Thames & Kosmos Electricity and Magnetism 620417, Руководство по эксперименту

Страница: 18 / 68

WHAT’S HAPPENING
Depending on the position of the switch, the
red or the green bulb will light up.
When you activate the switch, one of the
two lights goes out while the other comes
on.
The setup contains two circuits — one
with the red (figure 1) and the other with
the green light (figure 2). Both are con-
nected at one end to the upper battery
contact. Depending on its setting, the
switch connects first one and then the
other light to the lower battery terminal.
This kind of red-green switch is very use-
ful. If you have a model train set, you
can use it as a railway signal. Or you
can use it as a signal to tell visitors
whether they are allowed to enter your
room or not.
Choice between red
and green
You have probably been asking yourself
what you can use the switch’s third termi-
nal for. Now you’ll find out.
HERE’S HOW
Try the illustrated circuit. Turn on the
switch — what do you see?
EXPERIMENT 13
16
1
2