Testing the Voltage of different Fruit Combinations when used as Electrochemical Cells
In science we had to design an experiment that involved electric circuits using fruits as electrochemical cells. My group’s question was “What will happen to the voltage [of the circuit] when we change the combination of fruits?”.
You can read further on what this actually means in the lab report, but essentially, we tested the amount of voltage we could produce with two fruits by testing out different fruit combinations.
Lab report:
Measuring the Electrical Properties of Pairs of Fruit
Question:
What will happen to the voltage when we change the combination of fruits?
Claim:
The pair of fruit with the most volume will produce a greater voltage than any other combination from the fruit provided (2 oranges, 2 lemons, and 2 grapefruits)
Hypothesis:
If the fruit combination changes, then the Voltage will change
Controlled Variables:
- Slits are made 2cm apart
- Slits are 3cm long each
- All pairs of fruit are the same brand
- Same copper strips
- Same zinc trips
- Fruits are all at room temperature
**The same materials are consistently used for each individual fruit trial**
Materials:
- Two copper strips (13 cm by 2 cm by 1mm)
- Two zinc strips (13 cm by 2cm by 1mm)
- Three pairs of Crocodile clips
- Two Lemons
- Two Grapefruits
- Two Oranges
- One Voltmeter
- One Ruler
- Paper Towels
- Steel Wool Pad
- Knife
- Safety Goggles
- One sharpie
Observations
- The voltage went down the longer the fruit was plugged in for. This could be due to several factors.
Procedure:
- Put on Eye Protection
- Lay down Paper Towels on clear table
- Scrape metal strips with steel wool (both copper and zinc) to clear them of oxidization
- Label each fruit with an A or B (this will determine whether they will be used in trial 1 or trial 2)
- Cut 3 cm slits into the two pieces of fruit, spaced 2 cm apart
- Insert the metal strips into the fruit, putting a pair of one copper and one zinc into each one
- Hook up voltmeter with crocodile clips
- Attach crocodile clips onto the Voltmeter, using the negative and 3V ports
- Attach crocodile clips to inserted metal strips, making sure to have copper connected to zinc to form a circuit (Voltmeter connected to copper, zinc connected to copper, zinc connected to voltmeter)
- Read voltmeter and record results within the first 10 seconds as for some unknown reason the voltage drops rapidly
- Repeat steps 4-8 with the other fruit combinations as many times as required, each time cutting new slits into the fruit that you’re using.
Results:
Table 1: Control Groups
| Fruits | Lemon A (original set of slits) + Lemon B (original set of slits) | Orange (third set of slits) + Orange B (original set of slits) | Grapefruit A (third set of slits) + Grapefruit B (original set of slits) |
| Voltage after 10 sec | 0.95 | 0.25 | 0.65 |
Table 2: Trial One (fruit As)
| Fruits | Lemon A (second set of slits) + Orange A (original slits) | Lemon A (third set of slits) + Grapefruit A (original slits) | Grapefruit A (second set of slits) + Orange (second set of slits) |
| Voltage after 10 sec | 0.35 | 0.6 | 0.55 |
Table 3: Trial Two (fruit Bs)
| Fruits | Lemon B (second set of slits) + orange (second set of slips) |
| Voltage after 10 sec | 0.3 |
Justification:
We think that the lemons produced the largest amount of voltage because they have the greatest number of electrolytes. Our hypothesis was that the grapefruit would produce the most voltage because it was the largest, but the pair of two lemons ended up producing the most voltage. This may be due to the higher concentration of citric acid in the lemons, even though the grapefruit is physically larger. As expected, the orange produced the least amount of voltage due to its low concentration of citric acid and thus a sweeter taste. We think that the lemon and the grapefruit probably had a similar number of electrolytes in total, but the it was more concentrated in the lemon, therefore providing less options for the free electrons and forcing them to go to the voltmeter.
Three Digital Criteria I used:
- “I constructively buil[t] upon or synthesiz[ed] the ideas of my peers.” (no. 4)
Because this was a group project, a major aspect of it was collaboration. When one group member had an idea, it was important to approach it with both critical and creative thinking. In the early stages of the project, when we were designing the experiment, we started with the idea of doing a lab with the same properties as the our final design, but with one parallel circuit and one series. We then realized that in our situation, a parallel circuit wasn’t a good choice. So, while we originally had one idea, by running it through all four of our heads, we made an educational decision to change the overall design.
- “I us[ed] digital spaces to plan and execute collaborative projects with my peers.” (no. 1)
We used office 365 as a digital platform for sharing our ideas and of course writing our lab report effectively in a collaborative manner.
- “I tailor[ed] my work to appeal to my intended audience, and us[ed] language and visual elements appropriate for them.” (no. 2)
Because our only audience was our teacher, we didn’t have to worry about making things too complicated as we knew our teacher would understand and, in the end, it would most likely seem trivial compared to what they know.