Learn with T.I.M.
How does a simple circuit work?
Why does a torch light up when you press the button? It's all about giving electricity a complete path. Here's how it works, in words an 8-year-old can follow.
A circuit is a path for electricity
Electricity is a kind of energy. It can make a light glow, a buzzer beep or a motor spin. But it can only do that if it has a complete path to travel along. That path is called a circuit.
A simple circuit has three main parts:
- A battery. It gives the energy. One end is positive (+) and the other is negative (−).
- A path. Wires, or tape with metal in it, carry electricity from one side of the battery round to the other.
- Something to power. A light, a buzzer or a motor sits on the path and uses the energy.
Open or closed?
When the path is complete, from the battery all the way round and back again, we call it a closed circuit. Electricity flows and the light turns on.
If there is a gap anywhere, it is an open circuit. Electricity can't jump across the gap, so nothing happens. A switch is simply a clever way to open and close that gap whenever we like.
Try it: close the switch
Small classroom batteries are safe for experiments like this. Never play with power points or plugs at home.
Conductors and insulators
Some materials let electricity flow through them easily. These are called conductors. Most metals, like copper, aluminium and steel, are good conductors. That's why wires have metal inside.
Other materials hardly let electricity through at all. These are insulators, like plastic, rubber, paper and wood. Wires are often covered in plastic, so electricity stays on its path and our fingers stay safe.
Try this in our Discovery Zone: put different materials in the gap and see which ones make the light turn on.
Why do LEDs have a long leg and a short leg?
An LED is a tiny light that only works one way round. Its longer leg connects towards the positive (+) side of the battery. If it is put in backwards, it simply stays dark. Nothing is broken, it just needs turning round.
One path or many?
When everything sits on one single path, a break anywhere stops the whole circuit. In a parallel circuit, each light has its own path, so if one light goes out the others keep shining. Our Traffic Lights project uses this idea.
Watch T.I.M. build a circuit
Electricity and circuits · 0:52
How a Circuit Works with T.I.M.
Why does a light turn on? T.I.M. builds a simple circuit with a battery, copper tape and an LED, then finds the gap that stops it working.
- A battery has a positive and a negative side
- Copper tape makes a path for electricity
- Open circuit: no light. Closed circuit: light!
Stay safe
The small batteries used in classroom projects are safe for experiments like these. Mains electricity from power points is very different and dangerous, so never experiment with plugs, power points or household wiring.
