Learn the fundamentals of electricity, then build your own working circuits with our interactive circuit builder below!
Everything around you is made of tiny particles called atoms. Each atom has a center called the nucleus, surrounded by even tinier particles called electrons. Electrons don't circle the nucleus in neat paths like planets around the Sun — they spread out in fuzzy regions around it. In metals like copper, some electrons are held so loosely that they can drift from atom to atom. Electricity is what happens when these electrons move together in a flow — kind of like water flowing through a pipe.
When electrons flow through a material like a copper wire, we call that flow electric current. To get electrons moving, we need something to push them — that push is called voltage, and it comes from a power source like a battery.
Think of it like a water park: A battery is like the pump that pushes water up to the top of a water slide. The wires are like the slide itself — the path the water flows through. A light bulb is like a waterwheel along the path — it uses the water's energy to do something useful. And voltage is how high the pump pushes the water — more height means more energy!
Fun fact: Electrical signals travel incredibly fast through wires — often at a large fraction of the speed of light! The exact speed depends on the cable and the materials around it. Individual electrons, however, drift much more slowly — usually less than a millimeter per second. It's the electrical signal that travels quickly, like a wave passing through the wire.
Before we start building circuits, let's learn the important words scientists and engineers use when talking about electricity.
Every circuit is built from just a few basic parts. Here's what each component does and how it works in the circuit builder below.
There are two fundamental ways to arrange components in a circuit. Each has different properties — understanding the difference is a core skill in electronics.
Components are connected in a single loop, one after another. Current flows through every component in order. If one bulb burns out, the entire circuit breaks and everything turns off.
Components are connected on separate branches so current splits and flows through each path independently. If one bulb burns out, the others stay lit because their branch still works.
Did you know? Almost all household wiring uses parallel circuits. That way, each outlet and light works independently. Series circuits show up too: the batteries in a flashlight or TV remote are lined up in series, + to −, so their pushes add together — two 1.5 V batteries make 3 V. Try it yourself in the Double the Push challenge!
Our circuit builder is perfectly safe to experiment with, but real-world electricity can be very dangerous. Here are the most important safety rules.
Never touch exposed wires, outlets, or electrical equipment with wet hands. Ordinary water — from the tap, a pool, or even sweat — conducts electricity because it has minerals and salts dissolved in it. (Perfectly pure water is actually a poor conductor, but the water around you is never that pure.) Wet skin lets current pass into your body much more easily, making electrical shocks much more dangerous. Never stick anything into an electrical outlet, and always have an adult supervise any real electricity experiments. If you see a downed power line, stay far away and tell an adult immediately.
Use the tools below to place components on the grid, wire them together, and hit Simulate to watch electrons flow through your creation. Then try the challenges under the builder!
About this simulator: every bulb acts like a fixed 10 Ω resistor, and 100% brightness means one bulb on one 1.5 V battery — so extra batteries can push a bulb past 100%. Real bulbs change resistance as they heat up, and LEDs work quite differently, so real circuits won't match these numbers exactly.
Select a component from the toolbox and click on the grid to place it. Use the Wire tool to connect component terminals (the small circles). A complete circuit needs a battery, at least one load (bulb or resistor), and wires connecting them in a loop. Click Simulate to see electrons flow!