Complete guide: What is an electrical circuit, how does it work, and how do you make one?

An electrical circuit is a closed path that allows electrical current (the flow of charge) to pass through, transporting energy. It is powered by a source (battery/the mains) that creates a 'pressure' (voltage) to push electrons through a wire (conductor) to a device that uses them (light bulb/motor). 

To make one, you simply need to connect the source to the device and complete the path back to the origin. If the circuit is broken, the flow of energy stops. 

Here is a complete guide to help you understand what they are, what types exist, how they work, and a step-by-step guide to building your own!

What is an electrical circuit?

An electrical circuit is a closed network of conductive elements that allows electrical energy to flow. Its main function is to channel electrons from a generation point (source) to a consumption point (load), where that energy is transformed into another useful form, such as light, heat, or mechanical movement.

For it to be considered a 'circuit', the path must be continuous. If the path is interrupted at any point, the flow stops. This is what we know as an 'open circuit'.

Examples of electrical circuits

For example, imagine the light in your bedroom. When you flick the switch, you are closing an electrical circuit. Electricity leaves the home's consumer unit (fuse box), travels through the wires to the bulb, and returns to the point of origin. The moment you turn off the switch, the circuit opens, and the current stops flowing, which is why the light goes out.

Another very simple example is a torch. When you put the batteries in and press the button, you complete the circuit, and the bulb lights up. If you remove a battery or the button is in the 'off' position, the circuit 'breaks' and it does not work.

How does an electrical circuit work?

The operation of a circuit is governed by physical laws, primarily the interaction between three magnitudes: voltage, current, and resistance.

The potential difference (voltage) is the force that pushes the electrons to move. Without a source to create this pressure, such as a battery or the mains supply, there is no movement. When the circuit is closed, the electrons travel through the conductors. Interestingly, although electrons actually move from the negative pole to the positive pole, by historical convention, current is said to flow in the opposite direction. This behaviour is summarised by Ohm's Law, which states that the current is proportional to the voltage and inversely proportional to the material's resistance:

V = R x I

What are the parts of an electrical circuit?

For a circuit to be functional, it must have the following elements:

• Generator (source): Provides the energy. Example: Batteries or alternators.

• Conductors: Materials (usually copper wires) that offer low resistance and act as a 'highway' for the electrons.

• Loads: Devices that consume the energy. Example: Light bulbs, motors, or resistors.

• Control devices: Allow you to control the flow of current. Example: A wall switch or a push-button.

• Protective devices: Prevent damage to the wiring or fires. Example: Fuses or circuit breakers (in the consumer unit).

What types of electrical circuits exist?

Depending on how the components are connected, the behaviour of the energy changes. Here is a quick comparison of the different types of electrical circuits:

Step by step: how to make a simple electrical circuit

This experiment is ideal for understanding the theory in practice.

Materials needed:

• 1 Battery (4.5V or 9V).

• 1 Small 6V light bulb (or an LED with its resistor).

• 2 Copper wires, stripped at the ends.

• Insulating tape or a small bulb holder.

Procedure:

1. Connecting the source: Attach the end of the first wire to the positive (+) terminal of the battery.
2. Connecting the load: Attach the other end of that wire to one of the bulb's contacts.
3. Closing the circuit: Take the second wire and connect it from the free contact on the bulb to the negative (-) terminal of the battery.
4. Result: As soon as the path is closed, the bulb will light up. If you want to add a switch, you will need to place it in the middle of one of the wires.