Flourescent lighting
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Why does my new fluorescent light take five minutes to reach it's total brightness? In many countries that are driven to improve their pollutive emissions fluorescent light bulbs have now become the norm. The formerly used tungsten light bulbs
are called so because of a tungsten filament used in construction.
One of the first lessons taught to electricians is Ohm's law which states that the current flowing through a device is inversely proportional to its electrical resistance. Unfortunately such an important discovery (like many others) was given the title of a 'LAW' of the physics of electricity which from that point on retarded the thinking of many scientists to follow. The title of 'LAW' infers that the theory is in compliance with all other laws and can not be disproven and so not a great many of people tried to disprove it.
As time progresses and new discoveries unlock old mysteries we find that alot of previously cemented laws fall to pieces under certain conditions. For example quantum tunneling has proven that electrons can pass straight through matter, from one side to the other. If we think of an electron as a very small piece of matter then we can now think on a larger scale such as a boy bouncing a basketball against a wall. When electrons are continually slammed into a membrane, certain electrons are seen to bounce back but occasionally one passes right through the solid membrane! To find out more about this read about the 'uncertainty principle'. Now back to fluorescent lighting.
Ohm's law was a great break through and vastly important when talking about sending electricity through wires. Copper is a common form of wiring as it is relatively cheap, can be easily stretched into wires and has low resistance. The older tungsten light bulbs rely on passing electricity through wires and then across a tungsten filament which produces light. A cold filament has much less resistance than a hot one. That means when you first switch the light on it is able to draw 10 times the current for a very short time before the filament heats up with the result of your light turning on very quickly.
Fluorescent light bulbs however use plasma to produce light and it is here that the calculating genius of Ohm's law falls dead. Plasma is neither a solid or a gas and has a VERY low fluctuating resistance to electricity. Yes fluctuating ... the resistance through plasma is not fixed as it is in wires R=V/I but instead is proportional to the current. The greater the current the less resistance. Huh? That makes no sense and defies the known laws of electricity! That fault cannot be blamed on Ohms law which did not name itself, but was named so by the peers of its creator. Plasma had not yet been discovered and it's strange properties now produce a more efficient form of light for many homes.
When you switch a fluorescent light on, free ions and electrons begin to move rapidly inside the tube of gas. I think these free ions are always present (even when the light is off) due to natural decay in sunlight. The ions/electrons smash into other compounds in the gas ripping off an electron or two which causes more energy ... and more excited electrons which run around inside smashing into everything and creating more and more current. It is like a chain reaction that speeds itself up and intensifies with each particle collision. At first the light is quite dim but as more collisions take place the energy inside becomes greater and excite the trace amounts of mercury gas also inside the tube that when excited produce the visible light we see. That is why your light gradually increases in brightness.
