phase relationship between voltage and current in a purely reactive device depends on the type of reactance.
– For a capacitive reactance, the voltage lags the current by π/2 radians.
– For an inductive reactance, the voltage leads the current by π/2 radians.
– A pure reactance does not dissipate power.
– The sinusoidal voltage across a reactive component is in quadrature with the sinusoidal current.
– The component alternately absorbs and returns energy to the circuit.
– Power is only dissipated in resistive components.
– Reactance is responsible for storing and releasing energy in the circuit. Source: https://en.wikipedia.org/wiki/Electrical_reactance
In electrical circuits, reactance is the opposition presented to alternating current by inductance and capacitance. Along with resistance, it is one of two elements of impedance; however, while both elements involve transfer of electrical energy, no dissipation of electrical energy as heat occurs in reactance; instead, the reactance stores energy until a quarter-cycle later when the energy is returned to the circuit. Greater reactance gives smaller current for the same applied voltage.
Reactance is used to compute amplitude and phase changes of sinusoidal alternating current going through a circuit element. Like resistance, reactance is measured in ohms, with positive values indicating inductive reactance and negative indicating capacitive reactance. It is denoted by the symbol . An ideal resistor has zero reactance, whereas ideal inductors and capacitors have zero resistance. As frequency increases, inductive reactance increases and capacitive reactance decreases.
