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TM 9-8000
Figure 16-2. Lamp Construction and Configuration.
age used in automotive electrical systems is low and the
use and the number of lamps used. All storage batteries
current required as a result is high, the filaments are
are rated by ampere-hours; that is, the number of hours
much shorter and stronger than those used for standard
a battery can be used at a certain discharge amperage
house lighting lamps. A short and thick, rather than a
before it becomes depleted. For instance, two headlight
long and thin, filament can withstand rough treatment,
lamps burning at 4 amperes each, a total of 8 amperes,
and this is desirable in the case of a lamp subjected to
would discharge a storage battery rated at 80 ampere-
the vibrations of a motor vehicle. A short filament also
hours In approximately 10 hours, unless the generator
provides a concentrated light source that will give a
charged the battery.
better focus.
Light Beams(Fig. 16-3).
c.  Size (Fig. 16-2). Lamps range in size from the
small one-half candlepower instrument panel lamps to
a. Use of Reflector. A lamp bulb is mounted within
the large 50 or more candlepower driving lamps.
a reflector so that the light can be gathered and directed
In a confined beam. The best light beam from a lamp is
d. Current Requirements.  The 2-candle power
obtained by the use of a parabolic or bowl-shaped -
lamp consumes 0.21 ampere at 12 volts. The 4-
reflector, which is the type In general use. There is a
candlepower lamp consumes 0.22 ampere at 12 volts. A
focal point near the rear of the parabolic reflector at
lamp similar to the one shown in figure 16-5, having two
which the light rays from the lamp are picked up by the
filaments, one of 32 candlepower and the other of 21
polished surface of the reflector and directed In parallel
candlepower, will draw 1.3 and 1.8 amperes.  One
lines to give a beam with a circular cross section. Any
reason for the rapid discharge of storage batteries in
other position of the lamp will not give as limited a beam,
winter is the increased number of hours that lamps are
but will tend to scatter the light.
used. There is a direct relation between the total current


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