Lemon Battery - a simple elctrical project for school college students

Lemon Battery

The lemon battery is a simple type of electrical battery that is commonly made for school science projects because it illustrates a battery's main components. Typically, a piece of zinc metal and a piece of copper metal are inserted into a lemon. Everyday objects such as galvanized nails and copper pennies can be used for the zinc and for the copper. A single lemon is usually studied using an electrical meter. Several lemons can be wired together to form a more powerful battery that will power a light-emitting diode, a buzzer, or a digital clock.

The lemon battery is similar to the first electrical battery invented in 1800 by Alessandro Volta in Italy. Volta used brine (salt water) instead of lemon juice. The lemon battery is described in some textbooks in order to illustrate the chemical reactions that occur in batteries. The zinc and copper are called the electrodes of the battery, and the juice inside the lemon is called the electrolyte. There are many variations of the lemon battery that use different fruits (or liquids) as electrolytes and metals other than zinc and copper as electrodes.

This article contains instructions for making a lemon battery and using it to power a light-emitting diode. If you want to know more about the science and history of the lemon battery, you can get started  Wikipedia.

Materials and equipment required:

• Light emitting diode. These look like plastic pieces with 2 wires stuck into them. They are usually just called LEDs, which comes from the first letters of the three words Light Emitting Diode. When the right battery is hooked up, the LED will glow. A red one is good for the lemon battery experiment; there is another section of this article that discusses how to find an LED. While LEDs are a good choice for this experiment, some other ideas are given below in the section "Alternative devices".
• Lemons. You'll need 3 or 4. Any citrus fruit, like limes, grapefruits, or oranges, or even a potato will work.
• Zinc electrodes. You'll need 3 or 4. Most likely you'll use a piece of metal that's been coated with zinc. This is what the word "galvanized" means. A galvanized metal washer that's about one inch (2 – 3 cm) in diameter will work well. Galvanized roofing nails, galvanized screws and bolts, and even paper clips can also work. If you can find some zinc sheet, and some shears or tough scissors to cut it, that will work very well. Be careful if you do this; the edges of sheared metal sheets are sharp. If you can, file the edges to make them less sharp.
• Copper electrodes. You'll need 3 or 4. Copper or copper-coated pennies work well. You may find some good copper fittings in the plumbing section of a hardware store. Again, if you can find some copper sheet, and some shears or scissors to cut it, that will work. Again, be careful about sharp edges.
• Leads. You'll need 5 or 6. The easiest thing is to get hold of a packet of insulated lead wires with "alligator clips" on each end.
• Multimeter (optional). If you know how to use an electrical multimeter, it can be helpful in getting your battery to work.

Making a single lemon cell

Make the first lemon cell. Your battery is going to have at least 3 lemon cells, but each cell is made the same way.

1. Clean your electrodes carefully. Your goal is to get any dirt or grease off of them, and also to scrub away the thin "oxide" coatings on them. It should work fine if you clean them in the same way that you'd clean a pan in the kitchen to make it clean and shiny. Scrubbing with steel wool or with an abrasive sponge will work fine; if you are using a galvanized electrode, be careful not to rub off the zinc coating completely.
2. Stick one zinc electrode into the lemon (or other fruit). You may need to use a small knife to cut a slit into the lemon. You want the electrode to go into the lemon as deeply as possible, but you'll need a little bit of the electrode to stick out of the fruit so you can attach a lead wire to it. Wiggle the electrode around a little to smash the membranes inside the fruit.
3. Next, stick the copper electrode into the same lemon. You want this electrode to be close to the zinc electrode, but it must not touch the zinc inside the lemon. If they do touch, your cell will not work. As for the zinc electrode, you want to stick the copper electrode into the fruit as far as you can, and you want to wiggle it a bit to make sure the membranes near the electrode are broken.(Optional) If you are using a multimeter, you can do the following tests to make sure your lemon cell is working.
4. Hook up two alligator clips from your leads to the two electrodes. Connect the two clips to the leads of the multimeter.
5. Measure the voltage from your lemon cell. It should read about 0.9 - 1.0 volts.
6. Measure the current from your cell. You should read a few tenths of a milliampere. Some multimeters are not sensitive enough to measure currents less than one milliampere, in which case you'll just see 0.0 as the reading.

Making the lemon battery

When several lemon cells are wired together, the collection is called a battery. We usually call a single lemon cell a battery also. Most batteries that you may purchase to use in toys and electronics have just one cell inside.

1. You need to make 3 lemon cells. If you're using a multimeter, make sure that each cell generates the correct voltage and the correct current.
2. Using two lead wires, connect the three cells together. Connect the zinc electrode on the first cell to the copper electrode on the second. Connect the zinc electrode on the second cell to the copper electrode on the third lemon. This is called a "series" connection; the three cells make up the lemon battery.

Connecting the LED

Connect a lead wire from the copper electrode of the first lemon cell to the longer lead wire from the LED. Connect a lead wire from the zinc electrode of the third cell to the shorter wire of the LED. You may need to gently pull the lead wires that come from the LED apart; the alligator clips on the ends of the two lead wires that connect your battery to the LED must not touch each other.
The LED will glow now enjoy your diy project.

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