Table of Contents

## Impedance, Resistance, Reactance, Admittance, Conductance, Susceptance, and Their Types Explained

__IMPEDANCE :__

__“Impedance is the total resistance/opposition offered by the circuit elements to the flow of alternating or direct current!”__

__OR__

__“The impedance of a circuit is the ratio of the phasor voltage (V) to the phasor current (I)”__

It is denoted by Z.

Z=V/I

As a complex quantity, we can write it as:

Z=R+jX

It is a vector (two-dimensional) quantity consisting of two independent scalar (one-dimensional) phenomena: resistance and reactance!

**RESISTANCE:**

__“Resistance of an element denotes its ability to resist the flow of electric current”__

OR

__“It is a measure of the extent to which a substance opposes the movement of electrons among its atoms”__

It is denoted by R.

The more easily the atoms give up and/or accept electrons, the lower the resistance, which is measured in ohms.

It is observed with alternating current (AC) and also with direct current (DC).

__Types of Resistance:__

· **HIGH RESISTANCE **:

Substances with High-resistance are called insulators or dielectrics and include materials such as polyethylene, mica, and glass.

· **LOW RESISTANCE:**

Substances with low resistance are called electrical conductors and include materials such as copper, silver, and gold.

· INTERMEDIATE RESISTANCE:

Substances with intermediate levels of resistance are called semiconductors and include materials such as silicon, germanium, and gallium arsenide.

## REACTANCE:

t is denoted by X.

It is expressed in ohms.

It is observed for AC (alternating current), but not for DC (direct current).

__TYPES OF REACTANCE:__

· **INDUCTIVE REACTANCE:**

When AC (alternating current) passes through a component that contains reactance, energy might be stored and released in the form of a magnetic field which is known as inductive reactance.

It is denoted by +*jX*_{L}

· **CAPACITIVE REACTANCE:**

When AC (alternating current) passes through a component that contains reactance, energy might be stored and released in the form of an electric field which is known as capacitive reactance.

It is denoted by –*jX*_{C}**EXPLANATION:**

Reactance is conventionally multiplied by the positive square root of -1, which is the unit imaginary number called the *j operator*, to express *Z* as a complex number of the form *R* + *jX*_{L }(when the net reactance is inductive) or *R* – *jX*_{C} (when the net reactance is capacitive).

__ADMITTANCE :__

__“Admittance is the allowance of circuit elements to the flow of alternating current or direct current “.__

OR

* “It is the inverse of impedance” *It is denoted by Y.

We can write as:

Y=1/Z=I/V

As a complex quantity, we can write it as:

Y=G+jB

Admittance is a vector quantity comprised of two independent scalar phenomena: conductance and susceptance

**CONDUCTANCE:**

__”Conductance is the ability of an element to conduct electric current.”__

__OR__

* “It is the inverse of resistance” *It is denoted by G.

G=1/RThe more easily the charge carriers move in response to a given applied electric potential, the higher the conductance, which is expressed in positive real-number (Siemens) or (Mhos).

Conductance is observed with AC and also with direct current DC.

**SUSCEPTANCE:**

__”Susceptance is an expression of the readiness with which an electronic component, circuit, or system releases stored energy as the current and voltage fluctuate”__

OR

* “It is a reciprocal of reactance” *It is denoted by B.

B=1/XSusceptance is expressed in the imaginary number Siemens.

Susceptance is observed with AC, but not for DC.

__TYPES OF SUSCEPTANCE:__

**INDUCTIVE SUSCEPTANCE:**When AC (alternating current) passes through a component that contains susceptance, energy might be stored and released in the form of a magnetic field which is known as inductive susceptance.

It is denoted by –*jB*_{L}**CAPACITIVE SUSCEPTANCE:**When AC (alternating current) passes through a component that contains susceptance, energy might be stored and released in the form of an electric field which is known as capacitive susceptance.

It is denoted by +*jB*_{C}

**EXPLANATION:**

Admittance is the vector sum of conductance and susceptance. Susceptance is conventionally multiplied by the positive square root of -1, the unit imaginary number called symbolized by *j* , to express *Y* as a complex quantity *G* – *jB*_{L} (when the net susceptance is inductive) or *G* + *jB*_{C} (when the net susceptance is capacitive).

In parallel circuits, conductance and susceptance add together independently to yield the composite admittance. In series circuits, conductance and susceptance combine in a more complicated manner. In these situations, it is easier to convert conductance to resistance, susceptance to reactance, and then calculate the composite impedance.

__Impedance & Admittance:__

ELEMENT | IMPEDENCEZ=V/I | ADMITTANCE = I/V |

R | ZR= R | YR= 1/R |

L | ZL= jwL | YL= 1/jwL |

C | ZC= 1/jwC | YC= jwC |

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