## 1000 Science Fair Projects with Complete Instructions

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POTATO POWER

Purpose:

In this activity, you will learn how to build a battery from potatoes.

Materials:

metal strips: copper, aluminum, zinc (galvanized steel)
potatoes (at least 4)
multimeter (volts, milliamps)
wire clips
steel wool (to clean the metal strips)

Procedure:

1) Select two different metal strips and one potato.
2) Carefully place the metal strips into the potato.
3) Voltage: Set the meter to "DC Volts" and make sure the probes are plugged
into the correct jacks. Also make sure that the scale is correct. All
multimeters are different, but there should be a low scale, something like 2V,
or 6V.
4) Attach wires from the meter's probes to the metal strips.
5) What does the meter read?
6) Current: Set the meter to "DC milliamps" and make sure the probes are plugged
into the correct jacks. (Use the smallest setting on the multimeter.)
7) Attach wires from the meter's probes to the metal strips.
8) What does the meter read? (enter on the worksheet) (You may notice that the
current decreases. As the current decreases, you are draining the battery. So
take your measurement, then disconnect the wires.)

1) Different metals: Now that you know how to make a potato battery, and know
what voltage and current are, you will try to make a better battery.
Some metals make better batteries than others. You will try to find the
combination of metals that gives the most voltage and current.
What combination of metals made the most voltage and current together?

2) Potatoes in Series
Make another potato battery.
Wire up the two potatoes in series.

3) Light the LEDs
Now you are qualified to be a battery engineer! Your job is to design a more
complicated potato battery to light two LEDs.
Two LEDs need 1.6 volts and 1 milliamp to light brightly. The more current, the
brighter the light. By putting potatoes in series and parallel, design a battery
to do this:
Now test your battery with the LEDs. LEDs are special lights that have a
positive side (red wire) and negative side (black wire). Make sure you attach
the positive side of your battery to the red wire and the negative side to the
black wire.

Notes
The best combination of metals should be copper and zinc.
The LEDs used here are special low current LEDs, rated for 1.8 V and 1 mA, but
they will fire at about 1.6 V and .2 mA.
One LED should fire with 2 potatoes in series (this barely produces the needed
1.6 V), but you may need 3.
The 2 LED eyes are wired in parallel. Four potatoes should brightly light the
eyes: two pairs in series, those pairs in parallel.
The zinc used here is really galvanized steel, meaning zinc coated steel. Zinc
is dissolved from the strips in the battery, so the metal strips have a finite