Introduction: (Initial Observation)
Before invention of electric generators, battery was invented. Battery is a device that converts chemical energy to electrical energy (Electricity).
For many years scientists used electricity from batteries and made electromagnet and devices that are based on electromagnet such as telegraph, microphone, speaker, buzzer, telephone and electromotor.
Batteries use the reaction between three or more substance to create a flow of electrons. In this project you will study different chemicals that can be used to make a battery and specially focus on fruits and fruit juice as chemicals in your experiments.
Information Gathering:
What is electricity and how is it made?
Electricity is moving electrons in a conductor such as a copper wire. But what can force these electrons to move? There are two different ways that electricity can be made.
First method is using a chemical reaction. For example batteries make electricity by a chemical reaction.
Second method is by using magnet. Moving magnets next to a wire, can force electrons move inside the wire.
For making electricity using magnet, check the following links for information:
Making electricity using magnet is not a simple experiment, specially if you want to produce enough electricity to light up a bulb. So most likely you are nor going to make an electric generator for your project; but drawings in the above sites may be reproduced in a larger size and be used in your display.
For making electricity using a chemical reaction, visit this link:
Question/ Purpose:
What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.
The purpose of this project is to see how much electricity we can make using two different metals and an electrolyte such as lemon or other fruits.
Identify Variables:
When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.
Independent variable (also known as manipulated variable) is the type of electrolyte or fruit that we test (Lemon, potato,…).
Dependent variable (also known as responding variable) is the amount of electricity that we produce.
Controlled variable is the temperature. (Controlled variables are all other variables that may affect the amount of electricity. Temperature may accelerate chemical reactions)
Constants are:
- Type and size of electrodes (We use copper and zinc for all experiments)
- Contact area of electrodes with electrolyte
Hypothesis:
My hypothesis is that the amount of electricity made from lemon is more than the amount of electricity made from potato.
Note: You can come up with your own hypothesis.
Experiment Design:
Read the following instructions and experiment making electricity using different fruits or fruit juices.
Make electricity from a lemon (or potato)
Electricity can be made by some chemical reactions. This method is used in batteries and creates direct current (DC). Here is a sample recipe of making electricity in chemical way. Material that you need for this experiment are:
- citrus fruit (lemons or limes work best)
- Copper electrode about 12 cm long, 4 cm wide (5 x 1.5 inches)
- Zinc electrode about 12 cm long, 4 cm wide (5 x 1.5 inches)
- One small light bulb (1.3 volts)
- Socket for light bulb
- Wire gauge 24 or similar
- Alligator clips
Step by step instructions:
1. Roll the fruit under the palm of your hand to soften but be careful you don’t break the skin. Work it gently on a piece of scrap paper or a paper towel. (If you are using potato, skip this step)
2. Mount your bulb socket (base) on the board, cut about 1.5 feet wire and carefully remove the insulation of about 1″ on each end of your wires.
3. Connect one end of each wire to an alligator clip and the other end to the bulb socket.
4. screw the bulb and use a small AA size battery to test your bulb. (To do this connect alligator clips to the poles of your battery, light bulb should lit.)
5.Insert the electrodes into the fruit about 5 cm apart. Don’t allow the electrodes to go through the bottom skin of the fruit. If your electrodes are large sheets, cut as much as you need.
6. Connect alligator clips to the electrodes. You have light!
Important notes:
- If you just use a Voltmeter to show the electricity, you get a better result because small amount of electricity can simply move the needle of a volt-meter, but can not turn on a light bulb.
- More metal surface in contact with fruit results more electricity. Since the produced electricity is so little, you have little chance on turning on a light, but you can definitely show the produced voltage using a multi-meter and you can use that electricity to turn on a digital clock or small digital calculator, because these two need much less electricity than a bulb.
- Investigate the probability of using other fruits and vegetables to make electricity. Measure the pH of each “battery” and see if there is a relationship between the pH of the juice and the amount of light that is produced. If you have a multi meter, you can measure the voltage and current produced. You can measure pH using a pH paper.
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| In this sample we are using a copper sulfate solution as an electrolyte (plus a few drops of sulfuric acid). One electrode is copper and the other is zinc. It created 0.9 volts electricity that was able to turn on a 1.2 volts light bulb for about 1 minute. |
Light up an LED
L.E.D. or Light Emitting Diode is an electronic light source that needs less electrical current to light up. Use of LEDs instead of miniature light bulbs is recommended by ScienceProject.com because with LEDs, students will have a better chance to get a visible light in their experiments.
2-volt LEDs are available at MiniScience.com
Although LEDs do not require much current, they need a minimum voltage of about 2.2 volts.
Each fruit battery usually creates about one volt. To get a higher voltage you will have to connect 2 or more fruit batteries in series. To do that, you use alligator clip wire leads to connect the copper (+) electrode of one battery to the Zinc (-) electrode of the next battery. At the end, you will connect the LED to the Zinc electrode of the first battery and copper electrode of the last battery.
We used (+) and (-) above just to remind you that copper is always the positive electrode and zinc is the negative electrode.
Identifying the polarity or direction of electricity is especially important when you are trying to light up an LED.
Each LED has 2 legs. One is longer than the other. The longer leg must be connected to the positive pole of the battery or copper. The shorter leg must be connected to the negative electrode or Zinc.
If you don’t have enough copper and zinc electrodes, you may cut your existing electrodes in half and make 2 electrodes form one; however, remember that electrodes cannot be very small. The surface contact of the electrodes with the fruit must be as much as possible in order to get the most electric current.
Question: I used 3 apples to light up the L.E.D. and I was successful but when
I used 3 apples to light up the 1.2 volts light bulb, I wasn’t
successful? How come?
Answer: 3 apples produce about 3 volts (1 volt per apple) and that is enough for either LED lamp or Incandescent lamp; however, the incandescent lamp needs more current than the LED lamp. The amount of current depends on the size of electrode and the surface of electrode in contact with fruit. You must use larger electrodes to produce higher current.
The other solution is to connect 3 apples in parallel. This may work if enough current is produced. In a parallel connection you will connect all copper electrodes to each other and all zinc electrodes to each other. Doing this is almost like having a larger electrode.
Make Electricity from Copper Sulfate Electrolyte
For this experiment we decided to use copper sulfate as electrolyte because copper sulfate is widely available at hardware stores and pull suppliers. You can also get small sheets of copper and zinc from hardware stores. If you could not find zinc, just get a galvanized iron. It does the same thing in a few seconds until the layer of zinc is destroyed. You will need to add a few drops of sulfuric acid for the process to speed up and turn on the light. Sulfuric acid also is known as battery acid and can be purchased from auto parts store. You need diluted sulfuric acid (about 5 to 10%). Acid sulfuric is very corrosive and you must have gloves, goggles and protecting clothing while handling it.
Material needed are:
- 2 plastic or ceramic cup
- 2 sheets of copper (2″ x 4″)
- 2 sheets of zinc (2″ x 4″)
- 50 grams copper sulfate
- 10 cc Sulfuric Acid 10%
- One 1.2 Volts bulb with socket
- Three wires (with alligator clips if possible)
- One Multi-meter (Set to Voltage)
In the first experiment, secure a copper plate and a zinc plate on the sides of the cup as your electrodes. As the picture shows you can bend the sheet toward outside. Use two wires to connect the electrodes to the light bulb holder and screw the bulb. Temporarily remove the zinc plate and then fill up the cup with copper sulfate solution. Now insert the zinc electrode.
Although the process starts and electricity is being produced, the light bulb may still be off. Add a few drops of sulfuric acid to expedite the process and get some light. To stop the process remove the zinc plate. If you want to test the voltage, make sure you unscrew the bulb first.
This process will release hydrogen that is hazardous and breathing that will cause choking. So do the experiment in a well ventilated place and avoid keeping your head right above the cup.
This chemical reaction creates about 0.7 volts that is barely light up a 1.2 Volts bulb. But is not able to light up a 2.5 volts bulb that is shown in this picture.
In the next experiment we connected two cups together as shown in the picture. That created about 1.2 volts and produced a small light on our 2.5 volts bulb.
Now you know why I insist on low voltage bulb for this test.
This picture shows the bulb in the last experiment.
Testing other electrolytes such as salt water and lemon juice produced much less electricity and no lights at all.
Multi-meter showed that each cup is producing 0.7 volts and 5 cups together produced 2.3 volts.
Even though we had 2.3 volts of electricity, it could not turn on the light. The reason is that small electrodes can not create enough electric current.
Latest Update: (Make a Sandwich)
This new experiment using copper sulfate produced a long lasting bright light.
Procedure:
Make about 30 mL saturated solution of Copper Sulfate.
Cut 2 pieces of felt about 1/2″ smaller than your copper and zinc plates both in length and width.
Place one copper electrode on the table and connect it to one side of the light bulb.
Insert one piece of felt in saturated copper sulfate and place it on the center of the copper plate.
Place a zinc plate over the felt.
Place another copper plate over the zinc plate.
Insert another felt in copper sulfate and then place it on the center of the top copper plate.
Finally place another zinc on the top and connect that to the other side of the light bulb. You should get the light.
* Notes:
- Felt should get wet, but it should not have any excess liquid running off the felt.
- You may substitute the felt with any thick, absorbent cotton fabric.
Experiment 1: Compare different fruits for their ability to produce electricity.
Introduction: Fruits and fruit juices can be used as electrolyte in a fruit battery with copper and zinc electrodes. The amount of produced electricity depends on the soluble acids and minerals in each fruit. In this experiment you will compare different fruits and vegetables for the amount of electricity they produce. You will then use your results table to draw a bar graph:
Procedure:
- Insert one copper electrode and one zinc electrode in each of the fruits or fruit juices you want to test.
- Set your multi-meter or voltmeter to 2.5 Volts DC or closest available range to 2.5 volt. (DC stands for Direct Current)
- Connect the probes of the voltmeter to the copper and zinc electrodes. The red wire (+) must go to copper and the black (-) must go to Zinc.
- Read and record the voltage when the needle stops moving.
- Repeat this three times with each fruit and then calculate the average of voltages you got in your three trials. Record the average as the final voltage of that fruit in your results table.
Your results table may look like this:
| Fruit or vegetable | Voltage |
| Orange | |
| Potato | |
| Apple |
Make a graph:
Use your results table to make a bar graph. Make one vertical bar for each of the fruits you have tested. The height of that bar will represent the voltage you got from the fruit it represents. Write the name of fruits under the bars.
What is the control in this experiment?
You can have another pair of electrodes inserted in an empty cup as a control. In this way you will show that electrodes do not make any electricity by themselves if they are not inserted in an electrolyte such as fruit or fruit juice.
Materials and Equipment:
List of materials:
- Galvanometer or voltmeter capable of showing millivolts. (Can be purchased from electronic stores or online from MiniScience.com)
- A small Light bulb with base. (1.2 Volts bulb is the best and you will have more chance to see some light)
- A piece of Zinc metal to be used as Zinc Electrode. (Hardware stores sell zinc screws. Those are steel screws coated by zinc. They can be used for quick experiments, however they will not work as soon as the zinc layer is dissolved in the electrolyte. For best results you can buy Zinc online)
- A piece of copper metal (can be purchased from hardware stores. I have used copper pipe and it worked well.)
| Multimeters used as Galvanometer or Voltmeter:Any multimeter that can measure low range DC voltage may be used to measure the output voltage of your Air/Saltwater battery. Two common models are AMM360 and YG188. | |
Multimeter model YG188:YG188 is an analog multimeter for general electrical use.
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| Multimeter model AMM360:
AMM360 is a desktop analog multitester for measuring DC Volt, AC Volt, DC Current and Resistance. AMM360 can be used as a very sensitive galvanometer and can show as low as 0.01 DC voltage. AMM360 can also be used to test transistors and diodes. |
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Where to buy?
Following online stores are affiliated or approved by ScienceProject.com for all materials you may need for this project.
Results of Experiment (Observation):
Write the results of your experiments in a table like this.
| Electrolyte (Fruit name) | Maximum voltage | Light condition |
| Lemon | ||
| Apple | ||
| Potato | ||
| … |
In the first column write the name of fruit or electrolyte solution that you may test. In the second column write the voltage in volts or millivolts. In the last column write if the light came on or not.
Calculations:
No calculations is required for this experiment.
Summary of Results:
Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.
It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.
Conclusion:
Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.
Related Questions & Answers:
What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.
Possible Errors:
If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.
If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.
Does degreasing and cleaning electrodes from oil and grease affect the amount of voltage?
References:
List of References
http://chemlearn.chem.indiana.edu/demos/Zinc.htm
http://quiz2.chem.arizona.edu/preproom/Demo%20Files/cu-zn_battery.htm
To find more references, search the Internet for Voltaic Cell or Galvanic Cell. What you are making in this project is really a voltaic cell; however, you are using fruit juice instead of chemicals as Electrolyte.
Why do we need a control?
When you finish your experiments and report your results, someone may question the reliability of the results and suggest that possibly some unknown conditions may have affected the results. That is why you also do another experiment known as control experiment in which you eliminate your manipulated variable. This is a possible scenario with this project:
You may report or say: Lemon made the most voltage!
I say: How do you know?
You say: I experimented and measured the voltage made by lemon.
I ask: At what time?
You may look at your notes and answer: At 9:25 a.m.
I ask: How can you be sure that at 9:25 a.m. another unknown factor such as solar activities or changes in room temperature or … was not the cause of high voltage?
Now is the time that you must show a control. If you have a control
You may say: I had a control using an identical voltmeter and an identical set of electrodes in an empty plastic cup (or a cup of water) and they did not show any voltage increase. If solar activities or other factors (other than lemon) wanted to increase the voltage at the time of my Lemon experiment, they would also cause a voltage increase in my control experiment.
