Elenco Deluxe Snap Rover® - Manual (Page 40)

-39-
OBJECTIVE: To show how water conducts electricity.
Project #55
OBJECTIVE: To draw resistors in different shapes.
Write Your Parts
Build the circuit at left and connect the jumper wires to it, but leave the loose
ends of the red and black jumper wires unconnected for now. There is one
more part you need and you are going to draw it. Take a pencil (No. 2 type is
best but other types will also work). SHARPEN IT, and fill in some of the
shapes shown. You will get better results if you place a hard, flat surface
directly beneath this page while you are drawing. Press hard (but don’t rip the
paper), and fill in the shape several times to be sure you have a thick, even
layer of pencil lead.
Turn on the slide switches (S1) and take the loose ends of the jumpers, press
them to one of the shapes and move them around over it. If you don’t hear any
sound then add another layer of pencil lead, or put a drop of water on the
jumper ends to get better contact. Create some shapes of your own and see
how they work.
Use the knobs on the sound & recording IC (U9) and the lower slide switch to
change the sounds.
Shapes to be drawn.
Use a SHARP No. 2 pencil, draw on a
hard surface, press hard and fill in
several times for best results.
This shape can make sounds like a kazoo.
R
O
VER REAR
Project #56
The Sound of Water
Use the preceding circuit but take the loose ends of
the red and black jumper wires and place them in a
cup of water, without letting them touch each other.
The sound changes when both wires are in the
water, so you have a water detector!
Now spread some water on a table in puddles of
different shapes. Touch the jumper wires to points at
the ends of the puddles and compare the sound.
The sound may vary depending upon your local
water supply. Pure water (like distilled water) has
very high resistance, but drinking water has
impurities mixed in that increase electrical
conduction.
OBJECTIVE: To show how adding salt to
water changes water’s electrical characteristics.
Project #57
Salt Pitch Changer
Use the preceding circuit and cup of
water. Slowly add salt to the water and
see how the sound changes, mix it a
little so it dissolves. The pitch
(frequency) of the sound will become
lower as you add more salt. You can
use this circuit as a saltwater detector!
You can then increase the pitch by
adding more water to dilute the salt.
Take another cup of water and try
adding other household substances
like sugar to see if they change the
sound as the salt did.