Reactance Vs. Susceptance And Impedance Vs. Admittance - Difference?

Reactance Vs. Susceptance And Impedance Vs. Admittance - Difference?

Hi can any one tell the difference between reactance and susceptance ?
and Impedance and Admittance? It can be a silly question😖 but i didn’t get them and its difference!😭

Understanding Electrical Properties: Reactance Vs. Susceptance And Impedance Vs. Admittance - Key Differences Explored

Electricity is a broad and complex field of study, primarily due to the various properties it exhibits. Two of the fundamental concepts in electrical engineering are reactance and susceptance and impedance and admittance. Understanding these terms and how they differ can provide a deeper understanding of how electrical circuits function.

Reactance and Susceptance

Reactance (X) and susceptance (B) are essential components in alternating current (AC) circuit analysis. These concepts are linked to the impedance, capacitance, and inductance of an AC circuit.


Reactance is a measure of how a circuit reacts to an AC input. It is the dynamic resistance that an inductor or a capacitor provides in an AC circuit.

Reactance can be of two types, inductive reactance (X_L) and capacitive reactance (X_C).

Inductive reactance, proportional to the frequency of the alternating current and the inductance of the circuit, increases with increasing frequency.

Conversely, capacitive reactance is inversely proportional to the frequency and the capacitance, hence decreases with increasing frequency.

The unit of reactance is ohms (Ω), just like resistance, but reactance is a complex quantity.

Its value can be positive or negative, indicating that it can either absorb energy from the circuit (positive, as in inductors) or release energy into it (negative, as in capacitors).


On the other hand, susceptance is the reciprocal of reactance, which means it measures the ease with which alternating current can pass through a reactive component.

Susceptance is represented by the letter B and measured in Siemens (S). Similar to reactance, susceptance can also be capacitive (B_C) or inductive (B_L), depending on whether the element is a capacitor or inductor.

Capacitive susceptance is positive and inductive susceptance is negative, highlighting the energy-exchange properties of capacitors and inductors in a circuit.

Impedance and Admittance

Impedance (Z) and admittance (Y) are two more fundamental electrical properties often encountered in AC circuit analysis.

They relate to the overall opposition or facilitation of electric current in a circuit, considering both resistive and reactive elements.


Impedance is a complex measure of how much a circuit opposes the flow of electric current, combining both resistance (R) and reactance (X).

This opposition to current in an AC circuit is due to both the resistive elements (resistors) and the reactive elements (capacitors and inductors).

Impedance is measured in ohms (Ω) and is represented as a complex number, with the real part being the resistance and the imaginary part being the reactance.


Admittance is the inverse of impedance, meaning it represents how easily an AC circuit allows the flow of current.

It comprises conductance (G), the reciprocal of resistance, and susceptance (B), the reciprocal of reactance.

Admittance is measured in Siemens (S) and, like impedance, is also a complex number.

The real part of admittance is the conductance, while the imaginary part is the susceptance.

Key Differences

1. Reciprocal relationship: Reactance is inversely related to susceptance, and impedance is inversely related to admittance. This difference means that as reactance increases, susceptance decreases, and as impedance increases, admittance decreases.

2. Energy exchange: Reactance and impedance can absorb or supply energy to the circuit, depending on the reactive components involved, while susceptance and admittance merely describe the ability of a circuit to allow current to flow.

3. Measurement units: Reactance and impedance are measured in ohms (Ω), while susceptance and admittance are measured in Siemens (S).

Understanding these four electrical properties and their differences is crucial in the analysis of AC circuits.

Reactance and impedance consider both energy absorption and supply, making them essential for studying the dynamic behaviour of circuits.

In contrast, susceptance and admittance offer a perspective on how readily a circuit allows current to flow, providing insight into the circuit's performance in real-life applications.

Let drive into the practical applications of reactance, susceptance, impedance, and admittance.

Practical Applications of Reactance, Susceptance, Impedance, and Admittance


Reactance finds wide-ranging applications in the realm of AC electronics and power systems. For instance:

  • Filter Design: The concepts of inductive and capacitive reactance are essential in the design of electrical filters, which allow certain frequencies to pass while blocking others. This is crucial in many electronics devices, including radios and televisions.

  • Tuning Circuits: Reactance is used in tuning circuits such as those in a radio receiver. By adjusting the reactance, you can select which frequency you want to listen to.

  • Power Factor Correction: Reactance is critical in power systems for power factor correction, a technique to reduce the angle difference between current and voltage in AC systems, leading to more efficient power use.


Susceptance, being the inverse of reactance, also plays a significant role in AC systems:

  • Transmission Line Analysis: Susceptance is used in the modeling and analysis of transmission lines, helping to predict the performance of long-distance power transmission.

  • Electrical Networks: Susceptance simplifies the analysis of complex electrical networks, particularly those with parallel and series circuits, enhancing the understanding of their behavior under varying frequencies.


Impedance, being a comprehensive measure of opposition to current, finds broad application:

  • Speaker Systems: In audio systems, matching the impedance of speakers to the amplifier is crucial to ensure optimal sound reproduction and to avoid damage to the system.

  • Transmission Lines: Impedance matching in transmission lines prevents signal reflection and ensures the maximum power is transferred.

  • Electrical Circuit Design: In designing circuits for various electronic devices, understanding impedance helps in deciding the appropriate components to use for achieving desired performance.


Admittance, like susceptance, simplifies many aspects of AC circuit analysis and finds various applications:

  • Electrical Network Analysis: Admittance simplifies calculations in complex networks, making it easier to predict how the network will behave under different conditions.

  • Sensors: Admittance is used in certain types of sensors, such as capacitive proximity sensors, where changes in admittance can indicate changes in the environment.

In conclusion, reactance, susceptance, impedance, and admittance are vital elements in electrical engineering and electronics.

They aid in designing, analyzing, and optimizing electronic and power systems to function efficiently and effectively.

By understanding these properties, engineers can ensure that electrical systems are safe, efficient, and perform to their maximum potential.

I hope this makes the differences clear.


  • hsirah5
    Reactance is the opposition caused to alternating emf/current. It may sound similar to resistance but reactance is observed only in case of alternating current, whereas resistance is the opposition to current both in the case of AC & DC.

    In a capacitor, the charges that accumulate on the capacitance plate creates an electric field causes the capacitive reactance and opposes the electron flow. In inductors, the magnetic field that is created due to flow of current through an induction coil contributes to inductive reactance.

    The total opposition to the flow of current/emf is called Impedance.

    Admittance is a complementary measure of impedance and shows how much a circuit allows (or admits) current flow.
    Susceptance is a measure how much a circuit is capable of conducting a varying current.

    Assuming that you have knowledge on real and imaginary parts of powers, we can mathematically represent impedance as follows

    Impedance = Resistance + j . Reactance (where j^2 = -1)
    Reactance is the imaginary part of impedance.

    Admittance = Conductance + j . Susceptance
    Susceptance is the imaginary part of admittance.

    Admittance = 1 / Impedance

    Hope this would give you a good idea...😎

    Hi can any one tell the difference between reactance and susceptance ?😎
    and Impedance and Admittance?
    It can be a silly question😖 but i didnt get them and its difference!😭

You are reading an archived discussion.

Related Posts

I heard many times that if you have some problem with your Nokia phone,so it is also suggested that to do Flash with mobile. I just want to know that...
My name is Tethra and am B. Eng holder in Electronic and systems Engineering. I would like to learn more about Systems Engineering and be a CEng one day.
I would like to know about the latest short term courses that i can pursue after my graduation and about the colleges that offer them...preferably in India...
The ambitious project called 'Skylon SpacePlane' is a hybrid plane using a Sabre engine that allows edge of space travel. No where on Earth is more than 4 hours away...
If you are an Ubuntu fan and looking forward to installing Ubuntu 12.04, you would like to go through this video - If you don't want to bother seeing that...