Who knew that fruit could generate power? A battery created from a simple, everyday lemon illustrates quite well how electricity works. The lemon battery is a favorite of science fair participants since it is easy and fun to replicate. All you need is a lemon or two, and a few common household objects.
To create your battery, you will need one lemon, galvanized nails (they must be galvanized, because galvanized items have zinc in them, and zinc is very important to this experiment), copper wire, an LED bulb (such as those found in Christmas lights), miniature jumper cables and a multimeter to measure the voltage.
To create the battery, roll the lemon around and squeeze it gently to release the juice inside. Next, take a nail and stick it about two inches into the lemon. Take a piece of the copper wire and stick it two inches into the lemon, making sure it doesn't touch the nail.
That's it! You now have a lemon-cell battery. Now let's experiment and see what it can do.
If you connect the multimeter to the lemon cell, you will see that the lemon is indeed giving off a charge. But is it enough to power the LED light? As you can see on the multimeter, a single lemon cell gives off about .9 volts (See Reference 1). LED lights require 1.5 to 4 volts of electricity to light up, depending on the color (See Reference 2).
So to create more power, create another lemon cell in the same way you created the first one. Now look closely at the prongs of the LED light. Connect the negative jumper cable to the flat prong, and the positive jumper cable to the rounded prong. Make sure that they are connected properly, otherwise it won't work. Attach the positive lead of one lemon to the negative lead of the next. Now attach the LED light, and you should get a faint light. If you add a third lemon to the battery, it will glow even brighter.
How it Works
When you insert the copper wire and galvanized nail into the lemon, they act as positive and negative leads. The copper wire transfers electrodes to the nail, using the lemon's citric acid as its electrolyte. The electrolyte is the highway on which the electrodes travel, so to speak. Because the nail is the receiver of the electrodes, it acts as the negative lead and the copper wire is the positive.
Powering the Light
If you connect the open ends of the leads with a cable, you get electrodes traveling around in a circle; from the copper to the nail, up the nail, through the cable, down the copper, and so forth. This flow of energy is called a short circuit. If you replace the jumper cable with the LED light, it acts as a load and draws power from the lemon. If you add another lemon cell, the voltage increases.
Lemons may not be the answer to the world's energy woes, but when used correctly, they can aptly demonstrate working electricity in a safe and interesting manner.