Veggie Power! Making Batteries from Fruits and Vegetables
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Did you know that you can get electricity out of a potato? In this project you will learn how do build a simple battery using a variety of different fruits and vegetables - REALLY! You'll be able to figure out things like: How many lemons does it take to turn on a light bulb? Does an orange make a better battery than a potato? Can you use each segment of a grapefruit to make a super-grapefruit battery? You will also learn some of the basics of electricity and circuits: What is voltage? What is current? What is resistance? How much power can you get out of a veggie battery? Does an orange battery run out of "juice"? So, do a little produce shopping and then learn about batteries and electricity. Objective
The goal of this project is to make batteries from fruits and vegetables using metal electrodes. You will use a digital voltmeter along with resistors and other loads to determine the voltage, current, and power that your batteries can produce. Introduction
Batteries are like mini power plants that derive electrical energy from chemical reactions. You can make batteries with some pretty simple everyday materials. In general, all you need are: •two different kinds of metal to act as electrodes (though not just any kind of metals will work), •a liquid solution, called the electrolyte, which will react chemically with the metal electrodes, and •a way to conduct the electricity from the metal electrodes to something that is using the energy that the battery provides. Different kinds of batteries will have different characteristics. Some produce different voltages than others—like a flashlight battery at 1.5 volts and a car battery that is typically about 12 volts. Some can deliver a lot of current, and some will deliver less current. You'll learn more about voltage and current as you work on this project, but as you might already know, some things won't work at all unless the battery can provide a high enough voltage. Once this voltage is applied some things will draw more current from the battery than others. Current is a measure of how many electrons are flowing per second. The more electrons that flow per second (or the higher the current) the faster the battery will discharge. Also, if the item that your are trying to power with the battery tries to draw two much current then the voltage of the battery will drop and again the item might not work. Many batteries are made up of more than one battery cell, also called a voltaic cell. When these voltaic cells are hooked up in series (see Figure 1, below), the voltage of the battery becomes the sum of the voltages provided by each cell. Car batteries typically have six cells, each producing about 2 volts, which added together provides a 12-volt battery. (This is why you see six little caps on most car batteries, allowing you to add water to each of the six cells.) The battery below is made up of 4 1.5 V cells in series, producing 6 V total.
Figure 1. Pictorial (top) and schematic (bottom) diagrams of batteries connected in series. Connecting battery cells in series increases the total voltage available. The total current available remains equal to the current of a single cell. If a battery or a voltaic cell doesn't provide enough current, you can connect a number of batteries or cells together in parallel (see Figure 2 below). This keeps the total voltage the same, but now the total current that can be provided is the sum of the currents from each of the...