Using electricity for heat
Imagine it is a cold morning and you have just got up. You go into the living room and turn on an electric fire. You go away to make your breakfast and when you come back the room is nice and warm. You are very lucky. It wasn't so easy for people growing up in the early to mid twentieth century. They had to make a real fire, which was a much harder task.

In those days a living room had a fireplace which had a chimney. There was a grate in the fireplace. On the grate you set screwed up pieces of newspaper then put several sticks about fifteen centimetres long and two centimetres high and wide over the newspaper. These pieces of wood were called firewood. On top of the sticks you placed lumps of coal and then lit the paper. The flames from the paper licked round the firewood and set it alight. Once the firewood was burning its heat made the coal catch fire. The smoke from the coal and some of the heat escaped up the chimney and the rest of the heat spread out through the room and warmed it up. Once the fire was alight your duties were not over. Eventually the coal would begin to burn down and you would add more from a container called a coalscuttle, which was kept by the fire. You could add the coal with a scoop or a pair of tongs. Sometimes lumps of coal stuck together and made the fire burn less well. When this happened you used a metal rod called a poker to break up the lumps. If the fire looked as if it was about to go out you used a pair of bellows to blow air over the embers and make them burst into flame again. When an electric fire was installed none of this work was needed so you can imagine how pleased people were to have one in their home.

An electric fire produces heat in a much less messy way than a coal fire. This is how it does it. All substances are made from particles called atoms. Inside an atom are even smaller particles. Some of these particles are called electrons. When a voltage is applied to a metal wire some of the electrons move along the wire and make a current of electricity. When a current of electricity flows though a wire, the electrons rub and bump against the atoms and these actions cause the atoms to release heat. If the wire is thick, there is plenty of room for the electrons to move and the atoms are not greatly rubbed and bumped. This means that little heat is given out. However, if a wire is thin, there is very little room for the electrons to move about and atoms are greatly rubbed and bumped. This means a thin wire gives out much more heat than a thick wire. If a wire is short there are not many atoms in the path of the electrons so few are rubbed and bumped and little heat is given out. However if a wire is long, there are a great number of atoms in the path of the electrons and they are rubbed and bumped and give out great heat. Scientists used these facts to design an electric fire. They made a long thin wire and wound it into a coil to save space. The wire was made from a metal called nichrome, which would not melt or snap when it was heated for long periods. When an electric fire is switched on, the electrons rub and bump the atoms of the metal as they make their long journey through the thin wire and so much heat is given out that the wire glows a dull red colour.

When you think an electric fire has warmed the room enough you can simply switch it off. The electrons stop moving instantly. The atoms are no longer rubbed and bumped and the wire coil cools down. Later if you feel the room is too cold you can switch it on again.

Things were not that simple when you had a coal fire. At the end of the day you would let it die down and put a fireguard in front of it. The fireguard was a metal mesh about half a metre high. It stopped sparks and small lumps of coal flying out of the fire onto the carpet. In the morning you would have to rake out all the ash and clean the fire grate before you could lay another fire. This may seem so strange that you may want to ask somebody about it. Just ask someone you know who is about sixty years of age. They could probably tell you more about the time before there were electric fires.

What is coal?
It is a black rock made from fossil plants that lived many millions of years ago. When it burns it breaks up to form ash. Sometimes it breaks up with such force that small lumps of coal fly apart. The fireguard was put in front of the fire to catch these lumps when people were out of the room.

Do people still have coal fires today?
Some people do but most people either have gas fires or electric fires.

Does a coil of wire which gives out heat have a name?
Yes, it does. It is called a heating element.

Why is there a shiny piece of metal behind the heating element in an electric fire?
Heat is a form of energy that can move through the air as waves. Light is another form of energy that is in the form of waves. When light strikes a mirror it is reflected. In a similar way when the heat waves from the element strike the shiny metal surface they are reflected into the room. This makes the electric fire more efficient.

Does a convector heater use electricity?
Yes, it does. The heating element is near the bottom of the heater. When it is switched on it warms the air around it. The warm air rises out of the top of the heater and cooler air passes into the heater from below.

Where else can heating elements be seen?
There are heating elements in a toaster and in a hair drier. The heat from the elements in the toaster warms the surface of the slices of bread and turns them brown. In a hair drier there is also a motor, which drives a fan. The fan pushes air over the element and warm air shoots out of the hair drier to dry your hair.

Can heating elements be used to heat water?
Yes, they can, but they are enclosed in a metal case. This case is watertight. This means that the element cannot come into contact with the water. If it did, the current could flow from the element through the water to the rest of the container, such as a kettle, and give a shock (perhaps a fatal one) to anyone who touched it.

Where are elements used to heat water?
They are used in electric kettles and irons. They are used in an immersion heater to heat the water for the hot tap in the home. They are used in shower units to provide the hot water.

Where else are heating elements found?
They are found in electric cookers, electric blankets and in slow cookers. They are not found in microwave ovens. The food in a microwave oven is heated by microwaves, which rub the particles in the food together to make them hot.