School Projects on Voltaic Piles
From laptop power packs to the ubiquitous AA batteries, portable electricity relies on the noble battery, which traces its history all the way back to experiments in electricity conducted around the turn of the nineteenth century by Alessandro Volta. His "voltaic piles" were early predecessors of the modern battery, and science projects based on Volta's experiments --- or the work of those who came after him --- can be a good way to introduce basic concepts of electricity.
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Constructing a Simple Voltaic Pile
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Alessandro Volta discovered that when copper and zinc are connected with a conducting liquid, a wire that connects the two will register a voltage. You can replicate Volta's original experiments by using a zinc electrode and a copper electrode. The two electrodes should be submerged in a bath of saltwater or something acidic like lemon juice. If you have a voltage meter, turn it down to its most sensitive DC setting --- generally 10 volts or less. Connect the negative probe to the zinc electrode and the positive probe to the copper electrode. The needle on the voltage meter will move to indicate the voltage that is being generated by the voltaic pile.
Recreating Volta's Battery
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Volta's battery was much more complex than the voltaic pile. You can recreate it by using thin plates of copper and zinc in equal number. Alternate the plates of copper and zinc, separating them with layers of cardboard. When you run out of plates, wrap a line of electrical tape around the contraption to bind it together and then dunk it in salty water until the cardboard becomes soaked. Take two pieces of wire and connect one to each end carefully. If you measure the voltage by touching the wires to the probes of a voltmeter, you can see that this battery generates much more power than one using only two electrodes. You can then perform simple nineteenth-century experiments, such as immersing the ends of the wires in saltwater --- the bubbles that form are hydrogen and oxygen created as the water molecules are split by the electricity.
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Explain the Evolution of Batteries
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Alessandro Volta's voltaic piles weren't the first "batteries": Leyden jars, which stored static electricity, came before them --- and some have argued that jars discovered in Iraq show that ancient civilizations had created batteries of their own thousands of years ago. The voltaic pile, however, led directly to modern dry cell batteries still used today. A school project can show how voltaic piles, which use a liquid conductor that could easily slosh over the battery (or evaporate), incrementally evolved into the dry cells used in your flashlight. Research the work of John Daniell and explain why his battery, which used copper sulfate and zinc sulfate instead of a simple electrolyte, was longer lasting and more efficient than Volta's original piles. Then, illustrate how Georges Leclanché took this one step further by using a dry paste instead of an unwieldy liquid to create the "dry cell" --- the type of battery still used today.
Show How Voltaic Piles Work in Series
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Constructing multiple voltaic piles and connecting them together can show how the power of a circuit is increased by connecting the batteries "in a series," or one after another. A school project can demonstrate how many simple voltaic piles it would take to light up a light bulb or power a laptop computer by adding up the voltage generated by each pile. You can also show how this principle is at work even in what we think of as single batteries: To do this, peel the label off of a six-volt lantern battery and use a hobby knife to cut through the plastic case to remove the top of the battery. Inside you'll discover four smaller D cell or F cell batteries hidden within each a 1.5 volt cell. When the four are added together in series, they generate six volts (four times 1.5).
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References
- The University of Arizona Chemistry: Making a Copper-Zinc Battery
- Kenyon College: The Electrochemical Cell
- Florida State University: Alessandro Volta (1745--1827)
- Case Western Reserve University: Electrochemistry Encyclopedia: Nonrechargeable Batteries
- Sacramento State University: Basic Chemical Production of Electricity
- Photo Credit battery image by Aditia Patria Warman from Fotolia.com
