Flickering aside, fluorescent lights are efficient
Flickering, non-functioning fluorescent light tubes can be annoying. Whether one is in an indoor sport area, at work or at home, most of us have witnessed this malfunctioning flicker.
Fluorescent light bulbs either flicker as if to try (unsuccessfully) to start long after one has turned on the electrical switch or else only glow miserably at each end, with no useful light emission. Either way, they clearly need attention. Although nothing worse usually happens, it is not recommended to leave a flickering tube too long.
A service person can usually resolve the problem by inserting a new starter (tens of cents worth!) into the side of the light housing, or replacing the fluorescent tube, or both.
Today, most popular fluorescent lamp design incorporates a rapid start lamp system which employs a ‘‘ballast’’. Older lights use a starter switch.
However, irrespective of the starting mechanism employed, a useful, bright and constant light is produced by an electrical current conducted through an excited or ionised mercury vapour inside the lamp (for white light).
Other gases are ionised inside coloured ‘‘neon’’ lights. The process involved is called a gas discharge process. The gas discharge process, if not carefully controlled, could become explosive if a constant current is not maintained.
Since a fluorescent light does not instantly switch on, the current flow is not constant during the switching process, changing very rapidly.
The older heater-type starters relied on two electrodes at each end of the tube being wired in such a way as to create a charge imbalance between the two ends of the tubes.
When the electrodes quickly heat up in the initial start process, electrons start to boil off the electrodes, moving into the gas inside the tube. This causes excitation of the gas. The excited gas then starts to conduct electrical current and gives out light.
In the ‘‘instant start’’ (different from rapid start) modern day devices, a very high voltage is applied very quickly.
This causes an excess of surface, or free electrons (called a corona discharge) to move into the gas, causing a similar excitation process of the filler gas to follow.
Unlike in solid electrical conductors, where current resistance is constant at constant temperature, the gas resistance in a fluorescent tube decreases as more gas ionises. This causes more gas to ionise, further decreasing resistance to current flow, leading to a potentially explosive process.
In both lighting systems, if the current were uncontrolled and allowed to rise continually, the lights would explode.
In older lighting systems, a magnetic induction system was used to control the changing current as the gas ionised, preventing a runaway current increase. These fluorescent lights used to hum and flicker noticeably, even when functioning properly, because the rate at which the magnetic inductors could react to current changes was at an audible and visible frequency.
Modern lighting systems use more sophisticated electronic control systems which cycle at very high frequencies, using inductor coil loops coupled with more electronic circuitry.
These systems are more efficient and reduce the risk of photosensitive eplilepsy from low frequency light flicker.
Whichever system one has, the starter generally needs replacing if the light does not initially flicker when switching on the light. If the tube can be seen to try to start with a visible flicker at the ends, then it is likely to need replacing.
In general, fluorescent tubes last a lot longer than incandescent lights. They may be annoying when malfunctioning, but they are hard to beat for efficient lighting solutions.