Purpose: Which fruit/vegetable will produce the most electric voltage?

Hypothesis: When I attach a galvanized nail and copper strip to a potato, the greatest voltage will be produced.

Materials: Fruit/vegetable, Voltmeter, 2 wires, 2 different metals (copper/zinc), knife

Procedure: 

1. Cut the piece of fruit/vegetable
2. Put it in 2 pieces of metal
3. Attach the voltmeter using wires
4. Record the results
5. Compare results from several pieces of fruit

Why? The potato will produce the greatest voltage because it has electrolytes on its surface. Electrolytes act as an electrical conductor and allow the flow of electric charges. When metals like zinc and copper are inserted into the potato it will produce the highest voltage.

Observations:

• We played around with the each of the fruits and vegetables and tried out different set ups. First, we inserted the galvanized nail and copper strip completely into the fruit/vegetable. The voltage didn’t fluctuate of change. We did this the other way around and only stuck the nail and copper strip on the the skin of the fruit/vegetable. The voltage remained the same even though both metals weren’t inside the fruit.
• We also tried different things with the voltage wire. When we attached the red wire to the nail the voltage went into the negative. When we attached the same wire to the copper strip, the voltage numbers were positive.
• We also made the nail and copper strip touch each other in the experiment. This gave an interesting result as the voltage numbers kept changing as. We tried this out on the apple and the discovering that was pretty cool.
• We also tried another experiment where we had to make a led light up using fruits, galvanized nail and copper strips. It took us a long time but we finally figured out that we had to make a circuit. The circuit had to be connected in a pattern in order for the led to light up.

Results:

1. Lemon: 0.3 volts
2. Pear: 0.5 volts
3. Potato: 0.45 volts
4. Apple: 0.4 volts
5. Mandarin: 0.4 volts
6. Pickle: 0.85 volts
7. Cherry Tomato: 0.5 volts

What is causing electrons to flow in this experiment?

The electricity isn’t coming form the fruit/vegetable. Instead, it’s coming from a chemical reaction resulting from the differences in electro-negativity between zinc and copper. Like a waterfall, this cause the electrons to move from a high potential region to a low potential region. Since the nail is made of zinc which is more reactive than copper.

What are the independent, dependent and controlled variables of this experiment?

Independent: Fruits and vegetables

Dependent: Voltage

Controlled: Galvanized Nail and Copper Strip

How can we modify our experiment to improve our results?

• • Usage of fresh fruit and materials: A few of the fruits were a couple days old. To make the experiment as accurate as possible, having fresh fruits that are contaminated or rotten is important. The nail and copper should not be corroded. This could have been a source of uncertainty for the experiment.
  • Sizing: Having larger fruits, nails and copper strips can lead to more accuracy. This will increase chances of a reaction and more accurate results. A lot of fruits were small and breaking apart. For a few of them the nail and copper strip weren’t even able to stand up. This could have interfered with the results.
  • Repetition: In all our previous labs we made sure to perform the experiment atleast 2-3 times and taking the average of the results. We only did the experiment once on each fruit. Only doing it once doesn’t always give accurate results.

What could be sources of error or uncertainty in our experiment?

• Contamination: The fruit could be improperly washed causing dirt particles to interfere in the experimentation process.
• Temperature: The temperature of the fruit could be fluctuating throughout the experiment. Chemical reactions can be affected by this.
• Human Error: Misreading the voltmeter or placing the galvanized nail and copper strip improperly could mess with the results. Sometimes I got confused while reading the voltmeter and my partners made sure to correct me to get accurate results.

How can I use this in my everyday life?

• Mr. Robinson gave us a challenge to use fruits, galvanized nails and copper strips to make a mini bulb light up. It took us several tries but we figured out that it takes a full circuit for the bulb to light up. I found this very intriguing and realized I could apply what I learnt in this experiment to real life situation. For example, creating my own light only using a couple materials.
• After some research I read that some of the materials we used can be used for many purposes. For example, a galvanized nail is coated with zinc to prevent rusting Not only that, copper strips are used for metal detection.
• You can also check the acidity of a fruit using a galvanized nail and a copper strip.

Conclusion:

My hypothesis was incorrect. I predicted that the potato would have the highest voltage due to the electrolytes on its surface. I was proved wrong after doing the experiment and the pickle had the highest voltage. Just like potatoes, pickles are also great conductors of electricity due to their high salt content. After learning that, the results make a lot more sense. After the experiment I wonder what would have happened if I used a large pickle. When we used the pickle, there were already several holes in it and it was mushy. Even though it wasn’t in proper form it still had the highest voltage. I wonder what would have happened if I used a fresh pickle that was big and unused. How much would that increase the voltage by? Or would it remain the same?

Pictures from our lab: