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EXPERIMENT 14
Electricity
WHAT’S HAPPENING
In the first circuit, the current
runs either to the green light or
to the second switch, which
switches it between the red and
the yellow lights.
In the second circuit, the two
two-way switches and the
push button are each connect-
ed to one of the lights.
17
Your own traffic
light
Of course, red and green are also the
colors that traffic signals use to tell
drivers or pedestrians whether they are
allowed to proceed through an inter-
section or cross the street. Traffic lights
also use the color yellow. Would you
like to be able to control three differ-
ent lights?
HERE’S HOW
Assemble the circuit exactly as shown
in figure 1. If you do it right, you can
choose whether to have the green, red,
or yellow bulb light up. Trace the
course of the current with your finger.
In the traffic lights used in some coun-
tries, the yellow light can shine at the
same time as the red one, or at the
same time as the green one. This setup
can’t do that, but the one shown in fig-
ure 2 can. In this one, the first switch
provides current to the green light,
while the other one controls the red
light, and you can use the push button
to switch on the yellow light whenever
you want.
1
2
Summary of Contents for Electricity and Magnetism 620417
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