Potato Battery

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SCIENCE EXPERIMENTS ON FILE ™? Revised Edition5.40-1 Potato Battery
Lois Fruen and Chelen Johnson

Topic
Construction of a battery

Time
45 minutes to 1 hour

Safety
! Please click on the safety icon to view the safety precautions. Adult supervision is necessary for the soldering of the alligator clips to the wire and when taking apart the battery. Dispose of the potatoes after the experiment; do not eat them.

Materials

12 fresh baking potatoes
24 alligator clips
1.5 m copper bell wire
12 hot-galvanized (not electro-
galvanized) 11⁄? 2-in. zinc roofing nails 12 solid-brass wood screws wire cutters
solder, flux, and soldering iron

Procedure
PART A

one high-brightness red LED
(SLA-591LT3; available at
Radio Shack # 276-006A)
hammer (optional)
voltmeter (optional)
6- or 9-V battery
screwdriver

1. Using the wire cutters, cut 12 pieces of copper wire 10 cm long. Remove 1 cm
from both ends of each piece of wire.
2. Have an adult solder the alligator clips to the wire pieces, one clip to each end. 3. Place one brass screw and one zinc nail 1⁄? 2 in. apart in each potato. Use the
hammer if you find it easier, but be careful not to crush the potatoes. Make sure
that the nail and screw don’?t touch inside or outside the potato. Leave the heads
of the screws and nails approximately 1 cm above the potato (see figure 1). 4. Connect an alligator clip to the nailhead. Connect another clip from a different
wire to the screwhead.
5. Attach the LED between the two clips left unconnected. Observe what happens.
Turn the LED around so that the opposite lead is in the opposite clip. Observe
what happens. Use the voltmeter to take a reading.

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5.40-2SCIENCE EXPERIMENTS ON FILE™? Revised Edition

Figure 1

1 cm

6. Connect each potato to every other potato by using a wire to connect a nail to
the next potato’?s screw (see figure 2).

Figure 2

7. When all the potatoes are connected, there should be two clips left over, one
coming from a screw and one coming from a nail. Attach the LED between the
two leftover clips. Observe what happens. Reverse the leads of the LED. Ob-
serve what happens. Use the voltmeter to take a reading. (If there is no result,
make sure that every connection is from a zinc nail to a brass screw). 8. Remove the potatoes one at a time, and connect the LED to the new free clips
each time until it no longer lights. Take a voltage reading with the voltmeter.
Observe any differences in the intensity of the LED’?s glow. PART B
1. Have an adult help you to take apart the 6- or 9-V battery. Be careful not to cut
yourself on sharp metal edges.
2. Try to identify the parts that you observe, and compare them with the potato
battery that you constructed in Part A.
3. Why do you think the individual cells (potatoes) are connected to each other in
the order that they are?
4. Which parts of the battery you took apart correspond to which parts of the
potato battery...
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