1. By: Allison Helton Completed: December 2nd, 2014
Helton’s Science Fair
By: Allison Helton
Completed: December 2nd, 2014

2. Scientific Question
How do you connect & how many potatoes does it take to power a light or a buzzer?

3. Background
I chose this experiment because I wanted to see what it was like using electricity from- POTATOES! I wanted to conduct electricity from other things, not just batteries. Above all, I want us all to have a bright future and have more advanced electricity.

4. Hypothesis
If I use more than one potato, then it will power the LED light or the buzzer.

5. Variables
Independent: number of potatoes and how they are connected in series and parallel
Dependent: amount of voltage and current
Constants: same vegetables, same devices, same battery, same electrodes

6. Procedure Insert the electrodes into the potatoes
Some juice may leak out of the potatoes. Work on a surface that is easy to clean.
Press one copper and zinc electrodes into the middle of the potato, spaced on either end. Press them in until they almost poke out to the other side.
Repeat this for the other two potatoes.
Prepare a data table in your lab book. You will use the table to record the open-circuit voltage and the short-circuit current of your potato batteries and note whether they power the LED light or the buzzer.
Measure the open- circuit voltage and short-circuit current of a single potato battery.
Investigate whether or not a single battery can power an LED or a buzzer.
Test two potatoes in series.
Repeat steps 3 & 4 with two potatoes connected in series. Remember to test open-circuit voltage, short-circuit current, the LED and buzzer.
Test two potatoes in parallel.
Repeat steps 3 & 4 with two potatoes connected in parallel. Record your results.
Test 3 potatoes in series.
Repeat steps 3 & 4 with 3 potatoes connected in series Make sure you enter your results.
Test 3 potatoes in parallel.
Repeat steps 3 & 4 with 3 potatoes connected in parallel. Record your results.
Analyze your data.
Your data table should be completed. Making graphs may help you visualize your data
Make a bar graph of open-circuit voltage vs. # of potatoes. Include data for both series and parallel.
Make a bar graph of short-circuit current vs. # of potatoes. Include data for both series and parallel.
Write your conclusions.
How do voltage and current change in each case?
How much voltage and current does it take to power the LED? Is there a certain voltage and current below which the LED won't light up?
How much voltage and current does it take to power the buzzer? Is there a certain voltage and current below which the buzzer made no sound?

7. Data
Experiment Data Table.

8. Data
Open circuit voltage for potatoes in series and parallel.

9. Data
Short circuit current for potatoes in series and parallel.

10. Conclusion
The scientific question was how do you connect and how many potatoes does it take to power a light or a buzzer. I would connect the potatoes in series and parallel, measure the voltage & current every time that I investigate to see if it would power an LED and a buzzer or not. I used the digital multimeter to measure the voItage from a single potato. I found that 0.97 volts and 0.36 mA powered nothing ( one potato ), and 2.56 volts and 0.25 mA powered both ( 3 potatoes in series ). Below 3 potatoes in parallel or series my LED would not light. I took at least (2.56 volts and 0.25 mA) to light the LED. Below 2 potatoes in series or parallel the buzzer would not work. It took at least (1.84 volts an 0.29 mA) to make the buzzer work. My data supported my hypothesis because I expected one potato to power nothing, and more than one potato to power the light or buzzer. I have learned many things. Including: If the voltage increases, the current decreases. Potatoes in parallel have less voltage, but more current than potatoes in series and potatoes in series have more voltage and less current than potatoes parallel. I also learned the difference between open- circuit and short- circuit. I also learned that when I poke the electrodes through, a chemical reaction happened with the potato juice, creating electricity. When I poked in a electrode for the first time, it poked all the way through. The electrode was hard to poke through, so without being careful, I accidently went through. I would have gotten bigger potatoes so I wouldn’t have poked through so easily. When I put the red positive wire on the zinc and the black common wire on the copper the meter read volts. That meant the wires were backwards and the positive electrode was the copper. To connect potatoes in series I connected the positive to the negative electrodes with wires. To connect potatoes in parallel I connected the negative electrodes together and then the positive electrodes together with wires.