How Electric Circuits Work

Electricity is everywhere

When you switch on a light, turn on a torch, or play with a toy that buzzes and flashes, you are using electricity. But how does flicking a tiny switch make a bulb glow all the way across the room? The answer is the electric circuit.

Let's discover what a circuit is and how it works. (For the very basics of where electricity comes from, you can also visit electricity basics.)

What is a circuit?

A circuit is a complete loop that electricity can flow around. Think of it like a race track. The electricity is like runners that must be able to go all the way round the track and back to the start without stopping.

The electricity that flows is called an electric current. A current can only flow if the loop is complete — with no gaps anywhere. If there is even one tiny break, the current stops at once and nothing works.

The parts of a simple circuit

A simple circuit has just a few parts, and each one has a job:

• The battery — this is the source of energy. It pushes the electric current around the loop, like a pump pushing water along a pipe.
• The wires — these are the paths the current flows along, joining everything together into a loop. They are usually made of metal inside.
• The bulb (or buzzer, or motor) — this is the part that does something useful. The bulb turns the electrical energy into light.
• The switch — this lets you open or close the loop to turn the circuit on and off.

Put them together — battery, wires, bulb — in a complete loop, and the bulb lights up!

Complete and broken circuits

This is the most important idea, so let's say it clearly:

• A complete circuit is an unbroken loop. The current flows, and the bulb lights up. ✅
• A broken circuit has a gap somewhere. The current cannot flow, so the bulb stays dark. ❌

If you unclip one wire, the loop is broken and the bulb goes out instantly. Clip it back, and the bulb glows again. The electricity needs the whole loop to do its job.

How a switch works

A switch is a clever little gap-maker. It is a part of the circuit you can open and close on purpose.

• When the switch is closed (pushed together), it joins the loop. The current flows — the bulb is ON.
• When the switch is open (pulled apart), it makes a gap in the loop. The current stops — the bulb is OFF.

Every light switch in your house works this way. Flicking the switch simply makes or breaks a loop, letting you control electricity with one finger.

Conductors and insulators

Why are wires made of metal and covered in plastic? Because of conductors and insulators.

• A conductor lets electricity flow through it easily. Metals like copper, iron and steel are good conductors. That is why the inside of a wire is metal.
• An insulator stops electricity from flowing. Plastic, rubber, wood and glass are insulators. That is why wires are coated in plastic — to keep the electricity safely inside.

You can test materials yourself by putting them into a gap in a circuit. If the bulb lights, the material is a conductor. If it stays dark, the material is an insulator.

A safety reminder ⚠️

Making circuits with a small battery (like a AA cell) and a bulb is safe and fun. But the electricity in wall sockets is completely different — it is hundreds of times more powerful and is very dangerous. Never poke anything into a socket or play with mains electricity or chargers. Always stay with the safe, low battery experiments.

Try it yourself! 🧪

Build a working circuit. Ask an adult to help you gather the parts. You need one AA or AAA battery, a small 1.5-volt bulb (the kind made for batteries), and two short pieces of wire (or even two strips of kitchen foil).

1. Connect one wire from one end of the battery to the bottom of the bulb.
2. Connect the other wire from the other end of the battery to the side of the bulb.
3. When the loop is complete, the bulb lights up! You have made a working circuit.
4. Now disconnect one wire. The bulb goes out, because the loop is broken.
5. Test materials: put a metal paperclip in the gap — the bulb lights (conductor!). Put a plastic ruler in the gap — the bulb stays dark (insulator!).

You have just built a circuit, made a switch with your fingers, and tested conductors and insulators. The electrical energy from the battery becomes light in the bulb — discover more about energy changing form in the many forms of energy.