Circuits

Three things are needed for an electric currentElectric current is a flow of electric charges (electrons). to flow in a circuitA collection of wires and electric components connected together in such a way that electric current can flow through them.:

the circuit must be complete - electric current can't flow if there are any gaps in the circuit
a batteryA battery is two or more electric cells joined together that can produce an electric current when connected to an electric circuit. or other power source is needed to provide the energy to push the electric current through the wires.
the battery must be connected correctly. One wire must be connected to the (+) positive terminal of the battery and the other wire must be connected to the negative (-) terminal of the battery.

Circuit diagrams

We use circuit diagrams to represent electrical circuits. This is the circuit diagram for a simple buzzer:

Simple buzzer circuit

The battery, switch and buzzer are represented by circuit symbols. You can find out more about circuit diagrams in the Power Up Under 11 area.

Did you know?

Electricity used at home is metered in 'units' or kilowatt hours (kWh). Each unit is the same as 1,000 watts of electricity used for 1 hour. 1 unit = 1kWh.
Fossil fuels won't go on for ever - oil could run out in 30 years.
Electric shock victims often can't let go of the thing that is passing the electric current into their body. That's because the electricity makes their muscles contract.
Michael Faraday (1791-1867) was the first person to create a way of generating a constant current of electricity. His invention led to the power stations we know today.
What is a watt? Why is it called a watt? It's a unit measuring electric power, named after James Watt (1736-1819).
Save energy - Make sure the dishwasher and washing machine are full before you turn them on and use the lower temperature settings.
Michael Faraday (1791-1867) is one of the most famous people involved in the discovery and harnessing of electromagnetic force.
Save energy - Don't forget to switch your TV and computer off when you have finished using them.
The first turbine engines were designed by Charles Parson (1854-1931). Today turbine engines used to generate electricity are still based on his designs.
Benjamin Franklin (1706-1790) developed the first lightning conductor after flying a kite in a thunderstorm. A spectacular but very dangerous experiment!
All electrical appliances are rated in watts (W) or kilowatts (kW) ( One kilowatt is the same as 1,000 watts). You can use the ratings to compare how much electricity they use.
In the 1780s, Alessandro Volta invented the first battery - all because of Luigi Galvani's experiments with dead frogs.
Fossil fuels won't go on for ever - coal could run out in 250 years.
In 1771 Luigi Galvani used electricity to make a dead frog's leg jump!
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.
Save energy - Finished playing on your games console or other equipment? Remember to switch off!
Today we still use words that Benjamin Franklin (1706-1790) introduced: battery, conductor, positive and negative charge, electric shock and electrician.
In 1800 Alessandro Volta built the world's first battery from discs of copper and zinc sandwiched between cardboard moistened with a salty water.
The ampere is named after André-Marie Ampère (1775-1836). He discovered many of the mathematical principles of electromagnetism.
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!
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 1831 Michael Faraday demonstrated electromagnetic force at the the Royal Institution in London, a famous centre for scientific education and research.
The Italian inventor Alessandro Volta (1745-1827) is best known for his work on electric current.
Modern power stations and steam turbines use the same engineering principles that James Watt (1736-1819) applied when he invented the steam engine.
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.
At Deptford in 1891, electrical engineer Sebastian Ziani de Ferranti (1864-1930) designed and built the first power station and supply network. His basic system is still used around the world.
Fossil fuels won't go on for ever - gas could run out in 40 years.
An electric eel can produce powerful electric shocks: up to 500 volts and one ampere of current (in other words, 500 watts).
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.
Save energy - Use energy efficient light bulbs and, when you are leaving a room empty, remember to turn the lights off.
Save energy - Boil just enough water for the number of hot drinks you want to make - that way you won't waste energy.

Circuits

Circuit diagrams

Danger

Did you know?