# Explaining the Electrical Impedance Formula

Electrical impedance plays a crucial role in the way electrical devices function. It is an important and popular concept in physics and electrical engineering. Impedance is the resistance put up by a circuit to an alternating current like an audio signal. In a resistive circuit, impedance and resistance are similar. The electrical impedance formula helps in determining a circuit’s opposition to a current when voltage exists.

Impedance is mostly used when a loudspeaker connects to an audio system. Although the concept of impedance is not fully understood, this concept is widely used in several engineering disciplines. As an important concept in electrical engineering, engineers use the electrical impedance formula to determine a lot of factors in electrical devices. This article describes a combined impact of electrical impedance in an entire circuit.

## What is Electrical Impedance?

Electrical impedance measures the opposition of a circuit to a current when there is voltage. It simply describes the opposition offered by a circuit to alternating or direct current. The symbol ‘Z’ denotes electrical impedance. Electrical impedance is usually measured in ohms. Impedance has both phase and magnitude.

The circuit’s frequency determines the opposition of electrical impedance to current. On the other hand, resistance (R) measures how much a substance opposes the passage of electrons among its atoms. Resistance is different from impedance as it contains only magnitude. It can simply be understood as impedance with a phase angle of zero.

Impedance may feature inductive reactance (XL), resistance (R) and capacitive reactance (Xc). Therefore, total impedance is simply the sum of capacitive reactance, resistance, and inductive reactance. Impedance explores the idea of resistance to an alternating current.

The electrical impedance formula is

Z=VI

Where Z is the electrical impedance measured in ohms

I is the electric current usually measured in amperes

V is the voltage measures in volts.

Electrical impedance affects the propagation of signals via a circuit board, the leakage of signals in undesired parts of a circuit board and how power exchanges between components. The effect of resistance and reactance in an AC circuit is usually termed as impedance. The resistance is the opposition of current while reactance opposes electric current flow as a result of frequency dependent elements such as capacitor inductor.

In an AC circuit, the opposition caused by reactance and resistance in the flow of AC is impedance. Therefore, the impedance of an AC circuit in a mathematical perspective is Z=R+- jX. In this case, X is the reactance and R is the resistance.

## How does Impedance Differ from Resistance?

Before we discuss the difference between impedance and resistance, we need to understand that impedance is related to alternating current while resistance is related to direct current.

Impedance and resistance are two different concepts. While the two concepts can be used in a confusing manner, there are completely different. Impedance measures the extent of opposition of the AC created as a result of capacitance and inductance. Frequency determines the extent of this opposition. Impedance is simply the sum of reactance and resistance.

Resistance, on the other hand, results from the collision of the electrons present in a conductor with the iconic lattice of the conductor. This in turn leads to electrical energy conversion into heat. One could denote that electrical resistance is simply the opposition to electric current. A good resistance changes with frequency.

Impedance is mainly used in alternating current (AC) circuits while resistance is mainly used in direct current (DC) circuits. Also, impedance occurs as a result of resistance and reactance while resistance occurs due to resistive elements.

While impedance has a magnitude and a phase angle, resistance has no phase angle and magnitude. Electric impedance shows energy stored and power dissipation when it is in an electromagnetic field while resistance only reveals power dissipation.

## How does Electric Impedance Work?

Electrical impedance is relevant when AC signal is the applied input signal. In a way, electrical impedance shares some properties with resistance. Also, this means the opposition to current flow. However, resistance is independent of frequency. For instance, if you have a simple resistor and you operate DC voltage, the resistance value won’t change in response to frequency.

A circuit’s impedance, on the other hand, changes in response to frequency since it has reactive elements such as the inductor and capacitor. In the case of the capacitor and the inductor, these elements offer a resistance referred to as reactance. The symbol X denotes reactance. Capacitive reactance, also denoted by symbol XC while inductive reactance is represented by the symbol XL.

The inductive reactance will have a value equal to jwL while the capacitance reactance has a value that is equal to 1/jwC. It is important to know that this reactance refers to the ratio between the electric current and the voltage. Therefore, if we consider the ratio of the current and voltage, this will amount to the reactance of the capacitor or inductor.

### How to Derive Expressions

From the above explanations, you will realize that the capacitive reactance and inductive reactance are dependent on frequency. This indicates that the value of reactance will change in response to frequency.

Let’s imagine your circuit has the resistive elements, the impedance is the total resistance the circuit provides. The symbol Z represents this impedance. Therefore, the total impedance will be the aggregate sum of the resistive element and also the reactive element. The total impedance will then be equal to R+jWL.

In some cases, it is denoted in the polar form. It indicates that there are some finite phase and finite magnitude. The magnitude of such impedance will be expressed as |Z|=R2 + X2 while the phase of the impedance will be expressed as =tan-1(X/R).

Just like the resistance, the impedance of a circuit is also a ratio of current and voltage. Therefore, if the impedance of any circuit is represented in this way, it indicates the voltage will clearly lead the current and the ratio of the current and voltage signal will provide the value of the impedance’s magnitude.

## Types of Electrical Impedance

Electrical impedance is available in two different types. These are the output impedance and input impedance.

Output impedance

For instance, when the circuit gives output voltage when we connect some load at the output terminal. Also, the output voltage must show up across the load’s two terminals. However, from this perspective, it will find some resistance in electric series.

Input impedance

This kind of impedance occurs when you connect some voltage source through the input terminals. When we look at the electric circuit from this opinion, the impedance in this electric circuit is what is known as input impedance. Therefore, input impedance is simply an impedance between the two terminals of an electric circuit.

## Applications of Electrical Impedance

Impedance is applicable in different scenarios. This concept even exists in your house. A panel which comprises fuses controls the electricity of your house. Therefore, when there is an electrical surge, the fuses will disrupt the power to prevent or minimize injury. These fuses work in a similar way with a high-capacity resistor. Without these fuses, the electrical system in your house would burn and this will result in paying more cost.
However, there is a good solution to this problem. All thanks to resistance and impedance. Impedance has its usefulness in capacitors. Impedance manages electricity flow in a printed circuit board. Without capacitors, your electronics that make use of alternating currents will burn or fry. This is because alternating current (Ac) supplies electricity at an unstable pulse. Therefore, there is a need for a gate to hold back the electricity and allow free flow so the electrical circuits isn’t too loaded or under loaded.

## Importance of Electrical Impedance

Electrical impedance plays a crucial role in the way electrical devices function. It is an important and popular concept in physics and electrical engineering. Impedance is the resistance put up by a circuit to an alternating current like an audio signal. In a resistive circuit, impedance and resistance are similar. However, in a situation of a reactive circuit that features inductors or capacitors, the frequency of the applied signal determine impedance.

For instance, the circuitry of an audio equipment is designed to make the impedance constant over the whole audio range. It might not be possible to achieve this as loudspeakers change in impedance at or close to the resonant frequency.

Input impedance is a collection of components inside an input jack must receive power from the signal fed in the input. If input impedance evaluates the amount of electrical current a circuit absorbs, the output impedance evaluates the amount of current supplied by an output.

## Conclusion

We have discussed electrical impedance, its concepts, formula, and working principles in this article. Also, we looked into the importance and applications of the electrical impedance formula. Electrical impedance affects the propagation of signals via a circuit board, the leakage of signals in undesired parts of a circuit board and how power exchanges between components. The effect of resistance and reactance in an AC circuit is usually termed as impedance.

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