Introduction: (Initial Observation)
Making electricity from chemicals is based on the same scientific principles on which all modern batteries work. You insert copper and zinc electrodes in a chemical solution (electrolyte) and produce some electricity from the chemical reaction between your electrodes and electrolyte.
In a potato battery, the electrolyte will be a potato, not a synthetically made chemical. Potatoes are safe to handle so all students can try this project safely.
Potatoes contain a number of important vitamins and minerals. A medium potato (150g/5.3 oz) with the skin provides 27 mg vitamin C, 620 mg of potassium, 0.2 mg vitamin B6 and trace amounts of thiamin, riboflavin, folate, niacin, magnesium, phosphorus, iron, and zinc. Almost all of these minerals participate in or contribute to the chemical reaction with the electrodes resulting an electric flow.
Potato More about potato battery science project:
Potato battery science project is one of the most famous electricity/ Chemistry projects that can be performed successfully by most students in the age range of 10 to 16. It helps students to learn about producing electrical energy using chemical energy. Since the same method is used to get energy from many fruits and chemicals, this project can have many other names as well.
Key to success:
The electrical voltage and current produced by potatoes are at a very specific range. Considering the fact that each electrical device such as a light bulb or electric motor also have certain requirements to operate, potato battery project is a very educational and challenging project. When you purchase the materials of this project as a kit, you are sure that all the components have been tested and have been qualified for your experiments. Pre-qualified materials will greatly increase your chance to successfully complete your project. It is also important to perform the experiments exactly as suggested in this project guide. Deviation from these instructions are not recommended for students who are trying this project for the first time.
Find out about batteries and how they work. Read books, magazines or ask professionals who might know in order to learn about different schemes you may connect multiple batteries in order to increase the voltage or to increase the current. Keep track of where you got your information from.
What you need to know before trying the “Potato Battery” Experiments
Potato battery experiments are for students in grades 5th and up. Students need to have a good understanding of how electricity works before trying to produce it. Students must also have the basic skills and abilities of a normal person with no major disability. They must be able to use tools such as knives, scissors, and screw drivers. This project is not recommended for people with physical or mental disabilities. If you have the necessary skills, but lack the basic knowledge of electricity and conductivity, please read this page and try the suggested experiments. These are pre-requisite for the Potato Battery project.
Light up a light bulb
You must be able to light up a small light bulb (included in your kit) with a regular 1.5-volt battery (Any size battery will work fine. The most common sizes are AA, C or D size).
- Screw the light bulb into the base.
- Connect a red wire to one of the screws on the base.*
- Connect a black wire to the other screw on the base.
- Connect the red wire to the + pole on the top of a battery.
- Connect the black wire to the – pole at the bottom of the battery.
- The light bulb must light up. If it does not, check the connections and check the wires. Replace wires if needed.
*How can I do that?
If you are using connection wires with alligator clips on both ends, you can simply push the head of the alligator to open the jaws and hold the contact screw of the light bulb between the jaws. Alligator clips provides a relatively secure and fast temporary connection for your experiments. If you are using regular insulated wire, you must first remove some insulation from the ends of the wire for your contacts. Then loosen the screws on the base and place the bare end of the wire under the screw and tighten the screw.
Connections to the battery are simple touch. More secure connections with battery require a battery holder.
After you successfully light up a light bulb using a battery, then you can proceed to the next step and test your battery using a voltmeter.
- Set your multimeter to DC Volts 2.5. At this setting your meter can measure the voltage of any Direct Current electricity up to 2.5 volts.
- Connect the red probe of the meter to the positive (+ ) pole of the battery.
- Connect the black probe of the meter to the negative (-) pole of the battery.
- Read the voltage on the meter at the row numbered from 0 to 250; however, remember that your actual reading is 1% of the apparent reading. In other words if you read 70 in 0-250 scale, it really means 0.7 in 0-2.5 scale.
If you can successfully read the voltage of a battery, then you can go to the next step and make your first potato-battery. The most important step after making a potato battery is measuring the voltage.
Do I need to understand Voltage and Current before trying the Make Electricity project?
If you want to be able to light up a light bulb, you must understand the voltage and current. Otherwise you can only show the production of electricity using a Voltmeter.
In your kit you will have two different types of light. One is an incandescent light bulb with a screw base. This type of light require high current. The other is an LED (Light Emitting Diode) that requires high voltage.
If you don’t know about current and voltage, read this:
Voltage and Current
Part of the reason why electricity seems so mystifying is because you can’t see it. But such things as voltage, current, etc can be explained by imagining electricity in cables as if it was water flowing in a pipe. VOLTAGE is the “pressure of electricity”, and CURRENT is the flow-rate.
CURRENT is measured in AMPS. If electrons are the atoms of electricity, you’d see six million million million of them flow per second for each amp of current there is. (electrons are very small – many household appliances have several amps as a working current).
Changing Voltage and Current
If you are using batteries as the source of electricity, then you must know that usually larger cells provide higher current. For example alkaline batteries in sizes AA, C and D have the same voltage, but C cells can provide higher current than AA cells. D cells can provide higher current than C cells.
To increase the voltage you may connect 2 or more cells in series. Connection in series means that you connect the positive pole of one cell to the negative pole of the other.
To increase the current, you may connect 2 or more cells in parallel. Parallel connection means that you connect the positive poles together and the negative poles together.
Some Potato Types/ species
Red Bliss Potato
While buying potato, pay attention to the label so you know what type of potato you are buying.
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 make a potato battery. In the first step you will use a voltmeter to show that the potato can produce electricity. You will then try to use the electricity from potato to light up a light bulb.
Higher grade students will also compare different potatoes to find out:
Which potato creates the most amount of electricity? (This will be an experimental project that you complete using scientific method. Experiment 4 is for this question.)
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.
This is a sample of how you may define variables: (See Experiment 4)
- Independent variable is the type of potato. (Possible values are Russet also known as Idaho Potato, Red Bliss Potato, Desiree, Makoikoi, Urenika, …)
- Dependent variable is the electrical power. (Measured as voltage, in a closed circuit, while you have a low current lamp in the circuit.)
- Constants are the size of electrodes and the area in contact with potato (or potato juice).
- Control variable is the temperature (Air temperature as well as the potato temperature).
Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.
This is a sample hypothesis: (Tested in Experiment 4)
I hypothesize that different potatoes will produce different amounts of electricity. My hypothesis is based on my gathered information about different species of potato and different chemical composition of each one. I also think that the amount of minerals in a potato depend on the type of soil and mineral content of the soil. In other words it is possible to find different potatoes of the same species that produce different amounts of electricity.
Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”
Experiment 1: Producing electricity from a Potato
In this experiment you will show that potato or potato juice can make electricity. You will also have a chance to practice with your voltmeter and set it up correctly.
To make potato juice you may use an electric juicer or a grinder.
- Get a copper electrode and a zinc electrode. Wash them with liquid detergent and warm water to make sure they are free from oil and rust.
- Insert the copper and zinc electrodes in a large potato so that they are not touching each other. Part of the electrode must remain out of the potato or potato juice as a contact point for your potato battery.
- Set your multimeter to read 2.5 Volt Direct Current by turning the large knob. This may be marked as DCV or Volt DC (depending on your multimeter).
- Use the red alligator clip connection wire to connect the red probe of the multimeter to the copper electrode. Copper will be the positive pole of your potato battery.
- Use the black alligator clip connection wire to connect the black probe of the multimeter to the zinc electrode. Zinc will be the negative pole of your potato battery.
- Read the voltage on the multimeter. The pointer should move and show about 1 volt. If this does not happen, test your connections or test the multimeter to see if it can show the voltage of a AA size battery.
Experiment 2: Getting an LED to light up
Introduction: Each light bulb or electrical device requires a certain Voltage and a certain Current in order to light up or operate. (If you think of an electrical wire as a pipe carrying electrons, then Voltage is the pressure of electrons. Higher voltage can make them move faster when the circuit is connected. The Current is the amount of electrons that can move each moment. For example if the diameter of a pipe is bigger, a larger amount of electrons can pass trough and the Current can be more). The challenge in this experiment is to get the right amount of voltage and the right amount of current required for your lamp. LEDs are special types of electronic lamps that require low current, but high voltage. In order to create a higher voltage, you must connect 2 or 3 potato batteries in series. Since you don’t need high current, then the electrodes can be smaller. Some students cut their electrode in half for this experiment. Some others will just buy more electrodes.
Although LEDs do not require much current, they need a minimum voltage of about 3 volts.
Each potato battery usually creates about one volt. To get a higher voltage you will have to connect 2 or more potatoes 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.
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 potato must be as much as possible in order to get the most electric current.
Experiment 3: Getting a flashlight lamp to light up
Introduction: Each light bulb or electrical device requires a certain Voltage and a certain Current in order to light up or operate. The challenge in this experiment is to get the right amount of voltage and the right amount of current required for your lamp. Flashlight lamps are incandescent lamps with a metal filament that must heat up and produce light. Incandescent lamps require more current than LEDs. In order to create more current you must use larger electrodes, make sure that the highest possible amount of electrode is inserted in potato and you may connect 2 or 3 potato batteries in parallel. (Most students cannot get light in this method because the electrodes available in the kits are not large enough for high currents)
- Prepare two large potatoes (or two cups of potato juice)
- In each potato (or cup) insert one large copper electrode and one large zinc electrode in a way that they don’t touch each other.
- Use red alligator clip connection wires to connect the cupper electrode of one potato battery to the copper electrode of the other potato and finally to one of the contact screws of the lamp holder.
- Use black alligator clip connection wires to connect the zinc electrode of one potato battery to the zinc electrode of the other potato and finally to one of the remaining contact screw of the lamp holder.
- Screw a 1.2 volt flashlight lamp into the lamp holder to see if it lights up. Record how many seconds the light stayed on.
In order to have a chance with this project, you must maximize the surface of electrode that is in contact with potato or potato juice. Only a small portion of the electrodes must remain outside so that they can be used for connecting alligator clips.
Experiment 4: Which potato creates the most amount of electricity?
Introduction: The chemical compounds in each potato determine how fast the chemical reaction between the potato and electrodes will progress and how much electricity will be produced. For this experiment you must try to use potato juice or large potatoes so that you can control the amount of electrode surface in contact with potato. Do your experiment with 3 different types of potatoes and repeat your experiments in the same order at least 3 times.
1. Fill up a beaker or plastic cup with potato juice up to about 5 inches or 12 cm high. Mark the level of juice using a tape or marker. You must make sure that you will maintain the same level of juice in all your experiment trials.
2. Insert a copper electrode and a zinc electrode in the cup and secure them so that they will face each other, but not touch each other and they will stay vertical.
3. Use a red alligator clip connection wire to connect the copper electrode to the long leg of the LED lamp.
4. Use a black alligator clip connection wire to connect the zinc electrode to the short leg of the LED lamp.
5. Set your multimeter to read 2.5 Volt DC.
6. Directly or using an alligator clip wire connect the red (positive) probe of the multimeter to the copper electrode.
7. Directly or using an alligator clip wire connect the black (negative) probe of the multimeter to the zinc electrode.
8. Read and record the voltage. (Note that LED will not light up in this experiment).
9. Repeat this process for all potatoes or potao juices you want to compare.
10. Start from the first potato again and repeat your experiments 2 more times. Record you results in a table like this:
|Trial 1 Voltage||Trial 2 Voltage||Trial 3 Voltage||Average Voltage|
Questions and Answers:
1. Can I use a flashlight lamp instead of LED?
Yes, but then you will also need a lamp holder.
2. Why do I need to have a lamp in the circuit?
Without a load on the battery, all batteries will show the highest possible voltage. It is almost like empty trucks driving up hill. They all go fast. But when you add a heavy load to them, only the strongest will go fast and all others slow down.
3. How do I secure the electrodes?
You can insert the electrodes in a cardboard and then place them on the top of the beaker.
4. What if my multimeter does not have a setting for 2.5 Volt DC?
Then you can set it to 1 DCV or 1.5 DCV. In a closed circuit the voltage will usually be less than 1 volt.
Materials and Equipment:
Material and equipment that you need for this project are:
- Copper Electrode
- Zinc Electrode
- Multi-meter capable of measuring low voltages
- Flashlight light bulb 1.2 Volts
- Screw Base or socket for light bulb
- Alligator clips
- Board for mounting the base and the bulb (optional)
You can purchase the material locally from a hardware store or buy it online. Make electricity science kit of MiniScience.com contains all the above materials.
Results of Experiment (Observation):
Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.
In experiment 4 you must calculate the average voltage for each potato and write that in the last column of your data table.
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.
A sample result table may look like this:
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.
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.