Students are given a history of electricity and its development into the modern age lifeline upon which we so depend. The methods of power generation are introduced, and further discussion of each technology's pros and cons follows.

Understanding energy issues is an important part of engineering. The lesson and associated activity also develop the ability to explain technological concepts in simple terms. Power Energy Electricity Nuclear Solar Windmill Hydroelectric Coal Photovoltaic none Students will be able to describe important discoveries leading to electricity. Students will be able to name the different sources of power generation and how they work. Students will be able to list the pro's and con's of each method of power generation. A 15-minute demonstration to the class with anything electronic (preferably involving sparks, noise, or moving parts) can get students geared up for this lesson. Many demonstrations and explanations are available at Society for Amateur Science's webpage, http://www.amasci.com/scied.html. Because different schools have different resources available, a specific activity is not outlined here. Be sure to verify the safety of an experiment from the web before performing it around students. Key points in the history of electricity are listed below. They are not necessary for understanding of the lesson but serve as a historical background for the teacher. The majority of the information below is from Encyclopedia.com, linked below, with general knowledge added where pertinent. As early as 600 BC it was known that amber could be charged by rubbing it with a cloth. William Gilbert, the father of modern electricity, observed this process on many substances around 1600. Otto von Guericke invented in 1660 a machine that could generate static electricity. Robert Boyle recognized that attraction and repulsion were related, which contributed to C.F. Du Fay recognizing two types of charge, later named positive and negative by Benjamin Franklin and Ebenezer Kinnersley. Stephen Gray recognized conductors and nonconductors as the two types of materials known to exist at the time in 1729. Pieter van Musschenbroek invented an early form of capacitor which could store and discharge electricity, leading William Watson to discover current and the modern circuit in 1747 Henry Cavendish began measuring conductivity (how easily electricity flows through a material) and Charles Coulomb came up with mathematical expressions relating force and charge - a fact not always appreciated by introductory physics students Luigi Galvani in 1786 observed a relationship between muscle tissue and electricity and the exciting field of electrobiology was born. Alessandro Volta invented the battery shortly after · In 1827 and 1841 respectively, G.S. Ohm and J.P. Joule came up with their laws, and soon after Kirchoff contributed his as well. These laws allow for quantitative analysis of electric circuits. James Maxwell came up with his famous equations describing electromagnetic fields in 1873 and Heinrich Hertz proved them Andre Ampere gave mathematical form to Oersted's discovery that currents in a wire create a magnetic field. Michael Faraday and Joseph Henry independently developed the generator. Key concepts on power generation methods are as follows Electricity is a naturally occurring phenomena. The majority of power generating systems involve mechanical power being converted into electrical power through the use of turbines (they work like a motor, only backwards). These turbines can be driven by any moving fluid, however most operate as heat engines driven by steam. Steam can be produced in a variety of ways; nuclear, geothermal, and fossil fuels have been used. Coal plants produce the vast majority of power in the United States. These power plants operate on the flow of water from man made or naturally occurring bodies. Gravity provides the energy source that causes water to move downstream or through a dam. Turbines transfer this into a power output when their rotors are turned by the flow. They are highly efficient (~80%) and utilize an abundant renewable resource. Require a body of water and altitude gradient. Pose serious environmental threats because they Disrupt flooding cycles needed to deposit rich nutrients on surrounding land Prevent spawning of many species of fish Flood large plots of land - destroying valuable habitats and even entire ecosystems Are not permanent - reservoirs silt up over time Geothermal sources of steam exist that can power turbines, but are location specific and require geothermally active sites Efficiencies of up to 80% can be reached using mechanical power to generate electrical power. Most losses occur due to heat loss from friction in turbines, and also from direct heat transfer out of imperfectly insulated systems. The laws of thermodynamics dictate the maximum efficiency possible for a system. Simply stated, they are as follows: Matter and energy are always conserved. This means that there is a finite amount of energy in the universe. Energy can neither be created, nor destroyed. After an energy transformatoin, a system cannot return to its original energy state because there is always an increase in disorder. In other words, entropy always increases. Efficiency is further limited by heat limits and safety concerns. Most steam plants operate at efficiencies of around 40%, Nuclear at 30%. Environmental concerns are very important with such power plants. Huge problems arise from combustion of fossil fuels because of their harmful byproducts that get released into the environment. Methods exist to reduce the amount of pollution that gets into the air, but they are expensive to implement. Nuclear power leaves us with fission byproducts, which remain highly dangerous for millions of years and must be stored somewhere. Improper control of fission reactors can lead to meltdown, a disastrous situation that causes the reactor fuel to melt into the earth, releasing massive amounts of pressure, heat, and radioactive material that could affect millions - extensive regulation exists along with numerous safeties to prevent this from ever happening. They arouse in part out of two near meltdowns that occurred at Three Mile Island and Chernobyl. There is a huge amount of heat that has to be released into the environment regardless of how it is generated - this often ends up in streams or lakes, destroying fragile ecosystems. Fuel Cells Convert chemical power of hydrogen and some other substances directly into electrical power. Require production of hydrogen by some other means. Hydrogen can be stored and distributed much like oil and gasoline as a fuel source, but is more environmentally friendly in the event of a release. The technology is currently very expensive due to requirement of platinum as a catalyst in the process. Are highly efficient, 50-60 % currently, however theoretically this could reach values much closer to 100%. The byproduct of this process is water, and nothing is consumed. Photovoltaic cells directly convert light radiation to electrical power. Solar power is a renewable resource. They are real-time sources in that they cannot store energy. They are clean, quiet, and give off no harmful byproducts. Require presence of sunlight, thus they are not ideal in places where the days are very short for much of the year, though often no other options exist in such places. Panels are expensive, and have a broad range of efficiencies up to about 30% (typically 10-15%) depending on the type of panel. Clean and efficient renewable power source. Require presence of wind, often placed on ridgelines to accomplish this. Must be maintained to reduce noise pollution. Are often perceived as an eyesore Measurement of ability of a system to do work Measure of amount of energy being used or generated per unit of time (energy/time) Abundant resource that is not consumed during the process of power generation Device that produces electricity through the action of fast moving liquid, steam, or gas. Device that directly transforms hydrogen gas and oxygen into water and electricity Element that causes a chemical reaction to begin; in a fuel cell it is usually platinum Device that directly transforms light radiation into electricity Win that Bid! Selling Your Power Solution Although electricity's existence has been known for thousands of years, it has not been until the last two centuries that we have begun to understand its true nature. Only in the last century have we been able to harness electrical power for general use. Original coal and oil-fueled steam turbines release harmful hydrocarbons and other substances into the environment but provide a cheap energy source. Hydroelectric plants provide a cleaner source of power, but their negative effects have made them unpopular in recent years. Nuclear power originally promised to provide an inexhaustible source of power, but lost popularity in the late 70's, when among other things, the very close to home Three Mile Island in Harrisburg, PA had a near disastrous meltdown due to negligence - The 1986 meltdown at Chernobyl increased public fears immensely. Solar power used in conjunction with fuel cell technologies provide us with hope for the future, however high initial costs have made them somewhat slow to take off. Divide the class into teams and play a fact game on electricity and power. The winning team gets a prize - make sure they know about this beforehand. Popcorn Questions to students while presenting the information to them to make sure they are on their toes. Have students investigate and describe areas of cutting edge power source and power supply research. Physics Demos & Science Exhibit Designs Physics Demos & Science Exhibit Designs, http://www.amasci.com/scied.html, 06-22-04 Physics Demos & Science Exhibit Designs History of Electricity History of Electricity, HighBeam Encyclopedia, http://www.encyclopedia.com/html/section/electity_historyofelectricity.asp, 06-22-04 Electricity Sources of Electrical Energy Sources of Electrical Energy, HighBeam Encyclopedia, http://www.encyclopedia.com/html/section/power-el_ SourcesofElectricalEnergy.asp, 06-22-04 Electric Power What is a simple defintion of the laws of thermodynamics? What is a simple defintion of the laws of thermodynamics?, http://www.physlink.com/Education/AskExperts/ae280.cfm, 06-22-04 What is a simple defintion of the laws of thermodynamics?