Know About Electrical Impedance And Its Application

The term impedance is commonly used if someone connects a loudspeaker (amplifier) to an audio system; it is normally a number of Ohms, regularly printed next to many inputs or to an output socket. Though the property of impedance is less understood, the word impedance is used in many engineering disciplines to refer to as an opponent to work done. Anyway, this article refers particularly to electrical impedance, which describes a combined effect of resistance (R), inductive reactance (XL) and capacitive reactance (XC) in an AC circuit, whether it is occurring in a single component, or in an entire circuit.

What is Electrical Impedance?

Electrical impedance (also known as “impedance” in short) is an addition of the definition of resistance to an alternating current(AC). This means that impedance includes both resistance (opposition of the electric current that causes heat) and reactance (a measure of such an oppositional current alternates) – in detail, the opposition adjacent to the electric currents. In the direct current (DC), electrical impedance is the same as resistance, except that it does not hold true in AC circuits.

Electrical Impedance
Electrical Impedance

Impedance can also be dissimilar from resistance when a DC circuit changes flow in one way or another- similar to the opening and closing of an electrical switch, as is observed in the computers when they open and close switches to represent ones and zeros (binary language). The opposite of impedance is admittance, which is the measure of the allowance of current. The figure to the left is a complex impedance plane, in which impedance is represented by a Z, resistance is depicted as R, and the reactance is depicted with X.

Electrical Impedance Tomography (EIT)

The fundamental principle of electrical impedance tomography (EIT) is akin to electrical resistance tomography (ERT) such that several measurements at the periphery of a process vessel or tube are taken and combined to give information on the electrical properties of the process volume.

Electrical Impedance Tomography
Electrical Impedance Tomography

Electrical Impedance Tomography (EIT) is a non-invasive medical imaging method in which a figure of the conductivity or permittivity of a part of the body is incidental from the surface electrode measurements. Electrical conductivity depends on the free ion content and differs significantly between different biological tissues (absolute EIT) or dissimilar practical states of one and other similar tissues or organs (relative or functional EIT). The majority of EIT systems apply little irregular currents at a single frequency; however, some EIT systems use various frequencies to better discriminate between usual and suspected abnormal tissue within the same organ (multifrequency-EIT or electrical impedance spectroscopy).

Complex Impedance

A resistor with a value of R has an impedance of R ohms, a real number. An ideal inductor has a complex impedance of



Where ‘f’ is the frequency in Hertz and L is the inductance in Henries. It is imaginary because an ideal inductor can simply store and release electrical energy. It can’t dissipate it as heat like a resistor. Similarly, an ideal capacitor has a complex impedance of

Z = -j/2πfc

Where ‘C’ is the capacitance in farads.

Use of Complex Impedance

The behavior of the impedance of an AC circuit with various components quickly becomes unmanageable if sines and cosines are used to present the voltages and current. A mathematical build that eases the complexity use of complex exponential functions. The necessary parts of the strategy are as follows

Math relationship underlaying the technique

ejωt = cosωt + sinωt

The real part of a complex exponential function can be used to represent an AC voltage or current.

V = Vm COSωt

I =Im COS (ωt-φ)

The impedance can then be expressed as a complex exponential

Z = Vm/ Im e-jØ = R+jX

The impedance of the individual circuit elements can then be expressed as pure real or imaginary numbers.

R –j/ωc jωL

Complex Impedance for RL and RC

Using complex impedance is a significant technique for handling multi-component AC circuits. If a complex plane is used with resistance along the real axis, then the reactance of a capacitor and inductor are treated as imaginary numbers. For series combinations of the components such as RL and RC combinations, the component values are added as if they were components of a vector. Shown now is the Cartesian form of the complex impedance. They can also be written in polar form. Impedances in combination circuits like the RLC parallel circuit.

Complex Impedance for RL and RC
Complex Impedance for RL and RC

Resistance and Reactance

Resistance is fundamentally friction against the motion of electrons. It is there in all conductors to some extent (except superconductors!), and most notably in resistors. When the alternating current goes through a resistance, a voltage drop is formed that is in-phase with the current. Resistance is mathematically symbolized by the letter “R” and is measured in the unit of ohms (Ω).

Resistance and Reactance Circuit
Resistance and Reactance Circuit

Reactance is essentially inactive against the motion of electrons. It is present anywhere electric or magnetic fields are developed in proportion to an applied voltage or current, correspondingly; but most notably in capacitors and inductors. When the alternating current goes through a pure reactance, a voltage drop is produced – which is 90o out of phase with the current. Reactance is a mathematically symbolized by the letter “X” and is measured in the unit of Ohms (Ω).

Applications of Impedance

Impedance and resistance both have applications whether you consider it or not, both exist in your own house. Your house’s electricity is controlled by a panel that has fuses in it. When you go through an electrical surge, the fuses are there to interrupt the power so that the injury is minimized. Your fuses are similar to very high-capacity resistors that are capable of taking the blow. Without them, your house’s electrical system would fry and you would have to make it up from scratch

This problem can be solved thanks to impedance and resistance. Another situation in which impedance has importance is in capacitors. In capacitors, impedance is used to manage the flow of electricity in a circuit board. Without the capacitors controlling and adaptable electrical flow, your electronics that use alternating currents will either fry or go berserk. Since alternating current delivers electricity at a fluctuating pulse, there needs to be a gate that holds back all the electricity and lets it go smoothly so that the electrical circuit is not overloaded or underloaded.

In this article, we have discusses electric circuit theory and EIT (electrical impedance tomography) concepts and their working principles, complex impedance, use of complex impedance, complex impedance for RL and RC circuit concepts and reactance and resistance. Finally applications of electrical impedance. Furthermore, for any queries regarding this concept or electrical and electronics projects, please give your valuable suggestions by commenting in the comment section below. Here is a question for you, what are the applications of an electrical impedance?

Photo Credits:

  • Electrical Impedance bhs4
  • Electrical Impedance Tomography wikimedia
  • Complex Impedance for RL and RC phy-astr
  • Resistance and Reactance