Tubelight

a short overview on technicality of tubelight

1. FLUORESCENT TUBELIGHT

2. COMPONENTS OF TUBELIGHT Fluorescent tube’s components Mercury-inert gas mixture Phosphor Coating Electrode coils Mounting assemblies Aluminum cap Electromagnetic Ballast / Choke coil Starter Capacitor Glow bulb

3. CIRCUIT DIAGRAM OF TUBELIGHT

4. Fluorescent tube’s components

5. ELECTROMAGNETIC BALLAST Does the most important work of providing additional voltage for the start of discharge phenomenon in fluorescent tube.

6. STARTER Consist of glow bulb which helps in bringing sudden change in current of circuit. Capacitor helps to avoid electromagnetic interference phenomenon.

7. PHYSICS RELATED In tube light major 3 processes takes place and they are as follows:- THERMOIONIC- EMISSION DISCHARGE OF GAS CONVERSION OF UV RADIATION TO VISIBLE RADIATION

8. THERMOIONIC EMISSION A small amount of current through the electrodes filaments heats up the filament coil. As the filament is oxide coated, a sufficient amount of electrons are present on its surface. The electrons acquires the heat energy produced and moves out of metal surface.

9. DISCHARGE OF GAS The basic discharge process always follows 3 steps:- Free electrons are derived from the electrodes, and they get accelerated by the electric field applied. Kinetic energy of free electrons is converted into the excitation energy of gas atoms when collision occurs between electrons and gases atoms. The excitation energy of gas atom gets converted into the radiation.

10. When an electron just gets free to collide a neutral atom 3 cases may arises. They are:- Electron can rebound with an atom losing small amount of it’s energy The atom can be ionized by realizing it’s own electron. The atom can be excited only but no ionization.

11. UV RAYS TO VISIBLE RAYS The UV radiation produced gets incident on phosphor. Phosphor is actually a semiconductor material. Depending on color of light required, efficiency of light to be produced, combination of gas and phosphor are taken.

12. BIMETALLIC STRIP Physics of bimetallic strip deals with thermal expansion. The metal having larger thermal co-efficient have larger thermal expansion. Metals Thermal Co-efficient Iron(pure) 12 Copper 16-16.7

13. INDUCTOR (CHOKE COIL) At time t=0, as switch is closed resistor is sort circuited. And current flowing through is “I”. At time t=t, when switch is opened, suddenly current flowing through is decreased to zero. Here, as dt tends to zero, V tends to infinity. As a result for that instant inductor becomes a huge voltage source.

14. WORKING OF TUBELIGHT When we switch on the supply voltage comes across the lamp as well as across starter. At the full voltage first the glow discharge is established in the starter because the electrodes gap in glow bulb of starter is much lesser than that of fluorescent lamp.

15. Then gas inside the starter gets ionized due to this voltage and heats the bimetallic strip. That causes to bend the bimetallic strip. Due to it current starts flowing in the glow bulb ; and fluorescent tube gets short circuited. As a result ionization of gas stops, so temperature decreases. So bimetallic strip cools down; as a result contact breaks. As explained earlier, at that instant, a large voltage surge comes across the inductor and gets added with supply voltage. The high value surge voltage comes across the lamp electrodes and strikes the gaseous mixture ; but it will depend on difference in current whether the discharge of gas will occur or not.

16. This process repeats many times within fraction of seconds unit the discharge of gas takes place. When discharge takes place finally the roll of phosphor comes and as explained earlier visible radiations are produced. Starter gets inactive during glowing of fluorescent lamp as it is short circuited.

17. MARKET

18. LIFE SPAN

19. CONCLUSION

20. THANK YOU PRESENTED BY:- AADITYA MEHTA ROLL NO :- 109057 DIVISION :- 9 GUIDED BY:- S.C.ATREE