An Electric Circuit is simply an interconnection of circuit elements such as resistors, capacitors, voltage or current source etc. Depending on the type of circuit elements and the way they are connected, we can have different types of circuits. In this guide, we will explore the basic types of electric circuits.

Outline

Toggle## What is an Electric Circuit?

Assume you have a small electric bulb and a battery. To make the bulb glow, all you have to do is connect the two pins of the bulb to the positive and negative terminals of the battery. That’s it. You made a simple electric circuit. An Electric Circuit is an interconnection of different type of circuit elements such as an energy source, resistors, capacitors, inductors, transistors etc.

The energy from the source (which is the battery in the previous example) flows through the circuit elements (light bulb in this case) in the form of an electric current and a voltage appears across the terminals of the elements.

## Types of Circuits

Imagine we have two light bulbs and want to connect them to the battery. How do we connect them? What happens if we connect them back-to-back? Or can we connect them across the terminals of the battery at the same time?

The point of the above discussion is that depending on how you connect the circuit elements, you can have different types of circuits and accordingly the circuit parameters such as voltage and current of the individual element will vary.

For example, if we connect the two bulbs back-to-back and connect them across the battery, this is known as a Series Circuit. But if we connect both the bulbs across the battery at the same time, then it is known as a Parallel Circuit.

Are there only these two types of circuits? No, these two are the basic types of electric circuits and there are many more. The following is the list of different types of circuits that we frequently encounter in electric circuits.

- Open Circuit
- Closed Circuit
- Series Circuit
- Parallel Circuit
- Series – Parallel Combi Circuit
- Star Delta Circuit
- Linear Circuit
- Non-Linear Circuit
- Active Circuit
- Passive Circuit
- Unilateral Circuit
- Bi-Lateral Circuit
- AC Circuit
- DC Circuit

Let us now briefly understand about these different types of circuits.

### Open Circuit

In an electric circuit, if there is a break in the path for current to flow, then it is known as an Open Circuit. An open switch or a blown fuse will interrupt the flow of current and as result, makes the circuit an open circuit.

### Closed Circuit

For current to flow in an electric circuit, it must be a closed circuit. A closed circuit completes the electric circuit and provides a path for current flow. If we toggle the previous switch, it completes the circuit and makes it a closed circuit.

### Series Circuit

If we connect all the elements in a circuit in a back-to-back fashion, then the circuit is known as a Series Circuit. In a Series Circuit, there is only one path for the current to flow and as a result, the same current flows through all the circuit elements.

### Parallel Circuit

A Parallel Circuit is completely different than a Series Circuit. While there is only one common point between circuit elements in a series circuit, there are two common points in a parallel circuit. In a Parallel Circuit, the two terminals of both the circuit elements are connected together. As a result, the current in a Parallel Circuit can take more than one path to flow.

### Series – Parallel Combi Circuit

A Series – Parallel Combi Circuit, as the name suggests, consists of a combination of series and parallel circuits.

### Star Delta Circuit

Apart from series and parallel circuits, there are two more types of circuits that doesn’t fall into either of these categories. They are Star and Delta Circuits. If the elements are connected in a “Star” (Y or Wye) fashion, then it is known as a Star Circuit. On the other hand, if the elements are connected in a “Delta” (a triangle) fashion, then it is known as a Delta Circuit.

Star and Delta Circuit are very important in transformers and we also have formulas for converting between Star and Delta Circuits.

### Linear Circuit

A Linear Element is an electronic component that exhibits a linear relationship between the voltage and current i.e., their properties such as resistance, capacitance, inductance etc. is always constant. Some linear elements are: resistors, capacitors, inductors etc. If a circuit consists of only these linear elements, then the circuit is known as a Linear Circuit.

All Op-Amp based circuits such as Amplifiers, Integrators, Differentiators, Filters etc. are examples of Linear Circuits.

### Non-Linear Circuit

A non-linear element is an electronic component that exhibits a non-linear relationship between the voltage and current i.e., its resistance, inductance or capacitance is not constant. Diodes and Transistors are the two basic non-linear elements. Other examples include Iron Core Inductors and Transformers.

If the circuit consists of at least one non-linear element, then it is known as a Non-Linear Circuit.

### Active Circuit

An Active Circuit is an electric circuit that has an internal source of energy or returns energy to the source. Except diode circuits, all semiconductor circuits are active circuits.

### Passive Circuit

A Passive Circuit is an electric circuit that only takes energy from an external source but doesn’t return any energy to the source. All “RLC” circuits are passive circuits.

### Unilateral Circuit

A Unilateral Circuit is an electric circuit whose characteristics or properties change with the direction of flow of current or operation. A Diode as a Rectifier is a classic example of a unilateral circuit, where it rectifies only the positive cycle of the AC signal but not the negative cycle.

### Bilateral Circuit

In a Bilateral Circuit, the circuit characteristics or properties are the same irrespective of the direction of operation or the flow of current. A Resistive Circuit is a simple example of bilateral circuit. In complex circuits, a transmission line is a bilateral circuit.

### AC Circuit

If the main source of power in the circuit is AC, then it is known as an AC Circuit.

### DC Circuit

If the main source of power in the circuit is DC, then the circuit is known as a DC Circuit.

Apart from these basic circuit types, we can also classify circuits based on the circuit elements. The following is a list different types of circuits based only on its circuit elements.

- Resistive Circuit (contains only Resistors)
- Capacitive Circuit (contains only Capacitors)
- Inductive Circuit (contains only Inductors)
- RL Circuit (Resistive – Inductive)
- RC Circuit (Resistive – Capacitive)
- LC Circuit (Inductive – Capacitive)
- RLC Circuit (Resistive – Inductive – Capacitive)

The following image shows a collection of different combinations of above mention circuits.

## Conclusion

A basic knowledge about different types of circuits is an essential skill to have if you want to become a better engineer. We learned what is an electric circuit, what are the different types of electric circuits along with a simple schematic depicting each circuit type.