When the circuit closes, that means all cables are connected properly, the potential difference (voltage) applied to the circuit from the battery forces the free electrons to move from the point with the low potential to the one with high potential that means from the negative pole of battery to the positive one. This flow of electrons is called electric current.
The light bulb (incandescent lamp) operates as the light bulbs that we use at home. It consists of a thin glass wall. Inside the glass are inert gases such as nitrogen and argon. In the centre there is a very thin wire (filament) made of tungsten. Tungsten is a metal that melts in an extremely high temperature. When electricity passes through the wire, it becomes warm. As the temperature increases the wire starts illuminating. This illumination is the light.
The energy thus is transformed from electrical to thermal (heat) and then from heat to electromagnetic radiation (heat and light).
The incandescent bulb was invented in England by Joseph Swan in 1878 and independently (a year later) by Thomas Edison.
How much energy is used by a light bulb?
You need:
1 light bulb
2 pieces of cable
1 battery 4.5 Volt
A 9 Volt battery can be used. In this case appropriate light bulbs should be used too, else they will be destroyed.
AA or LR6, or any other cylindrical battery can be used; in this case a battery holder is necessary.
© 2003-2010 Despina M. Garyfallidou Athens-Greece
