THE STUDY OF VOLTAGE PRODUCED FROM CITRUS FRUITS
Keely Murphy
Cary Academy
ABSTRACT
The purpose of this study was to determine which type of citrus fruit produces the most voltage.
When copper and zinc are poked into the fruit, it becomes a wet cell and acts like a battery. A
copper wire and a zinc nail were both poked into four citrus fruits and each of the four fruits was
connected to a multimeter which measured the voltage. It was determined that the lemon and the
grapefruit produced the same amount of voltage and had the most voltage and the lime was
determined to have the lowest voltage. The fruit that were more acidic clearly produced more
voltage than the fruits that were less acidic.
INTRODUCTION
Voltage is a measurement of electrical pressure in a circuit. It measures the electric current that
travels from one end of a wire in a circuit to the other end. The current travels like that because
there is more potential energy on one end of the wire than the other. When power surges happen
the voltage increases in electricity lines. Power surges are caused by lightning strikes and the
electric pressure in the electrical lines is increased by millions of volts when a power surge
happens. If the increase of voltage in the electrical lines lasts for one or two nanoseconds it is
called a spike. If the increase in electricity lasts for three or more nanoseconds it is called surge.
The definition of voltage is literally an electromotive force or potential difference expressed in
volts. Voltage is also the potential energy that makes the electric current flow. It is the potential
difference between two points in an electrical field. Voltage pushes the electrons around as it
moves through a circuit. Voltage is basically the push in an electrical current. When there is
more current in the circuit, there is more voltage produced.
Fruit is made up of a mixture of chemicals that is called an electrolyte. An electrolyte allows
charges to flow. An electrode is the part of a cell through which charges enter or exit. Each cell
has a pair of electrodes from conducting materials. There are chemical changes between both the
electrodes and the electrolytes. These changes convert the chemical energy to electrical energy.
There are two kinds of cells in electricity. These two types of cells are wet cells and dry cells.
Wet cells are liquid cells like the cells in a car battery. A lemon also has wet cells which is a
reason why it acts like a battery and is able to produce voltage. Dry cells are paste like or solid
cells like the ones in a flashlight or a small radio. A lemon is able to convert to a wet cell when
copper and zinc are put in it. The lemon juice is the electrolyte and the zinc and copper are
electrodes. When both of them are put together, they create an electrical energy. The zinc and
copper are like the negative terminal in the battery and the lemon is the positive terminal. The
lemon has an acidic quality and that is another reason why the lemon acts like a battery. It is also
a reason why it can produce voltage. A lemon is a citrus fruit, which has citric acid, and a battery
also has acid. This is also true for other citrus fruits or fruits with a type of acid in them. Just one
lemon or one lime can’t light a light bulb because it doesn’t produce enough voltage to do that.
With four or five lemons or limes only a small LED bulb can be lit.
A multimeter is a digital meter that measures multiple things. It acts like a bunch of different
meters put together into one meter. A multimeter can be used for different purposes. It carries an
ammeter, a voltmeter and even a thermometer. An ammeter measures the amount of electrical
current that flows through a circuit. To measure current, an ammeter is connected in series in the
current. This is so that the ammeter can measure all of the current. The greater the current in the
circuit the higher the numbers are on the multimeter. The multimeter also carries a voltmeter. A
voltmeter is a meter that measures the amount of voltage in a circuit. To measure the amount of
voltage in a circuit, the voltmeter is connected parallel to the circuit. It is connected like this so
almost no current flows through it. The more volts that the circuit produces, the higher the
numbers are on the multimeter. The multimeter also carries a thermometer. A thermometer is a
meter which measures the temperature. It measures how hot or cold something is. A thermometer
measures the temperature of anything. The hotter the temperatures, the higher the numbers are
on the multimeter.
An experiment that has been done in the past is one that studied which citrus fruit produces the
most electricity. This experiment has been done by a prior 6th grade student named Kayla
Haeussler. Grapefruits, lemons, limes and oranges were tested. Each fruit was measured in
voltage. Different conductors were used and the results were that the lime produced the most
voltage. The lime had produced 0.996 V. The orange had the second highest with 0.961 V then
there was the grapefruit with 0.764 V. The fruit with the lowest voltage was the lemon with
0.720 V. The hypothesis was wrong. The hypothesis was that the lemon would produce the most
voltage because it is used most commonly as a fruit battery. The next experiment that was done
was testing each fruit with two screws and then two pennies. The lemon with the two screws had
the highest voltage with 0.994 V. The second highest voltage with the two screws was the orange
with 0.962 V and the next highest was the grapefruit with 0.846 V when it had the two screws.
The fruit with two screws that had the lowest voltage was the lime with a voltage of 0.789 V.
The orange had the highest voltage with the two pennies with a voltage of 0.949 V. The second
highest voltage with two pennies was the grapefruit with 0.932 V and the next highest was the
lime with 0.897 V. The lowest voltage with the two pennies was the lemon with a voltage of
0.332 V.
MATERIALS AND METHODS
In these experiments, lemons, limes, oranges, grapefruits, a multimeter, beakers, water, a zinc
nail, a copper wire, and pH strips were used.
The zinc nail and copper wire were poked into the grapefruit and then connected to the
multimeter. The multimeter measured the voltage of the lemon. This method was continued with
the orange, lemon and lime.
The lime juice was squeezed into a beaker as the zinc nail and copper wire were put into the
juice. The zinc nail and copper wire were connected to the multimeter which then measured the
voltage. This method was continued with the lemon, orange and the grapefruit.
A zinc nail and a copper wire were poked into an orange and were connected to a multimeter
which then measured the voltage. The copper wire was then poked into another orange where the
zinc nail stayed in the one orange. Both the zinc nail and copper wire were connected to the
multimeter which measured the voltage. This method was continued with the lemon and the
lime.
The lime juice was squeezed into the beaker as a pH strip was stuck into it. The pH strip then
measured the acidity of the juice. Then the copper wire and the zinc nail were stuck into the juice
and the pH was measured again. This method was continued with the lemon and the orange.
Water was poured into a beaker as a pH strip was stuck into it. The pH strip measured the
amount of acidity into the water. Ten drops of lemon juice were then added and the pH was
measured again. This method was continued as twenty drops and then fifty drops of lemon juice
were added to the water.
RESULTS AND DISCUSSION
Voltage Produced (V)
1
0.8
0.6
0.4
0.2
0
Lemon
Lime
Orange
Grapefruit
Type of fruit
Figure 1: Most voltage produced from citrus fruits
The lemon and the grapefruit were found to produce the most voltage (both producing 0.76 V)
out of the four citrus fruits that were tested. The lime was found to be the one with the least
amount of voltage (producing 0.61 V). Overall, the lemon and the grapefruit probably produced
the most voltage because it has a higher acidity than a lime or an orange. The more the acid in a
fruit, the more voltage it produces. This is because the citric acid in a fruit is acts like the acid in
a battery so the fruit can produce voltage.
0.74
Voltage produced (V)
0.72
0.7
0.68
0.66
0.64
0.62
0.6
Lemon
Lime
Orange
Grapefruit
Type of juice
Figure 2: Most voltage produced from fruit juice.
The grapefruit juice was found to produce the most voltage (producing 0.72 V) out of the four
types of fruit juices. The fruit juice with the least amount of voltage was the lemon (producing
0.64 V). This happened because the grapefruit juice didn’t have a voltage that was that different
from the grapefruit so the grapefruit’s voltage was not affected when it was pure juice. The
lemon juice on the other hand had a very different voltage than just the fruit. There were
probably some more qualities that give the whole lemon more voltage than the voltage of the
lemon juice.
0.8
Voltage produced (V)
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Two in one One in two Two in one One in two Two in one One in two
Lemon
Lemons
Orange
Oranges
Lime
Limes
Fruit with two or one probe
Figure 3: Voltage produced from citrus fruit with two probes in one or one probe in two
fruits
The two probes in one orange seemed to produce the most voltage (producing 0.67 V) and the
lime with one probe in each of two fruits produced the least amount of voltage (producing 0.003
V). Overall, having one probe in each of two of the same fruits did not produce a lot of voltage.
This happened because there was not much of an electrical connection between the two fruits
and two probes. The two probes in one fruit were what were normally done when the voltage
was tested from a fruit. If the voltage had to be tested of two fruits, there would have to be two
probes in each of the two fruits. There is a very clear result that putting the one probe into each
of two fruits did not produce a lot of voltage because there was not a lot of electrical connection
between the probes and the fruit.
6
acidty (pH)
5
4
3
2
1
0
lemon juice lemon juice lime juice lime juice orange juice orange juice
with copper
with copper
with copper
& zinc
&zinc
&zinc
liquid
Figure 4: Most acidity in fruit juice and fruit juice with copper and zinc
It was found that the lemon is the most acidic of the three fruits (having a pH of 2). The orange is
the least acidic (having a pH of 5). Putting the copper and zinc in did not change the acidity at
all. Overall, the lemon was the most acidic because it is one of the more sour fruits. The lemon
also has more citric acid than the lime or the orange. A fruit like the lemon has a lot of citric acid
so its pH was lower. The lower the amount of acid the higher the pH is. A lime also has a lot of
citric acid, but not as much citric acid as the lemon had.
7
6
acidity (pH)
5
4
3
2
1
0
water
ten drops of
lemon juice
twenty drops of
lemon juice
fifty drops of
lemon juice
liquid
Figure 5: Highest acidity when lemon juice is added to water
It was found that fifty drops of lemon juice in water had the most acidity (with a pH of 4) and
water alone had the least amount of acidity (with a pH of 6). This happened because the lemon
juice had the most citric acid. Putting lemon juice into water would make the water more acidic
and make the pH level lower. The more lemon juice put into the water the more acidic the water
became. The pH level got lower as more lemon juice was put into the water. When something is
more acidic, the pH level gets lower. That was what was happening as the amount of lemon juice
was increasing in the water.
CONCLUSION
The citrus fruits were tested to see how much voltage was produced. My hypothesis was correct
because my hypothesis was that the lemon would produce the most voltage because it is most
commonly used as a fruit battery. These results will be important to people when their power
goes out and they can used some lemons to power a light bulb for light. A future experiment that
could be done is testing other fruits that are not citrus fruits.
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