The Effect of Using Various Fruits and Vegetables On

The Effect of Using Various Fruits and Vegetables on

the Ability to Power Small Light Bulbs

Jesse Matthews

Takoma Park Middle School 2011 – 12

Abstract

The question of this experiment was how many halves of common types of fruits and vegetables are needed to light a light bulb, with the potential application of produce serving as an alternative, more environmentally friendly, energy source. The produce types tested included apple, banana, celery, kiwi, lemon, lime, onion, orange, potato, sweet potato, tomato, and yellow squash. The hypothesis was that the more acidic produce types would require fewer pieces of produce than the more chemically neutral ones to light a 1.7 volt LED light bulb. The setup included a half piece of produce with a zinc screw and non-insulated copper wire punctured into it in two places. The two prongs emerging from the bulb were then connected, one to the wire and one to the screw. If the bulb did not light, another piece of produce was added to the setup in series until the bulb lit. Each produce type was tested five times. Acidic produce types were found to require up to two pieces fewer to light the bulb than more chemically neutral ones, supporting the hypothesis. Kiwi, lemon, lime, orange, and tomato required only three pieces on most trials to light the bulb, while celery, onion, potato, and, surprisingly, apple needed four. Such large amounts of produce to generate about a volt for each half does not make produce a practical energy source. Perhaps in the future, produce scraps could be tested for their ability to provide energy to help power equipment at produce packing plants.

Key Terms: Electrical Output, Battery, Produce, Anode, Cathode, Electrolyte

TPMS Journal of Science Page 1 of 7 The Effect of Using Various Fruits and Vegetables on the Ability to Light Up Small Light bulbs

Introduction and Review of Literature The question studied in this experiment was “How many halves of common types of fruits and vegetables are needed to light up a 1.7 volt LED light bulb?” The findings would hopefully help answer the question of whether fruits and vegetables could be used as a source of energy. If any of the studied produce seemed to provide adequate energy, it could potentially be an efficient alternative energy source that would involve little negative environmental effects, as the produce is all biodegradable and relatively abundant. If a viable energy source were found, this could have a positive environmental effect by helping to reduce human reliance on oil, natural gas, and electricity.

The hypothesis is that if the electrical output of apple, banana, celery, kiwi, lemon, lime, onion, orange, potato, sweet potato, tomato, and yellow squash are tested, then the produce containing the more acidic juices, such as kiwi, lemon, and lime, will need fewer pieces of produce in a circuit to light up a light bulb than the more pH-neutral types of produce, such as celery, onion, and potato, because the acid in the more acidic produce would react with the zinc to produce electricity. Also, these results are shown in the study “Lemon Cell” by Jerry Goodisman of the Department of Chemistry at Syracuse University in that the more acidic produce produced more electricity than the less acidic ones.

Every battery contains an anode, which is a negative electrode, a cathode, which is a positive electrode, and an electrolyte which pushes the electrons through the battery. The fruit’s juice acts as the electrolyte, and the anode and cathode are the copper wire and the galvanized iron nail, respectively, in this experiment. The result, electricity, is defined as a form of energy that is expressed in terms of the movement and interaction of electrons. It can be used as an energy source, as in this example, to light up light bulbs.

The dependent variable for this experiment is the number of produce halves need to light up the light bulb. The independent variable is the type of produce used, with levels being fruits and vegetables that are commonly found in grocery stores year round— apple, banana, celery, kiwi, lemon, lime, onion, orange, potato, sweet potato, tomato, and yellow squash. In order to ensure accurate results, other variables were controlled during this experiment. Controlled variables include the voltage needed to light up each bulb, the conductivity of each insulated copper wire piece, the tester, the room temperature and humidity, and the juiciness, ripeness, and size of each piece of produce. LED lights are used due to their low requirement of electrical input necessary to power them, and the produce were chosen because they are common types, including ones known to have high levels of acidity, which is shown to help produce more electricity.

A previous study, “Lemon Cells Revisited–the Lemon Powered Calculator,” by Daniel J. Swartling and Charlotte Morgan of the Department of Chemistry at Tennessee Technological University, shows that a single lemon can only produce about one volt of electricity. Thus, this means that one lemon cannot provide enough electricity to power one of the 1.7 volt light bulb used in the present experiment. However, Swartling and Morgan’s data also shows that whenever another lemon is added in a chain to their setup, the voltage output is increased by about 0.9 volt, the electrical output of one lemon. Accordingly, three lemons in a chain should be able to light up the 1.7 volt LED bulb. Finally, the article states that since magnesium is a more active element than zinc, in terms of movement of electrons, using magnesium will produce more electricity than using zinc; and, therefore, the same number of lemons should produce more volts of electricity to light the light bulb when using magnesium instead of zinc.

The previously mentioned study, “Lemon Cell” by Jerry Goodisman of the Department of Chemistry at Syracuse University, demonstrates that other types of produce or even water with an added acid, for example citric acid, can produce just as much energy as the lemon. Also, it shows that any acid can work well to produce energy in an aqueous solution. Furthermore, this study finds that many other metals besides zinc and copper perform well as the anode and the cathode. Finally, this experiment illustrates the potential of producing energy basically by dipping two metals into citric acid and observing how much energy is produced as a result of the electric flow between the two metals. Goodisman’s study is related to the present study because it implies that using one of the acidic fruits with a nail and wire should result in sufficient electric flow to light the LED bulb.

Materials and Methods

In this experiment, the amount of electricity that could be produced using various common fruits and vegetables was tested. The materials necessary to complete this testing were one 1.7 volt miniature LED light bulb with base wires attached, three feet of insulated copper wire, three each of twelve different fruits and vegetables to be tested (apple, banana, celery, kiwi, lemon, lime, onion, orange, potato, sweet potato, tomato, and yellow squash), a cup of distilled water for the control, a towel, a zinc coated nails, a wooden surface top, and a kitchen knife to cut the fruits and vegetables. The conducting wire was cut into six pieces of approximately equal length to be used to connect the produce pieces to each other and to the light bulb to complete the circuit.

For the first produce type to be tested, a lemon, the kitchen knife was used to cut the fruit in half. One half was used for the first trial, and the other half was saved for later in the first trial, if it was needed. Additional lemons were also cut in the case that three or more of the produce halves were needed. All work was done on a wooden surface, which did not conduct electricity well and did not interfere with testing the ability of the various produce types to produce electricity. The zinc nail was inserted into one end of the lemon piece and one of the six wire segments into the other end. The free end of the wire segment was attached to one of the base wires of a light bulb. The other base wire of the light bulb was attached to the zinc nail, which formed an electrical circuit, and it was noticed whether the light bulb was at least partially lit. If it was, one was recorded for the lemon in a lab book, and the first trial was complete. If the bulb did not at least partially light up, then another lemon half was added with a zinc screw and a piece of copper wire punctured into it again. The zinc screw from one half of the fruit was attached to the copper of another, and the remaining copper wire and zinc screw were attached to the light. It was observed whether the light bulb was at least partially lit. If so, two was recorded for lemon in the data book, and the first trial was complete. If the bulb was not lit, another produce half was attached in a similar manner to how the second produce half was attached to the first produce half. After completing the electrical circuit, it was noticed whether the light bulb was at least partially lit. If so, three was recorded in the data book and the first trial was complete. If all three produce halves were unable to lighten the light bulb, then a fourth half was added. In this manner, this procedure was repeated for up to five light pieces, and it was determined whether one, two, three, four, or five fruit halves were needed to at least partially light the light bulb. The setup for three lemon halves is illustrated in Figure 1. Using the same produce halves but in different spots in the produce, this procedure was repeated four more times to yield five trials for the lemon. These five trials also allowed for a mean number of fruit halves needed for the lemon to be calculated. Next, five trials were completed for the lime, and then five for each of the orange, apple, potato, tomato, banana, kiwi, yellow squash, celery, sweet potato, and onion.

To serve as a control, approximately a tablespoon of distilled water was poured onto the wooden surface, and one end of a wire segment was placed in one end of the water puddle and the zinc nail in the other end of the puddle. In this manner, the puddle of water could substitute for a piece of produce to see whether zero, one, two, three, four, or five puddles of water were needed to at least partially light up the bulb. Water was chosen because each of the produce types is moist, yet water is not acidic. The puddles used were dried using the towel, new puddles were made, and results were obtained for the remaining of the five trials using water. This control result provided baseline information on the ability to light up any bulbs using the proposed setup without an acidic type of produce.

Although testing conditions were controlled as much as possible, various uncontrollable factors could have interfered with obtaining reliable results. These factors included differences in conductivity in various parts of the insulated copper wire, human error in making electrical connections or reading results by the tester, and differences in size and chemical properties of fruits or vegetables of the same type.

Results

The number of produce of a certain type required to light up a single bulb varied only slightly among the twelve types of produce tested. Half of the produce types tested—banana, lemon, lime, sweet potato, tomato, and yellow squash—required three produce on each of the five trials to light the bulb, as can be seen in Table 1 under the columns corresponding to these six types of produce, as well as in the colored bars corresponding to each of these produce types in Figure 2. Two others—kiwi and orange—required three produce on at least two of the five trials, producing a mean over all trials that is close to three—2.4 and 3.6, respectively, as reported under the columns for kiwi and orange in Table 1 and the kiwi and orange sets of colored bars in Figure 2. The remaining four produce types tested—apple, celery, onion, and potato—needed four pieces of produce to light the bulb on each of the five trials. This result is also seen in Table 1 under the columns for apple, celery, onion, and potato and the colored bars for each of these types of produce in Figure 2. In addition, even five puddles of distilled water failed to light the LED bulb, strengthening the argument that the acid in the produce juice resulted in more electricity produced. Since there was no number of puddles that resulted in the bulb being lit, water was omitted from Table 1 and Figure 2.

Furthermore, the number of pieces of produce of a certain type needed to light up a single bulb remained most often constant, and if not, varied only slightly among the five trials for a single produce type. Of the twelve produce types considered, only two—kiwi and orange—showed any variability among trials. Kiwi readings varied from two to three pieces of produce, and orange readings varied from three to four pieces of produce, as shown in the kiwi and orange columns in Table 1 and the kiwi and orange bars of various heights in Figure 2. For all other types of produce, readings for each type of produce remained the same over the trials, as shown in Table 1 and in the equal height of the colored bars corresponding to each produce type in Figure 2.

In conclusion, the number of pieces of produce required in series to light up the LED bulb varied only from two to four pieces of produce and remained constant throughout the five trials for each produce type in all but two cases. This resulted in banana, lemon, lime, sweet potato, tomato, and yellow squash requiring three pieces over all five trials, and apple, celery, onion, and potato requiring four pieces over all five trials. Kiwi needed two pieces on three trials and three pieces on two trials, and orange needed three pieces on two trials and four pieces on three trials to produce averages over the trials of 2.4 and 3.6 pieces of produce, respectively.