This web application is specifically designed for the best experience on Google Chrome.
Please open this site in Chrome to continue.
If you don't have Chrome, you will be redirected to the app store.
An electrical network is an interconnection of various electrical components like resistors, capacitors, inductors, and energy sources. To effectively analyze, design, and troubleshoot these networks, it's crucial to understand how they are classified. This classification helps engineers apply the correct theorems and analysis methods.
Based on their properties and components, electrical networks are primarily categorized using four different criteria:
1. Linearity: Based on whether the circuit characteristics are linear or not.
2. Direction of Current: Based on whether the components allow current to flow in one or both directions.
3. Energy Sources: Based on the presence or absence of an energy source.
4. Component Separability: Based on whether the circuit elements can be physically separated.
Let's explore each of these classifications in detail.
This classification depends on the relationship between voltage and current in the circuit elements.
A linear network is one whose parameters (like resistance, inductance, and capacitance) remain constant regardless of any changes in voltage or current.
Key Characteristics:
Linear V-I Relationship: The voltage across an element is directly proportional to the current flowing through it. This relationship graphs as a straight line passing through the origin.
Obeys Ohm's Law: Linear circuits strictly follow Ohm's Law.
Principle of Superposition: The superposition theorem is applicable to linear networks.
Examples of Linear Elements: Resistors (R), Inductors (L), and Capacitors (C).
If a network contains at least one non-linear element, it is called a non-linear network. In these circuits, the parameters change with the applied voltage or current.
Key Characteristics:
Non-Linear V-I Relationship: The relationship between voltage and current is not a straight line.
Does Not Obey Ohm's Law: These networks do not follow Ohm's Law.
Superposition is Not Applicable: The principle of superposition cannot be applied here.
Examples of Non-Linear Elements: Diodes, transistors (BJT, JFET, MOSFET), and other semiconductor devices.
This classification is based on whether the circuit's behavior changes when the direction of current is reversed.
A unilateral network is one in which the properties change with the direction of current. It essentially allows current to flow effectively in only one direction.
Key Characteristics:
One-Way Conduction: Current flows easily in the forward direction but is heavily restricted in the reverse direction.
Asymmetrical V-I Characteristics: The V-I graph is not identical in the first and third quadrants. The circuit behaves differently when the voltage polarity is reversed.
* Examples of Unilateral Elements: Diodes and Transistors.
A bilateral network is a circuit whose characteristics remain the same regardless of the direction of the current.
Key Characteristics:
Two-Way Conduction: It allows current to flow with equal ease in both directions.
Symmetrical V-I Characteristics: The V-I graph is identical and symmetrical in the first and third quadrants. Reversing the voltage polarity does not change the magnitude of the current.
* Examples of Bilateral Elements: Resistors, Inductors, and Capacitors.
This is one of the most fundamental classifications, based on whether a network can supply energy.
An active network is an electrical network that contains at least one energy source, either a voltage source or a current source. These networks can deliver energy to the circuit.
Key Characteristics:
Contains an Energy Source: Must have a component that supplies power (e.g., a battery, generator, or operational amplifier).
Can Amplify Signals: Active components can provide power gain.
* Examples of Active Elements: Voltage sources, current sources, batteries, and transistors (in certain configurations).
A passive network is an electrical network that does not contain any energy sources. It consists solely of passive components that either dissipate or store energy.
Key Characteristics:
No Energy Source: Contains only passive elements.
Cannot Amplify Signals: These networks cannot provide power gain and typically cause a loss of signal power (attenuation).
* Examples of Passive Elements: Resistors (dissipate energy), Inductors (store energy in a magnetic field), and Capacitors (store energy in an electric field).
This classification relates to the physical size of the components compared to the wavelength of the signals flowing through them.
A lumped network is one where all the circuit elements (R, L, C) are assumed to be concentrated or "lumped" at a single point, meaning they are physically separable. This assumption is valid for low-frequency applications where the wavelength of the signal is significantly larger than the physical dimensions of the circuit.
Key Characteristics:
Physically Separable Elements: You can identify and separate each resistor, capacitor, and inductor.
Kirchhoff's Laws are Applicable: Kirchhoff's Current Law (KCL) and Voltage Law (KVL) can be directly applied.
* Example: Most standard electronic circuits on a PCB.
A distributed network is one where the circuit elements are not separable and are distributed throughout the length of the network. This is typical in high-frequency applications, like microwave circuits, where the signal wavelength is comparable to the circuit's physical size.
Key Characteristics:
Inseparable Elements: The resistance, inductance, and capacitance are spread out and cannot be isolated.
Kirchhoff's Laws are Not Directly Applicable: Analysis requires solving Maxwell's equations or using transmission line theory.
* Example: A transmission line, which has resistance, inductance, and capacitance distributed along its entire length.
| Basis of Classification | Type 1 | Type 2 | Key Difference |
| :--- | :--- | :--- | :--- |
| Linearity | Linear Network | Non-Linear Network | V-I graph is a straight line vs. a curve. |
| Directionality| Bilateral Network| Unilateral Network| Conducts equally in both directions vs. one direction. |
| Energy Source | Active Network | Passive Network | Contains an energy source vs. contains no energy source. |
| Separability | Lumped Network | Distributed Network| Components are physically separate vs. spread out. |
Q1: Can a circuit be both non-linear and bilateral?
Yes. An example is a varistor, whose resistance changes with voltage but behaves the same way for both positive and negative voltages, making it non-linear but bilateral.
Q2: Is a transformer an active or passive element?
A transformer is a passive element. While it can step up or step down voltage, it cannot create energy or provide power gain. It transfers power from one circuit to another through magnetic induction.
Q3: Why are transmission lines considered distributed networks?
Because the inherent resistance of the wire, the inductance due to the magnetic field, and the capacitance between the conductors are all spread out along the entire length of the cable, not concentrated in one spot.
Q4: What is the most common type of network used in basic circuit analysis?
For introductory circuit analysis (like courses using Kirchhoff's laws), we almost always deal with Lumped, Linear, and Bilateral networks, which may be either active or passive.
