Manual

-120-
T
he circuit in this experiment allows you to hear
alternating current. You probably know that the
electric power running through your home is an
a
lternating current. All your appliances that receive
power from electric outlets operate on AC- including
lamps. Lamps actually flicker at the rate of 60 times
per second, but it looks constant because our eyes
see after images. In this experiment you will hear
sound converted from light.
Ready to start? After constructing this circuit, turn
on the power to your kit by setting the switch to A.
Place the CdS cell near an electric lamp. Do you
hear a hissing sound coming from the earphone?
This is the sound of the alternating current. Now
place the CdS cell under a fluorescent lamp, and
listen for a similar sound.
This circuit greatly intensifies the signals of light on
the CdS cell through the operational amplifier.
Adjust the quantity of light on the CdS cell with your
hand. You can probably hear the volume of the
hissing sound reduce and the quality of the sound
improve. See what occurs when you expose the
CdS to sunlight.
N
otes:
EXPERIMENT #100: LISTEN TO ALTERNATING CURRENT
Schematic
Wiring Sequence:
o 15-88-113
o 87-63-131
o 76-93-68
o 70-121
o 69-90
o 75-99-114
o 122-132
o 67-94-81-13-EARPHONE
o 124-119-16-100-89-82-14-EARPHONE
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