also be clearly seen. One metal plate is a
thin sheet. This then follows the insulating
layer of a thin, grey disc. The second metal
plate is a silver-plated surface. There is an
electrical attraction between the two metal
surfaces which change when the capacitor is
charged or discharged. This creates a small
movement that generates the noise.
Electrical noises
Piezoelectricity
The Greek word piezo means
pressure, and some materials
such as quartz have a
piezoelectric effect. If you press
on it, an electrical charge is
generated. Conversely, when
an electrical charge is applied,
a deformation occurs as if one
were pressing on the material.
The insulation in your piezo
speaker is ceramic, similar to
porcelain. Once an electrical
voltage is connected, the disc
bends slightly. This creates a
noise.
Open the 8th door and discover a small
piezo speaker with two wires. The
connecting wires are very thin and soft
and must therefore be protected just like
the battery cables. Make two more holes
in the protective foil of the adapter board
and guide the wires through from below.
Then feed them through the holes provided,
where they should stay until the last
experiment.
In this circuit, there is also a push switch,
and once again a small red and green light
will flash each time the switch is activated.
You will also now hear a soft but clear click
from the speaker each time. However, the
click of the snap-in switch may drown out
the speaker. Use a metal wire or object to
connect the two terminals of the button to
make the click quieter.
The comparison with the previous
experiment has already proven that the
piezo speaker functions like a capacitor.
And indeed, the structure of a capacitor can
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