1mA
You can buy a cola-powered clock.
Project 80
Cola Power
Set the meter (M5) to the 1mA scale and
connect the jumper wires to it. Connect the
other ends of the jumper wires to the snap
electrodes (red to copper), and place them
in a cup of cola soda.
Read the current on the meter. You may
switch the meter to the 5V scale to also
measure the voltage produced, but the
voltage may be too small to measure ac-
curately with a simple meter like M5.
Try replacing the cola with other flavors
and compare them.
Throw away the soda used in this project.
Wash off the electrodes.
Cola-flavored soda is lightly
acidic.The acid is similar to
the material used in some
types of batteries, though
not nearly as strong.
The acid in the cola will
react with the copper and
zinc electrodes to make an
electric current, just like the
AA batteries or the larger
battery in your family car. As
some of the acid in the soda
is neutralized, the current
produced drops.
Project 81
Fruit Power
1mA
Squish or roll a lemon a few times to break up some of the cells inside
(tomatoes or grapefruit also work). Stick the copper and zinc snap elec-
trodes into the lemon. Set the meter (M5) to the 1mA scale and connect
the jumper wires to it, then connect the other ends of the jumper wires to
the snap electrodes (red to copper).
Read the current from your “lemon battery” on the meter. Try placing
the electrodes in different parts of the lemon to see how the current
changes. You may switch the meter to the 5V scale to also measure
the voltage produced, but the voltage may be too small to measure ac-
curately with a simple meter like M5. You may see the current/voltage
slowly drop as the “lemon battery” is used up.
If you don’t measure any current, move the electrodes closer together
or to a different place on the fruit.
Replace the lemon with other fruits or vegetables such as a tomato,
grapefruit, orange, carrot, or onion; see how much current they produce.
Throw away the fruits and vegetables when you are finished with this
project. Wash off the electrodes.
-68-
Some fruits and vegetables have a sour taste
because they are lightly acidic. The acid in
them is similar to the material used in some
types of batteries, though not nearly as strong.
The acid in the fruit will react with the copper
and zinc electrodes to make an electric cur-
rent. As some of the acid in the fruit is neu-
tralized, the current produced drops.
SC_STEM1_manual_PRINT.qxp_Layout 1 7/13/17 4:45 PM Page 69