Many electrical appliances used at home are lamps or heaters. In a lamp, electrical energy is transferred as light and heat. There are different types of lamps, including:
- tungsten filament lamps
- discharge tube lamps
In a tungsten filament lamp the energy is transferred in the resistance wire which makes up the filament. If you look at it closely, you will see the filament glowing but it also gives off a lot of heat. Of the electrical energy that goes into the lamp as little as 10% is transferred as light and up to 90% as heat.
An electric heater operates in the same way as a filament lamp in that the energy is transferred (from electrical to heat in this case) in a resistance wire, often called the element.
In a discharge tube the energy is transferred in the gas inside the tube.
A discharge tube lamp is more efficient than a filament lamp because:
- more of the electrical energy is transferred as light
- less of the electrical energy is transferred as heat