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Why old tube flashes three-four times?

Date: 10 Feb 2012   Group: Science and Technology    Category: Science   


Why an old tube flashes three-four times when it is switched on? I used to think this often why it flashes although there is passage of current through it? But why not a bulb or other electrical devices do this kind of flashing? Please answer if you do know.


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Author: [Anonymous]    15 Feb 2012      Member Level: Bronze     Points : 3    Voting Score: 0

In tube lights mercury vapour is present. When electricity passes between the two ends, the mercury vapour inside the tube light excites and it produces short ultra violet waves. This waves when touch to flourscene on the tube light, a visible light is produced. After some days due to current, the flourscene layer gets completed at the edges of the tube light and it take sometime to glow fully. This ultraviolet rays supplies slowly to the edges and it take 2 to 5 seconds to glow full. We can observe that when a two tube lights are taken in which one is old and other is new, then new bulb glows brighter than the old one because in the older one the flourscene layer will be depleted.
Author: venkaiahreddy kota    15 Feb 2012      Member Level: Bronze     Points : 3  (Rs 2)    Voting Score: 0

In tube lights mercury vapour is present. When electricity passes between the two ends, the mercury vapour inside the tube light excites and it produces short ultra violet waves. This waves when touch to flourscene on the tube light, a visible light is produced. After some days due to current, the flourscene layer gets completed at the edges of the tube light and it take sometime to glow fully. This ultraviolet rays supplies slowly to the edges and it take 2 to 5 seconds to glow full. We can observe that when a two tube lights are taken in which one is old and other is new, then new bulb glows brighter than the old one because in the older one the flourscene layer will be depleted.



Author: naveen kumar polakala    17 Feb 2012      Member Level: Silver     Points : 5  (Rs 3)    Voting Score: 0

we know that in general bulbs, tungsten filament is heated by passing electric charge and that heat energy is converted in to light energy which is visible light.You can even feel the warmth when you touch a bulb even after it is switched off.
In a tube light there is no such filament but the entire tube is filled with mercury vapour, when electric charge is passed through it, due it diffraction of waves UV light is generated throughout the tube which is invisible to human eye, but due to the fluroscent coating on the walls of the tube the UV light generated comes out as a visible light.
For exciting the mercury vapour large amounts of electric charge is required that is the reason why a starter and electric choke are used. It takes some time for complete excitation of mercury vapour in some 3-5 secnds, we can observe this in terms of flashes, once the vapour is excited, starter cuts off the choke and now less electric charge is required for its operation. So if you frequently turn off and turn on the switch of tube light or if the tube becomes old it takes more time for it to be turned on this problem can be attributed to the integrated problems of starter, choke, vapour and fluroscent coating.
When compared normal bulb, tube light is more energy efficient in long run.

Author: Ramprasad    23 Feb 2012      Member Level: Diamond     Points : 5  (Rs 3)    Voting Score: 0

Hi,
In normal electric bulbs, light transfers due to the heating of filament. However, in tube-light we cannot find the same. In the lengthy tube shaped lights, mercury vapour will fill. These vapour cells ionizes with the inspiration of electric-power. Light will produced due to the rays that have generated at that time. Theses rays are ultra violet rays, which are not visible by eyes. These rays reflect on the phosphorous-coated inner walls of the tube-light and convert as visible light. For the ionization of vapour, high electric voltage needed, which supplies through tube light starter and choke. Once ionized then less voltage is sufficient. Hence, starter cuts-off choke. We have the habit of switch on and switch offing the tube-light regularly which needs high voltage supply always. It interrupts the process of ionization of vapour, which reduces the lifetime of tube-light. Due to always switching on and switching off the tube-light it starts to flash three to four times regularly. The flashing of the tube light indicates that the lifetime of the tube light is coming to an end, we have to replace it. Therefore, we people have to avoid the habit of switching on and switching off the tube-light unnecessarily in order to increase the life of the tube-light.


Author: shashi    08 Mar 2012      Member Level: Silver     Points : 2  (Rs 2)    Voting Score: 0

1. As we know in tube light, mercury vapour will react against the electricity what ever we apply .
2. And the light is emitted by the spark generated in reaction of mercury vapour and electron.
3. the light produce during the sparking is unvisual by eye that it is ultraviolet rays are generated.
4. these ultraviolet rays attack on phosphorous-coted inner wall of the glass and converted as visua llight.

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