gases generally do not conduct electricity then why does it conducts electricity in gas filled tube lights?

Asked by Gaurav Avhad | 25th Apr, 2011, 05:53: PM

Expert Answer:

In gas filled tube lights the main procedure is that they apply a large potential differences across a gas column at very low pressure.As the pressure is further decreases in 3-4 mm of mercury,the positive column decreases in length.It starts from anode but ends well before the cathode. A bluish glow is seen around the cathode and there is a dark space between this glow and the positive column.The glow around the cathoe is called cathode glowor negative glow.The dark space between thecathode glow or posiive column is called Faraday dark space.
When the pressure is redued to about 1mm mercury, the positive column is further shortened and the length of the fraday dark space increases.The cathode glow is detached from the cathode and a new dark space, called Crookes dark space appears between the cathode and the cathode glow.
At about 0.1mm of mercuey,the positive column is split into alternate bright and dark bands called tirations.
With further reduction in pressure, the stirations move towards the anode and finally vanish.The cathode glows also vanishes ataround 0.01mm of mercury and the Crookes dark space fills the entire tube..A new phenomenon starts at this stage .The walls of the tube begin to glow and this is called florescence.The colour of the glow depends on nature of the glass.

Answered by  | 1st May, 2011, 12:49: AM

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