Thomas Edison was the inventor of the modern day incandescent light bulb. Incandescence means light is being produced through heat. The filament inside the light bulb is made from carbon and as the carbon is being vaporized, light is emitted. The glass casing on the light bulb allows the filament to burn longer, by reducing its exposure to oxygen.
This experiment replicates the modern day incandescent light bulb by using graphite from pencils as the carbon filament . Graphite will conduct electricity, and if enough electricity is run through a mechanical pencil ‘lead’ it will heat up and start to glow.