Turning the Wheel through the Ages

Abstract

Methods for reliably generating alternating current via placing metal coils in a rotating magnetic field were discovered by two individuals almost simultaneously: Italian engineer and physicist, Galileo Ferraris, and Austrian-American engineer, Nikola Tesla. While Tesla attained the patent for the AC-generator, Ferraris, who published the discovery a few months prior, is credited with having paved the way for the modern-day alternator, now used ubiquitously.The origins of rotational energy conversion can be traced back to sugar plantations in the 1600s. At that time, the milling process was initially sustained through slave-driven turning of a wheel, which was geared to large wooden rollers that would squeeze sugar cane. The Caribbean and South American variant of this system was known as a trapiche, which employed three geared rollers. Over time, slaves were replaced with oxen and horses, which were eventually supplanted by water wheels and finally by steam engines. The water wheels implemented for sugar milling ultimately paved the path for creating electrical currents. Water turbines for hydroelectric power subsequently took off. Principles of steam engine operation were adapted for electrical power as well, ultimately culminating in the use of nuclear plants to generate “wheel” turning for electricity.Electricity and magnetism, as well as interactions between them, are frequently discussed in introductory undergraduate physics. However, practical applications of these principles are often omitted from lectures. If taught under an experiential environment, these concepts can be introduced at even the middle school level, taught by first year college students taking basic college physics - a synergistic learning environment. With this in mind, we developed a middle school kit consisting of simple 3D-printed components, recycled DVDs and four bearings for support of 4 mm nail shafts. Enameled wire (30 AWG) is used to prepare the wire-wound coils. A large rubber band is used as the pulley-belt. The above represents the generator component. The power use component is assembled on an accompanying bread board. Power processing is demonstrated using diodes for rectification to DC. The DC power is used to recharge a 3V, 40 mAh lithium-ion coin cell. AC power from the generator can also be directly applied to load resistors. Students will be able to see the effects of varying the load by changes in the time of the free rotation of the generator wheels. Students will experience the charge and discharge of batteries with safe voltages and currents.Middle school students will record data from the generator and conditioning systems and draw conclusions on worksheets that accompany the hardware.