Open Circuit vs Closed Circuit: What Is The Difference?

We know electric circuit is the route or the path that defines the flow of electric current. From the power source to the loads or devices that will require electric power.  A typical electric circuit encompasses of various components such as power source, loads and electronic components that control and determine the behavior of the circuit.

An electric circuit can either be open or closed. What is the difference between the two?

From a general point of view an open circuit is one that is literally “open” at one point of the circuit. This means that the path is broken at that point hence the electric current cannot complete a full path. The break in an open circuit can be due to the switch being turned off, a broken wire, or even a disconnected cable. Failure of an electronic component in the circuit can also lead to an open circuit.

A closed circuit is the complete opposite of an open circuit. It does not have any breaks along the whole path. The switch is in ON  and all the components are well functioning at their respective positions on the circuit. In short, everything in a closed circuit is in operation or is running as expected.

An example of an open circuit

Image source Brilliant

To bring a better and clear perspective, we will use a simple circuit diagram to define what an open circuit is. Our basic circuit has a DC power supply, a bulb that serves as a load, a resistor, and a switch.

When the switch is open, our circuit will be open as there will be no flow of electric current from the load to the bulb. The bulb will not light.

Similarly, removing the resistor from the circuit will open up the circuit as it will interfere with the flow of electric current from the  DC source to the load.

The circuit will also be open when we introduce an insulator at any point along the path. It will block the flow of current from the source to the load.

These are just some of the scenarios of opening up the circuit. There are many others which involve introducing different electronic components that will eventually interfere  with the flow of electric current.

Example of closed circuit

As we have already said, all the loads in a closed current are running. The image below will give you a clue of what we mean by a closed circuit:

Image source Science Shiffu

From the above diagram, you can see that the bulb is illuminating mainly because the circuit is closed. Otherwise, it will remain open as long as the path of the circuit interferes at any point.

Now transfer the above two examples of closed and open circuits to different kinds of applications. For instance, take a look at the working mechanism of the electrical components in a vehicle. For instance,  a vehicle’s ignition system will start up the engine when the circuit is closed and stop running the engine when the circuit is open.

Other differences

Let’s look at other key differences between open circuit and closed circuit

• Electric current: There is a smooth or uninterrupted flow of electric current in the closed circuit.  On the other hand, there is NO flow of electric current in an open circuit.
• Symbol: The two types are represented by different symbols in technical diagrams. An open circuit is represented by two brackets with nothing between them () while in closed circuit, there is something inside the bracket (.).
• Potential difference:  There is no potential difference in open circuit since there is no flow of electric charge or current from the source to the load. On the other hand,  there is a potential difference between the terminals of a closed circuit.
• Conductivity: In an open state, there will be no conduction of electric current. In a closed state, there is a conduction of electricity between the terminals.
• State of the circuit. An open circuit is in an OFF state while a closed circuit is in an ON state. These states are in relation to the position of the switch.

When to open a closed circuit

In as much as we have stated that a closed circuit is vital in ensuring that the loads or devices run as expected, there are numerous scenarios that make it necessary to open a closed circuit.

The most basic one is when you are not using the device or appliance. For example, when you don’t need the electric-powered light in the room, you will have no other option but to turn the switch off hence opening the circuit. The same applies to all other types of electric devices and appliances.

You will also need to open the circuit when doing repair and maintenance of the circuit. This is a basic safety measure that should be observed when working on any type of electrical engineering project.

You will also have to open the circuit in case of any electrical emergency. Let’s say there is fire and you would like to minimize its impact. Opening the circuit will be the best option.

In overall, there is no harm in opening a circuit. It is just a normal thing when it comes to dealing with electricity.

Why do we need a switch in a circuit?

At the heart of an open and closed circuit is the switch. It is a control tool that determines whether the electric circuit should remain open or closed. You will turn the switch on to open the circuit and off to close the circuit.

A switch is also a circuit’s safety tool. It can cut off the flow of electric current when necessary such as in case of an emergency. For example, if the load s overheating, you will find it necessary to switch off the circuit.

Conclusion

Knowing the difference between open circuit and closed circuit is important for anyone interested in electric projects. And when it comes to buying electronic components, ensure you get quality ones from reputable suppliers.

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