Light from pencil lead - Graphite Lamp

Light from pencil lead - Graphite Lamp

Graphite combustion reaction: C + O2 = CO2

Graphite is poorly conductive substance. Current flows through graphite. With graphite resistance 0.019 Ω, begins to heat up, and then burn.

Electrical energy is changed into heat energy by sending electromagnetic waves. When metal atoms are introduced by heating in a state of agitation, then emit radiation at different wavelengths. This is a radiation covering a broad frequency range, the spectral maximum in the range attributable to the higher frequency (shorter wavelength), the higher the temperature of the body. A man sees a wave with a frequency of 1014 - 1015Hz.

What happens to the graphite in the presented video:
- A hot graphite emits light due to the flow of electric current.
- Electricity goes into thermal energy.
- Can replace graphite filament made ​​of tungsten (standard bulb) because tungsten has a high melting temperature (3665K), low evaporation rate and favorable spectral composition of the emitted radiation, so that the filament will burn more slowly than in the case of graphite filament (temp. melting 1000K)
- The light bulb filament cools quickly due to heat transfer by radiation.