Science
What is an electric circuit?
Quick answer
An electric circuit is a complete loop that electricity flows around. A simple circuit has a battery, wires and a component like a bulb. If the loop is broken, the electricity stops.
In one sentence
A circuit is a complete loop of wires and parts that lets electricity flow from a power source and back again.
Explained
Electricity only flows when there is a complete path with no gaps, a bit like a racetrack. If one piece of track is missing, the cars can't get round. In a circuit, the "cars" are tiny charged particles called electrons, and the battery is what pushes them.
A simple circuit needs:
- a power source, such as a battery (often called a cell)
- wires made of a conductor such as copper
- a component that uses the electricity, such as a bulb, buzzer or motor
Connect them in a loop and the bulb lights. Unhook one wire and it goes out.
A switch is a gap you can open and close. When it is "on", it closes the gap and current flows. When it is "off", it opens the gap and current stops.
There are two main ways to connect components:
- Series circuit: everything is in one loop. If one bulb breaks, they all go out. Adding more bulbs makes each one dimmer.
- Parallel circuit: each component has its own branch. If one bulb breaks, the others stay lit. This is how homes are wired.
Scientists draw circuits with simple symbols so anyone in the world can read them.
Examples
| Component | What it does | Simple symbol |
|---|---|---|
| Cell (battery) | pushes the current | a long and a short line |
| Bulb | gives out light | a circle with a cross |
| Switch | opens or closes the circuit | a line with a gap and a lever |
| Buzzer | makes a sound | a semicircle shape |
| Motor | spins | a circle with M |
lamp
robot
fan
Common mistakes
- "Electricity only needs one wire to the bulb." It needs a loop: from the battery, through the bulb and back to the battery.
- "More batteries are always better." More cells make bulbs brighter, but too many can burn out a bulb.
- "The current is used up by the bulb." The current is the same all the way round a series circuit; the bulb changes energy into light and heat.
Quick quiz
Electric circuits
Check what you know with 4 quick questions.
Question 1 of 4
Why won't a bulb light if one wire is loose?
Practise it
Try it
Build a circuit with a battery, a bulb and two wires, then test which materials complete the gap. Then try more physics activities.
Circuits and physics activities
For grown-ups
Related topics
Electricity
Electricity is the flow of tiny charged particles called electrons through a material. It powers lights, phones and machines, and it can come from batteries or the mains supply.
Materials
Materials are what objects are made from, such as wood, metal, plastic and glass. Each has properties, like being hard, bendy, waterproof or see-through, that suit it to some jobs.
Atoms
An atom is the tiny building block of all matter. It has a nucleus of protons and neutrons in the middle with electrons around it. The number of protons decides which element it is.
Forces
A force is a push or a pull. Forces can make things start moving, speed up, slow down, change direction or change shape. They are measured in newtons.
Friction
Friction is a force that acts when two surfaces rub or slide against each other. It slows things down and turns movement into heat, and it also stops us slipping.
Gravity
Gravity is the force that pulls objects towards each other. Earth's gravity pulls everything towards its centre, which is why things fall down and why the Moon orbits Earth.