Question

What is the need for fluorescent material?

Answer 1

First of all to understand about use of choke lets concentrate on how does a fluorescent lamp actually works. The lamp we are disscusing is a premitive kind of lamp which is said to be preheat fluorescent lampHave a look at this circuit, We apply ac voltage at point B and by going through ballast it goes to lamp and we also have a starter switch in the circuit. So lets start from beginning how we start a lamp
1. We switch on the AC supply
2. Now the power is passed through the ballast which is an inductor and it basic function is to limit current and avoid making a short circuit in the lamp. We will discuss the details later.
3. Now the current passes through the filaments and thus heating the filaments and also the gases present there, The discharge tube is filled with argon gas and have a phosphorus coating inside it and it also have a small amount of mercury in it.
4. Then the current goes to the starter now lets see whats inside a starter we have a neon lamp and a bimetallic strip what happens in the starter is that the current flows through the neon or argon lamp and this heats up the bi metallic strip.
5. Now when the bimetallic strip is heated by the lamp then the due to its characteristic the strip expands and completes the circuit thus bypassing the lamp and creating a short circuit.
6. When the circuit is short the voltage drops to zero and when the bimetallic strip cools down it pops back to original position thus opening the circuit, now here the ballast comes into the picture as the ballast has a inductor in it and it has its own magnetic field thus when the circuit is cut down it causes magnetic field to collapse and this creates a "Inductive kick" which is nothing but a surge of high voltage this high voltage goes through the filament and produces arc as they the filament and argon gas around it was preheated.
7. This arc causes the argon gas to excite and leave photon this emission of photon causes emission of UV light which when goes through the phosphorus coating inside