Basic electrical circuits. Essential elements

24/03/2026

Online simulations of basic electrical circuits on this page serve as an introduction to our collection of thematic units on electric circuits. You’ll discover some of the main components—like batteries and switches—as well as key concepts such as open and closed circuits or short circuits.

What is a basic electric circuit?

The basic electric circuits introduced in this first Thematic Unit consist of just four elements: a DC power source (battery), a light bulb, wires, and a switch. The interactions are intentionally limited to two actions: opening or closing the circuit with the switch, and adjusting the battery voltage.

Battery

The battery provides the energy needed for electric current to flow through the circuit. In these simulations, it acts as a direct current (DC) power source, meaning it pushes electrons in a single, constant direction. You can adjust its voltage to see how it affects the behavior of the other components. It’s the starting point of the electric flow and lets you safely experiment with different voltage levels.

Light bulb

The light bulb acts as a visual indicator of current flow: if it lights up, the circuit is closed and current is flowing; if it stays off, something is blocking the flow. In these simulations, the bulb’s brightness changes with the current intensity, allowing you to intuitively observe how the electrical effect varies depending on the circuit configuration.

Wires

Wires connect the different components and allow current to flow between them. Although they have no resistance in the simulation, their layout is key to closing the circuit or creating situations like short circuits. Manipulating the wires is the most direct way to build, modify, or interrupt the current path.

Switch

The switch lets you open or close the circuit easily. In the simulations, just click on it to change its state. It’s the ideal component to introduce the concept of open and closed circuits, and to observe how a simple break can completely stop the current flow.

Explore the exciting STEM world with our free, online, simulations and accompanying companion courses! With them you’ll be able to experience and learn hands-on. Take this opportunity to immerse yourself in virtual experiences while advancing your education – awaken your scientific curiosity and discover all that the STEM world has to offer!

Basic Circuit Simulations

Bulb
Switch
Short circuit
Two bulbs

Simple circuit with a battery and a bulb

This simulation lets you build the simplest possible circuit: a battery connected to a bulb with two wires. If the circuit is closed, the bulb lights up. If any connection is missing, nothing happens. Try connecting the wires in order and see when the bulb turns on; disconnect one wire and see what changes; or adjust the battery voltage and observe how the bulb’s brightness varies. This simulation is ideal for confirming that current only flows in a closed circuit and that the battery is the source driving that flow.

Circuit with a switch

This simulation adds a switch to the basic circuit. Now you can open or close the circuit without disconnecting any wires. When the switch is closed, current flows and the bulb lights up. If you open it, the circuit breaks and the bulb goes out. Try toggling the switch and observing the immediate effect on the bulb, change the battery voltage and see if brightness varies when the switch is closed, or leave the circuit open and confirm that no current flows even if everything is connected. This simulation is great for introducing the concept of open and closed circuits in a visual and controlled way.

Circuit with a short circuit

In this simulation, you can create a short circuit by connecting the two ends of the battery directly with a wire, without any component in between. When you do this, current flows through a very low-resistance path and the battery overheats to the point of catching fire—visually showing the danger of a short circuit. Try closing the switch and see what happens, change the battery voltage to check if the effect intensifies, or open the switch to interrupt the current. This simulation lets you safely observe what happens when a circuit is closed but no load is connected.

Circuit with two bulbs

This simulation lets you connect two bulbs in series, one after the other, within the same circuit. When you close the switch, current flows through both bulbs before returning to the battery. You’ll see that both light up, but with less brightness than when there’s only one. If you disconnect either bulb, the circuit breaks and both go out. This simulation is useful for exploring how components behave when they share the current along a single path.

Giants of science

“If I have seen further, it is by standing on the shoulders of giants”

Isaac Newton

James Clerk Maxwell

1831

–

1879

James Clerk Maxwell formulated Maxwell’s equations, unifying electricity and magnetism and predicting electromagnetic waves

“Thoroughly conscious ignorance is the prelude to every real advance in science”

André-Marie Ampère

1775

–

1836

André-Marie Ampère formulated the theory of electromagnetism, establishing the mathematical foundations linking electricity and magnetism

“Science is the explanation of the complex by the simple”

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Giants of science

“If I have seen further, it is by standing on the shoulders of giants”

Isaac Newton

James Clerk Maxwell

1831

–

1879

James Clerk Maxwell formulated Maxwell’s equations, unifying electricity and magnetism and predicting electromagnetic waves

“Thoroughly conscious ignorance is the prelude to every real advance in science”

Michael Faraday

1791

–

1867

Michael Faraday discovered electromagnetic induction, conducted pioneering experiments in optics (Faraday effect), and established fundamental principles of electrochemistry.

“Nothing is too wonderful to be true”

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Principles of Modeling, Simulations, and Control for Electric Energy Systems

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Test your knowledge

What is a basic electric circuit, and why does it form the foundation of all more complex electrical systems?

A basic electric circuit is a closed path that allows electric current to flow from a power source, through a conductor, into a device that uses the energy, and back to the source. This continuous loop is essential because current can only flow if the path is unbroken. The reason this structure is fundamental is that every electrical system—whether it’s a household installation, an electronic device, or an industrial network—is built from this same principle. Even the most sophisticated circuits are essentially combinations of sources, conductors, loads, and control elements arranged in different ways. Understanding the basic circuit provides the conceptual framework needed to analyze how energy is delivered, how components interact, and how electrical systems behave under different conditions.

How do the main components of a basic circuit—power source, conductors, load, and switch—interact, and what role does each one play in the system’s operation?

The power source supplies the electrical energy that drives the movement of electrons. Conductors provide the pathway that allows the current to travel through the circuit. The load, such as a lamp or motor, converts electrical energy into another form—light, heat, or mechanical motion. The switch controls whether the circuit is open or closed: when it is closed, the current flows; when it is open, the current stops. These components work together to create a controlled and functional system. If any one of them fails or is incorrectly connected, the circuit cannot operate properly. Their coordinated interaction ensures that energy is delivered efficiently and safely to the device that needs it.

Why does the current stop flowing when I open the switch? Does it really make sense that “just a tiny gap” stops everything?

Yes, it makes perfect sense. Electric current requires a completely closed path to flow. When the switch opens, even if the gap is very small, the path is broken and electrons can no longer complete the loop. It’s similar to cutting a circular racetrack: even a small break prevents the cars from going around.

What happens if I connect the wires incorrectly in a basic circuit? How come the components don’t work even if they’re not damaged?

If the wires don’t form a complete loop or if the load isn’t properly placed between the positive and negative terminals of the source, the current has no path to follow. Even if the components are in perfect condition, a single incorrect connection interrupts the circuit. That’s why following the basic structure—source → conductor → load → conductor → source—is essential for the circuit to function.

How come a simple battery can light a bulb? Shouldn’t it need “more energy” to do that?

A battery provides enough voltage to push electrons through the circuit and into the filament of the bulb. The filament has resistance, which causes electrical energy to transform into light and heat. Even though a battery is small, it is designed to supply the right amount of energy for low‑power devices. As long as the bulb is meant for that voltage, the battery is more than capable of powering it.