What advantages does the ordinary fluorescent lamp have over the incandescent lamp?
Higher efficiency
How is visible light obtained in the fluorescent lamp?
In two stages: electrons collide with mercury atoms to produce UV light, then the phosphor coating shifts the wavelength into visible light
What two purposes does the ballast in a fluorescent fixture serve?
To produce the high striking voltage necessary to create an arc, then to limit the current once the arc is established
Fluorescent fixtures are classified according to their methods of starting. Name the three classes
Pre-heat, instant-start, and rapid-start
How does frequent switching of and off affect a fluorescent lamp?
Shortens lamp life
Fluorescent lamps come in three common base types. What are they?
Double-pin, single-pin, and recessed double-contact
What do the letters “HO” and “SHO” refer to in connection with fluorescent lamp identification?
High-output, super-high-output
List 2 methods for reducing the stroboscopic effect in fluorescent lighting circuits?
Lead-lag ballasts, connect to different phases of a three-phases system, or use a steady light source such as an incandescent or LED lamp
Of the three types of fluorescent fixtures, which ballast puts out the highest starting or striking voltage?
Instant-start
What is the main purpose of a capacitor used in rapid-start fluorescent lamp fixtures?
To help provide striking voltage to the lamp
A ballast used for a 2-lamp fixture containing 4ft lamps is also suitable for use in a 2-lamp 8ft fixture. True or false?
False. The 8ft lamps would likely require a higher striking voltage
Blackening of the ends of a fluorescent lamp is ordinarily a sign of what?
The lamp is nearing the end of it’s useful life
What role do the phosphors on the inside of fluorescent tubes serve?
Convert ultraviolet energy into visible energy
Phosphors are used to produce light of different colours. True or false?
True
The brightness of fluorescent lamps as compared to incandescent lamps of the same wattage is ________
Considerably higher
The total heat energy supplied by a fluorescent tube is lower than the heat energy from an incandescent lamp of the same wattage. True or false?
True
The open circuit voltage in a fluorescent tube is about the same as a normal load voltage across the tube. True or false?
False
Briefly explain why a mercury lamp takes some time to reach full brightness
The initial small striking arc is across the base of the arc tube, which slowly raises the pressure and temperature so that the main arc can establish itself
If the outer glass bulb in a mercury lamp breaks, the lamp may continue to operate for some time. Why would it not be advisable to allow operation of the lamp in this condition?
This may allow dangerous levels of UV radiation to escape from the arc tube
What would be the predominant colours of a clear mercury lamp without corrective phosphor coating on the outer bulb?
Blue-ish white
The average warm-up time (to reach full brightness) for a mercury vapor lamp would be ________
5-7 minutes
State two advantages that the mercury lamp has compared to the fluorescent and incandescent
Longer lasting than the fluorescent, and more efficient than the incandescent
State two disadvantages that the mercury lamp has compared to the fluorescent and incandescent
Slow strike up time, long re-strike time
What does the code H33GL-400/DX convey?
Mercury, 33 (ballast designation) Globular, 400W, deluxe white
