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Working of Tubelight

Fluorescent lights use electric charge to excite mercury atoms, producing ultraviolet light which causes a phosphor coating to glow white. A starter is used to provide initial current to the filaments, as the voltage is not enough to ionize the gas. The starter contains a small glass tube with neon and a bi-metallic plate. When power is applied, the gas in the starter ionizes and heats the plate, increasing current to the main tube filaments until the gas ionizes and the light turns on. The plate then cools and the starter resets to restart the process when needed.

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776 views2 pages

Working of Tubelight

Fluorescent lights use electric charge to excite mercury atoms, producing ultraviolet light which causes a phosphor coating to glow white. A starter is used to provide initial current to the filaments, as the voltage is not enough to ionize the gas. The starter contains a small glass tube with neon and a bi-metallic plate. When power is applied, the gas in the starter ionizes and heats the plate, increasing current to the main tube filaments until the gas ionizes and the light turns on. The plate then cools and the starter resets to restart the process when needed.

Uploaded by

jsrilakshmi4272
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Fluorescent lights are among the most popular lighting system used worldwide.

worldwide. Fluorescent tubes/lamps are filled with


mercury(or argon, inert) vapor. They use electric charge to excite mercury atoms in order to produce ultra violet light. (This ultra
violet light when incident on phospour powder coated on the glass tube due to which it appears white produces visible light) A
glow starter or commonly known as starter is used in the tube light circuit to provide an initial current to filaments of the tube
light. To understand the purpose exactly why a starter is used in the tube light circuit, lets look into its circuit.


When the switch is pressed current cannot pass through the tube initially because the gas inside it is not ionized and hence the
tube light circuit behaves as open circuit. Once the gas is ionized, it will provide a conduction path for the current to flow. In
order to ionize the gas, an initial high current is required for a short period across the filaments of the main tube. That is what a
starter does. A starter initially provides a path to complete the circuit and once tube light starts the current flows through the
ionized gas in the main tube.


When power is applied to a tube light circuit, this voltage is not sufficient to ionize the gas inside the main tube. However, this
power generates an electric potential across the contacts of small tube of starter. This electric field is large enough to ionize the
gas inside the small tube and hence a current flow in the two contacts through the ionized gas. The heat generated due to the
flow of current expands the bi-metallic plate towards the other plate and within a few tenths of seconds, it touches the other
plate. This serves two functions first, it will de-ionize the gas(this means the starter is open when high voltage is created
across the tube and the main tube ionises) and second, it will increase the current through the filaments of the main
tube.(flashing of tubelight during starting because

Now the gas of the main tube gets ionized and current starts flowing through it. Thus the bi-metallic plate of starter cools down
re-opening the gap between the two contacts. This gap will remain open until the tube light will start next time.
(black strips at the ends of the tube are filaments)
(Starter has a glass tube filled with neon which is energised with the current when sitch is closed(on) and a bimetallic contact)


RFI suppression capacitor has the following functions in the tube light circuit:
a. Absorbs the electric noise created by discharge around the electrodes in order to suppress the radio frequency
interference with other electric devices.
b. Attenuates the initial striking voltage from the ballast and make it wide too in order to ensure more reliable starting
operation.
c. By avoiding arching(short circuit) between glow tube contacts, it ensures a long contact life.

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