2. Construction, working and Applications of
Following Lamps:
- Incandescent Lamps.
- Fluorescent Tube
- Compact Fluorescent Lamps (C.F.L.)
- LED Lamps.
4. .
Filament lamps must have,
1. It should have high melting point (3500º C).
2. It should have high resistivity.
3. It should have low temperature co-efficient.
4. It should have low vapor pressure.
5. Mechanically Strong, ductile.
Material used for filament is Carbon, Osmium tantalum and
Tungsten.
Gas used inside the lamp ( Nitrogen orArgon )
Life: 1000 Hrs working hrs. Lamp efficiency: 10 - 30 lumens/watt
5. Working:
Lamp work on the principal of Incandescence
( i.e. when a hot body is heated, radiant energy is emitted in waveform).
□ An incandescent bulb generates light through heat.(95% Heat,5% Light)
□ When electrical current passes through the tungsten filament, it
heats to the point where it glows and gives off a yellow-red light.
□ To keep the filament from burning up immediately, it's housed in a
vacuum. Even so, the intense heat of the filament ensures a
comparatively short and expensive life span.(Working avi)
Applications: Domestic, Commercial and Industrial. Etc…
7. A fluorescent lamp tube is filled with a gas containing low
pressure mercury vapor and argon, xenon, neon, or krypton.
The pressure inside the lamp is around 0.3% of atmospheric
pressure.
The inner surface of the lamp is coated with a fluorescent (and
often slightly phosphorescent) coating made of varying blends of
metallic and rare-earth phosphor salts.
The lamp's electrodes are typically made of coiled tungsten and
usually referred to as cathodes because of their prime function of
emitting electrons. For this, they are coated with a mixture of
barium, strontium and calcium oxides chosen to have a low
thermionic emission temperature.
9. Working:
Cathode filament emitting electrons after getting heated due to supply of current .
These electrons while accelerating collide with Argon and Mercury vapour atoms.
The excited atoms of Mercury give a radiation
10. Applications:
1.In US residences, fluorescent lamps are mostly found in kitchens,
basements, and garages.
2. In countries, like India…
i) Residential.
ii) Commercial.
iii) Small scale industries ….Etc.
12. COMPARISION WITH INCANDESCENT LAMPS:
Incandescent CFL
1) Life Span: 1000 Hrs 6000-15,000 Hrs
2) Energy consumption: More Less
3) Cost : Less More
4) Starting time: Immediately Take time to give
full illumination.
13. 8. LED ( Light Emitting Diode) Lamps:
LEDs are semiconductor devices
that produces light when an
electrical current applied to them.
Latest Lighting Technology.
Invented in 1962.
Lower energy consumption.
Longer life : 50,000 – 100,000 Hrs.
Smaller size , Faster switching.
Dimming.
