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4. Lamps
 | Lamps are devices for obtaining light
from electricity.
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| Lamps can be classified into 3 main
categories namely: incandescent-filament lamp, gaseous discharge lamp, and mercury
blended-light lamp.
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(a) Incandescent-Filament Lamps (Figure
5)
Light is produced by means of a filament of carbon,
tungsten, or other metals, heated by an electric current
Figure 5 Incandescent Lamp
(i) Higher Efficacy : the luminous
efficacy is the ratio of the luminous flux emitted from the lamp to the power consumed,
the unit being lumen/watt.
(ii) Longer Life : the filament in an
incandescent lamp evaporates as it is heated
| Incandescent-filament lamps can
be further divided into two types, according to the atmosphere inside the bulb:
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(i) General Lighting Service(GLS) Lamps
ii) Halogen (TH) Lamps
(b) Gaseous Discharge Lamps
These include high/low pressure
mercury vapour lamps, high/low pressure sodium lamps, and mercury halide lamps.
(i) Low Pressure Mercury Vapour (Fluorescent)
Lamps
(ii) High Pressure Mercury Lamps (MBF) (Figure
6)
Figure 6 High Pressure Mercury Lamps
(iii) Low Pressure Sodium Lamp (SOX)
(iv) High Pressure Sodium Lamps (SON, SON-L,
SON-R)
(v) Mercury Halide Lamps (MBI)
(c) Mercury Blended-Light Lamps
Figure 7 Summary of Lamp Types &
their Characteristics
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