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If you turn on a fluorescent tube-lamp, it flickers before lighting up.
If you then turn it off and turn it back on after 2 seconds, this time it doesn't flicker but lights up straight away.
If you wait for some time (say 10 minutes) and switch on the light again, it flickers before lighting-up, again.

Why does it flicker before lighting up?
And why doesn't it after a 2 seconds gap in turning it on and off?

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2 Answers

up vote 3 down vote accepted

There are several types of Fluorescent Lamps which each might have a different ballast circuit. In general, the flicker is caused because the gas inside the lamp is still relatively cold and cannot establish a glow discharge between electrodes. Once the lamp has been heated enough, the gas ionizes and the lamp glows. So if you turn it off for a few seconds and turn it back on, the gas is still relatively hot and ionized, which makes easy to start. When you wait 10 minutes, the lamp is cold, and will be harder to start again, generating a flicker.

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nice answer. however, it is not an "arc" (which is lightning) it is a "glow discharge". –  Andreas H. Feb 2 at 4:12
edited to reflect Andreas H. comment –  CAGT Feb 2 at 4:32
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It doesn "blink" when the fourescent tube is still warm, hence, your observation that it turns immediately on after it was only briefly off.

The blinking occurs because the the starting circuit tries several time to establish a the current flow in the tube. It may not light up instantly because the gas inside needs to reach a certain temperature first.

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