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Make Electricity from Fruit Science Project, Part 1

Courtesy of MiniScience.com Part 2 of the article available here

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.

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.” This 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.

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 the 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.

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 shine.)
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 amounts 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 in more electricity. Since the produced electricity is so little, you have little chance of 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.

The instructions for this project are a combination of instructions published by ScienceProject.com and instructions published by MiniScience.com. Published with permission.■