6 of 7 lessons
Circuits
What you’ll learn about
Overview
Electric circuits are everywhere even though you might not notice them. Every electrical appliance you can think of contains an electric circuit. Below are some of the topics you'll learn about
- simple circuits
- how switches and torches work
- some of the useful components that go in circuits
- batteries
- circuit diagrams
And, when you've done all that... Build your own circuits with Circuit Builder.
Simple circuits
Electric current flows equally through all parts of the circuit. As the current flows through the bulb it lights up. The voltage produced by the battery pushes the current around the circuit.
Electricity flows best through good conductors like metals. The wires used in circuits are made of copper metal covered in plastic. Plastic is a good insulator.
Switches
If there's a gap in the circuit, the circuit isn't complete and so, electric current can't flow along the wire and because no electricity is flowing through the bulb, it doesn't light up.
So, if we want to stop the electric current flowing round a circuit we can disconnect the wire from the battery or make a gap in the wiring. But there's a better way - we can make a gap in the circuit using a switch.
How do switches work?
Inside a switch there are two strips of metal which are held apart by a spring. When the spring pushes the metal strips together so they are touching, we say that the switch is 'closed'. Electric current can then flow through the switch and around the circuit. When the switch is 'open' the metal strips are pushed apart so the current can't flow. The best way of making a gap in your circuit to stop current flowing is to put in a switch.
Circuit components
A component is a fancy name for a thing that goes in a circuit. A really simple circuit is made from one battery connected by wires to a single component. Really complicated circuits can have thousands of components!
There are lots of types of components - below are a few really useful ones.
You probably know some of these components already and you'll also know of some simple circuits. Some people have a door bell or buzzer to let them know when someone's at the door and some have a torch. These are both simple circuits.
Circuit diagrams
We don't draw circuit diagrams with colourful pictures of bulbs and buzzers.
Circuit diagrams use symbols to represent the components in a circuit.
...we draw a circuit diagram like this:
Short circuits
A short circuit happens when electric current can flow round a circuit from one terminal of the battery to the other without passing through any components. In a short circuit, the wire heats up and the battery will go flat.
Circuit challenges
Use Circuit Builder to try:
- making the torch circuit
- changing the single 1.5 volt cell to a 3 volt battery
- adding more bulbs to the circuit
Build your own electrical circuits!
How much do you know about electrical circuits? Test your knowledge from the syllabus and try out our circuit builder game.
More lessons in this series
Quick tips about electrical safety
Dangerous situations
To stay safe, make sure you switch off the electricity before you plug in or unplug anything.
Never plug too many electrical appliances into one socket. The wires may overheat and catch fire.
Never poke things into electric sockets - you could easily be electrocuted.
Cables buried under road or footpaths could be carrying electricity and could kill you.
Never go fishing near overhead lines. Electricity might be carried down the fishing line back to you. You could be electrocuted.
Never poke things into electric toasters. The wires inside are uninsulated - you could easily be electrocuted.
Electric cables are often hidden behind walls. Make sure you know what is behind it using a cable detector from a DIY shop.
Never fly a kite near an overhead line. Electricity might be carried down the string back to you.
Building sites often have a live electricity supply. Do not go near them or you could get hurt or be killed.
Do not climb pylons or wooden poles, electricity can jump gaps if you get too close. Also, graffiti can cover warning signs and put others at risk.
Always keep electrical appliances away from water. Water conducts electricity - you could easily be electrocuted
Never climb into electricity substations or poke sticks through the fence. The high voltage electricity could kill you.
Before you climb any trees, always check there are no overhead lines nearby. If you get too close to an overhead line, you could be electrocuted.
Take extra care when mowing the grass with an electric lawn mower. If you damage the wire, you could be electrocuted.
Never play in derelict buildings - the electricity supply may not have been disconnected. You could be electrocuted.
Never touch exposed wires inside streetlights. You could be electrocuted.
Never play on or around railway lines, they carry high voltage electricity and you could be seriously hurt or killed.
Untidy wires might be tripped over or get damaged. Always make sure they are kept tidied away.
Never take electric appliances into the bathroom. Water conducts electricity - you could easily be electrocuted.
Did you know?
In 15 minutes, the sun radiates as much energy onto Earth as all the people on the planet during an entire year. Just imagine if we could channel the sun's energy effectively!
In August 1887 the London Electric Supply Corporation commissioned Ferranti to build the first power station. Today our electricity supply is still based on the system that Ferranti designed.
What is a volt? And why is it called a volt? The volt measures electromotive force. It was named after the Italian inventor Alessandro Volta (1745-1827)
In the 1780s, Alessandro Volta invented the first battery - all because of Luigi Galvani's experiments with dead frogs.
Thomas Alva Edison 1847-1931 is one of the most successful inventors ever, applying for over 1,300 patents by 1910, mainly to do with electrical or mechanical development.
High voltage electricity is carried across the country by pylons and 'stepped down' for domestic use at substations. The National Grid supplies electricity all over the country.