Lamp Caps
The third incandescent lamp variable is the lamp cap. The lamp cap must match the socket in
which the lamp will be used. Most incandescent lamps have bayonet caps in UK and screw caps for
mainland Europe. Originally the different caps helped to separate different supply voltages.
Figure 4.4. Incandescent lamp caps.
Some other types of lamp cap used for incandescent lamps are shown in Figure 4.5.
Figure 4.5. Other lamp caps.
In some cases special lamp caps are used to prevent the wrong type of lamp from being
installed.
Lamp Types
The fundamental difference between lamp types is the way the filament, is coiled and
supported. The tungsten wire is very fine with a diameter less than human hair and the overall
length of 100W filament is nearly 1.2m so coiling is necessary to produce a sensible sized lamp.
Figure 4.6. Single and Coiled Coil detail.
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