The purpose of the choke is to provide a very high voltage initially between the filaments (across the two ends of the tube light). Again once the gas in the tube is ionized the choke provides a low voltage. A choke is a coil of wire.
Fluorescent tubes/lamps are filled with mercury vapor. They use electric charge to excite mercury atoms in order to produce ultra violet 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.
The function of choke is to provide high voltage enough for ionization to take place in a tube light and after establishment and substenance of ionization, limit the voltage across the tube. That is the reason why a tube fuses when the choke is shorted.
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Gases present in the tube light is of such nature that once the gas ionised then it has a tendency to increase continuously accompanied by a fall in the circuit resistance . in order to limit the current to a safe value choke is used .
choke performs two function
1) providing ignition voltage
2) limiting the current
Choke is nothing but a Transformer. To limit the current in the circuit and to increase the force(Voltage) it is used.
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Now observe below figure
There will be two terminals at both the ends of tube in which two terminals are connected to the starter/thermocouple. And two will serve as phase and neutral.
Choke is connected in series with phase as the tube as hallow space immediately after supply is switched on the electrons won’t flow through the hallow space, so Choke is used to increase voltage to free electrons in the hallow space. It also serves for below purposes.
1.Fuorescent lamp is supplied with constant voltage, which it causes high current in to the hot electrode. Due to high current electrode may get damage. So to minimize the current Choke is used.
2. By minimizing current voltage increases, So the mercury vapour and organ in the hallow space bombard each other and electrons will move freely from one end to another.