What circuits can do
The first person who wrote about his studies on electricity was a Greek called Thales who lived about two and a half thousand years ago. His work did not involve circuits or electric currents. It involved observations on a substance called amber. When he rubbed a piece of amber he found that it would pick up dust or even larger items such as straw and feathers. It appears that nobody else made studies on electricity until almost two thousand years later when an English scientist called William Gilbert found that when gemstones were rubbed they also behaved like amber. Amber and gemstones are small objects. It was not long before someone thought about what might happen if a large object could be rubbed. It was found that when a substance called sulphur was made into a ball about the size of a football, then spun round and rubbed, large sparks could be made. In fact some people made a living travelling around from town to town and entertaining people by putting on shows in which large sparks were made.

Sparks could not be used to make circuits but in 1799 Alessandro Volta, an Italian scientist, invented a device which produced a steady flow of electric current through a circuit. It was a battery. As soon as scientists learnt about Volta's battery they began to build their own and make investigations with them. In England, the scientist William Nicholson made a battery like Volta's battery. He connected a wire to each terminal then dipped the free ends of the wires into water. He discovered that bubbles of gas formed around the ends of the wires. When the bubbles were collected and tested, the bubbles from the end of one wire contained oxygen and the bubbles from the end of the other wire contained hydrogen. These are the two chemicals from which water is made.

Nicholson had used electricity to split up the substances from which water is made.
Another English scientist, called Humphrey Davy, learned of Nicholson's work and wondered if he could use electricity to split up the substances in other materials. He built a very large battery, which produced a large current, and tested a wide range of solutions and molten substances with it. It was not long before Davy began discovering metals, which were new to science. They formed tiny globules in the substances he tested.
While some scientists used current electricity to split materials apart, others investigated the link between electricity and magnetism. Experiments were done which showed that iron filings arranged themselves around a wire carrying electricity just as they do around a magnet. A compass needle, which is a magnet used to find North and South, was shown to move when a wire carrying a current passed through it. André Ampere, a French scientist, set up two wires side by side. One wire was fixed but the other was free to roll either towards or away from the other wire. When Ampere let currents flow in the same direction in both wires he found that the free moving wire rolled towards the fixed one. The wires attracted each other, just like magnets, which have opposite poles close to each other. When Ampere let the currents flow in opposite directions he found that the free moving wire rolled away from the fixed one. The wires repelled each other, just like magnets, which have similar poles close to each other.

An English scientist, called William Sturgeon, took Ampere's work on wires a stage further. He took a small iron bar which had been bent into the shape of a horseshoe and wrapped a wire around it. When he switched on the electric current he found that the horseshoe and coil had turned into a magnet which could lift a weight of just over four kilograms. Sturgeon had invented the first electromagnet.

When the American scientist Joseph Henry heard about Sturgeon's electromagnet he set out to build a larger one. He decided he could raise the electromagnet's power by increasing the number of coils of wire. Henry found that he had difficulty arranging the coils without them touching when the current would flow across the coils instead of round them. He solved the problem by taking one of his wife's silk petticoats and tearing it into strips. He spent many hours wrapping the wires in silk to insulate them so the current would flow correctly round the circuit. Henry was eventually successful in building a large electromagnet. It was so powerful that it could lift a weight of nearly three hundred and forty kilograms.

Today, we use circuits for thousands of different purposes. Just at this moment electricity is flowing through many tiny circuits in your computer to make the words you are now reading. Electric circuits are not just used in buildings but in vehicles of every kind from cars and boats to aeroplanes and spacecraft. It would be very difficult to imagine life without the use of electric circuits but up until two hundred years ago nobody had any idea about them.

Is amber related to the word electricity?
Yes, it is. The Greek word for amber is elektron. When William Gilbert discovered that other substances such as gemstones behaved like amber when rubbed, he called them 'electrics'.

Isn't it dangerous to bring electricity into contact with water?
Yes, it can be. If mains electricity, which is at 240 volts, is allowed to come in contact with water the current can flow through the water and harm anyone who is touching it. That is why it is important to make sure your hands are dry before you switch anything on or off. Electricity from a battery can be allowed to flow through water because the battery has a much smaller voltage than mains electricity.

Why is water split into hydrogen and oxygen by electricity?
Water is made from a chemical, which is made from hydrogen and oxygen atoms. They join together in groups called molecules. Each molecule of water has two hydrogen atoms and one oxygen atom. Scientists give the atoms different chemical letters. The letter for hydrogen is H and the letter for oxygen is O. The chemical name for water is H2O. You may have heard some people using this name. When electricity passes through the water it breaks up the water molecules and hydrogen is attracted to one wire and oxygen is attracted to the other.

Why don't the gases just go to the same wire?
When the electricity splits up the water molecule, two particles are produced. There are hydrogen particles, which lack electrons, and oxygen particles, which have more electrons than they need. One of the wires in the water can supply electrons and the other can remove them. This means that the hydrogen particles move to where they can get electrons and become atoms of hydrogen gas and the oxygen particles move to the wire where they can lose the electrons they do not need and becomes atoms of oxygen gas.

Why were Davy's metals new to science?
They had not been seen before. The reason for this was that they are substances that do not like to exist on their own. They like to join with other substances. When Davy used a strong electric current it ripped the metal atoms from the atoms of other substances. When this happened the atoms of the metal collected around one of the wires.

What metals did Davy discover?
Calcium, magnesium, potassium, sodium, barium and strontium.

Do electromagnets have any uses?
They have many uses. Large ones are used in scrap yards to lift old cars around. Small ones are found in doorbells and door chimes. An electromagnet is used in the switch which is used to turn on a car's engine. A large current is used to make the engine start up and the switch keeps the current away from the driver and prevents a shock.