Make Electricity from Fruits or Chemicals
Science Project

A battery, which is actually an electric cell, is a device that produces electricity from a chemical reaction. Strictly speaking, a battery consists of two or more cells connected in series or parallel, but the term is generally used for a single cell. A cell consists of a negative electrode; a positive electrode and an electrolyte, which conducts ions.

In the year 1800 Alessandro Volta invented the voltaic pile and discovered the first practical method of generating electricity. Constructed of alternating discs of zinc and copper with pieces of cardboard soaked in brine between the metals, the voltaic pile produced electrical current. Alessandro Volta's voltaic pile was the first "wet cell battery" that produced a reliable, steady current of electricity. 

Since then varieties of batteries are made for commercial or specialized uses. Different batteries use different electrodes and different electrolytes. Some electrolytes contain corrosive or otherwise hazardous substances. 

Making batteries and producing electricity is among the most exciting and educational experiments that students can try as their school project or science project. To avoid exposure to hazardous chemicals, ScienceProject.com recommends using household materials such as saltwater, lemon juice and other fruit juices or fruits as electrolytes.

The instructions in this page is a combination of instructions published by ScienceProject.com and instructions published by MiniScience.com

Published with permission.

Light up a light bulb!

Although challenging, you can make enough electricity from fruits to light up a small light bulb. To be more precise, it's not the physical size of the light bulb that matters. You really need a light bulb that requires very low voltage and very low current.

What is voltage and what is current?

Electricity is a flow of electrons (almost like a flow of water). Voltage is the speed or pressure of electrons (like the pressure of water in a pipe or the speed of water exiting the pipe). Current is the ratio of the flow. (A river has a larger current than a narrow pipe. The total amount of passing water is a function of the current and speed.)

This project is also a good practice for learning about electric current and voltage. Some light sources require high current and low voltage while others may require high voltage and low current. The order in which you connect fruit batteries may result either higher voltage or higher current.

What materials do I need?

The materials you need for making fruit batteries and performing related experiments are:

  1. Pieces of copper sheet metal.
    Copper can easily be found in some hardware stores. You can also purchase copper electrodes from MiniScience.com or other science suppliers.
  2. Pieces of Zinc sheet metal.
    Zinc is often hard to find. Most hardware stores do not sell zinc. Zinc electrode is easily available from MiniScience.com and some other science suppliers.
  3. Low voltage light bulb.
    Small 1.2 volt light bulbs are available in some hardware stores, some dollar stores and MiniScience.com online store. 
  4. A multimeter.
    Multimeter is a device that can measure the electrical voltage, electrical current, electrical resistance and check continuity. Not all multimeters are good for this experiment. Since fruits do not produce high voltage, you need a multimeter that can measure low voltages. Do not use digital multimeters for this project. Analog multimeters are the best choices for beginners. Analog multimeters can measure voltage without having a battery inside. The best multimeter for this project is AMM360.
  5. Connecting Wires.
    Use wire leads with alligator clips in both ends for easy and quick connections.

Using a kit

You may find it to be a big saving when you buy the materials as a kit. MiniScience.com has a kit for this project called "Make Electricity Science Kit".

  Make electricity science kit contains all the materials that you need in order to successfully experiment making electricity by a chemical reaction. In addition to the kit materials you will need some fruits to complete your project. Most fruits have enough chemicals (In the form of minerals and acids dissolved in water) that can be used to produce small amounts of electricity.

Materials included in the kit are shown in the right. LED stands for Light Emitting Diode. LED is used as a low current light source.

The purpose of this science kit is to simplify the process of finding and purchasing materials that you need for your experiments.

DO NOT INSTALL BATTERIES

Analog Multimeters does NOT need battery in order to test voltage and current. You will only need to install the batteries if you need to measure the electrical resistance.

 
 Miniature Socket

 
 Copper and Zinc
electrodes

 
Multi tester or
Multi meter

 
Base board 

 
Red and Black Wire Leads

 
Screws

 
LED

 
Online Instructions

 
Miniature Bulb 1.2V
Online Stores:
Kits or materials may be ordered online at MiniScience.com or klk.com.

Some experiments in this page have used copper sulfate solution. Copper sulfate is not included in your kit, but is usually available from pool suppliers and hardware stores.

Don't Install the battery

Your multi-meter comes with a battery, however you will not need to install battery for this project. Your potato or lemon will make enough electricity for the meter to work. Set your meter to 2.5 DCV. This setting is for Direct Current Voltage measurement up to 2.5 volts.

Read the voltage on the line that reads from 0 to 250 and divide it by 100 to get the real voltage.

 Make electricity from a lemon (or potato)

This experiment will show that electricity can be made by a chemical reaction between fruits and different metals. This method is used in batteries and creates direct current (DC) electricity. Here is a sample recipe for making a fruit battery. Material that you need for this experiment are:

  1. citrus fruit 
    (lemons or limes work best)
  2. Copper electrode about 5 cm long
  3. Zinc electrode about 5 cm long
  4. One small light bulb (1.3 volts)
  5. Socket for light bulb
  6. Wires
  7. 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. Also electrodes should not touch each other.

6. Connect DC volt meter to the electrodes, it should show some voltage. If you see some voltage, connect alligator clips to the electrodes to see if you get some 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 bulb, 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.

 

 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.

Low voltage LEDs are available in electronic stores such as Radio Shack.

Although LEDs do not require much current, they need a minimum voltage of about 3 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.



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.


 We decided to repeat the first experiment with 5 small cups and smaller pieces of copper and zinc plated screw instead of zinc.

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:

  1. Felt should get wet, but it should not have any excess liquid running off the felt.
  2. You may substitute the felt with any thick, absorbent cotton fabric.
  3. Copper Sulfate is not included in your kit, but it may be purchased from hardware stores and pool chemical suppliers.
  4. As a result of this experiment, a layer of black copper oxide will be formed on the zinc as shown on the above picture.

All descriptions and pictures are copyrighted materials of ScienceProject.com and MiniScience.com and their respective organizations. Printed by permission.

This article is also available online at http://www.MiniScience.com/link