Elenco LIGHT - Manual (Page 68)

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Method A (easy): Spread some water on the
table into puddles of different shapes, perhaps
like the ones shown here. Touch the jumper
wires to points at the ends of the puddles.
Method B (challenging): Use a SHARP pencil (No. 2 lead is best)
and draw shapes, such as the ones here. Draw them on a hard, flat
surface. Press hard and fill in several times until you have a thick,
even layer of pencil lead. Touch the jumper wires to points at the ends
of the drawings. You may get better electrical contact if you wet the
metal with a few drops of water. Wash your hands when finished.
Method C (adult supervision and permission required): Use
some double-sided pencils if available, or VERY CAREFULLY break
a pencil in half. Touch the jumper wires to the black core of the pencil
at both ends.
Project 145 Musical Shapes
Long, narrow shapes have more
resistance than short, wide ones.
The black core of pencils is
graphite, the same material used
in the resistors in the pivot stand.
Build the circuit and turn on
the switch (S1). Make your
parts using either the water
puddles method (A), the
drawn parts method (B), or
the pencil parts method (C).
Touch the metal in the
jumper wires to your parts
and read the current.
Use the preceding circuit but touch the metal in
the jumper wires snaps with your fingers. Wet
your fingers for best results. Your fingers will
change the sound, because your body resistance
is less than the 100k
Ω resistor (R5) in the circuit.
Next, place the loose ends of the jumper wires in
a cup of water, make sure the metal parts aren’t
touching each other. The water should change
the sound.
Now add salt to the water and stir to dissolve it.
The sound should have higher pitch now, since
salt water has less resistance than plain water.
Don’t drink any water used here.
Project 146
Human & Liquid
Sounds
Build the circuit and turn on the switch (S1).
Touch the metal in the jumper wire snaps with
your fingers. Use the lever on the adjustable
resistor (RV) to adjust the sensitivity of the
circuit. You may see a difference in the light
brightness just by pressing the contacts harder
with your fingers.
Next, place the loose ends of the jumper wires
in a cup of water, make sure the metal parts
aren’t touching each other. The water should
change the light brightness. Readjust sensitivity
using RV.
Now add salt to the water and stir to dissolve it.
The light should be brighter, since salt water has
less resistance than plain water. Readjust
sensitivity using RV.
Don’t drink any water used here.
Project 147 Human & Liquid Light