Tech Directions - October 2007 - (Page 13)

Rock Your Classroom! Use Subwoofers to Teach Electricity and Science By Robert J. Karns rkarns@alleganaesa.org I T doesn’t seem like school is the best place to crank up the bass for glass-crackin’ extreme energy, but subwoofers just may make better teaching and learning tools than they do music makers. Faced with the fact that electricity is invisible, electrical technology students encounter significant challenges in the classroom when abstract concepts and principles get introduced to illustrate the behavior of electricity. What can help? Subwoofers to the rescue! without the presence of good examples. But an electro-dynamic machine that can deliver 160 decibels of raw sound power quickly captures a student’s attention—and goes on to serve as a platform from which instructors can launch many lessons in electricity. Imagine having a device in the classroom that has a reputation of handling 1,000 W of RMS power—and that can deliver important curriculum goals found in State Board of Education frameworks. The subwoofer is the answer. The Challenge and the Solution Consider for example, the vector representations often used in textbooks or on classroom white boards to depict magnitude and timing relationships between voltage and current in electrically reactive systems. These drawings may be accurate in terms of what they represent, but too often they fall short of getting the message across while getting students involved. Even the most appealing approaches used to relate electrical theory, like Pythagorean’s theorem, may still seem meaningless to many students Robert J. Karns is electromechanical instructor, Allegan (MI) County Area Technical and Education Center. Subwoofer Background Technically classified a movingcoil electromechanical transducer, a subwoofer is commonly called a "driver." It can be shown in its analogous electrical impedance circuit equivalent form as parallel resistance, inductance, and capacitance (RLC). Thanks to scientists like F. H. Olson, scientific thinking paved the way to the electrical model equivalent of today’s loudspeakers. Since Olson’s discoveries, dozens of noteworthy scientists, like Beranek, Novak, Thiele, Benson, and Small, have spent innumerable hours contributing to advanced levels of understanding in loudspeaker theory. Their work and that of others has transformed loudspeaker design and development into more of a science and less of an art, ultimately leading to extremely accurate prediction and performance of loudspeaker behavior in a wide variety of environments. Typically, a set of electromechanical parameters is either available or generated for each electromechanical driver, referred to as T/S (Thiele/ Small) parameters, so that using this data ensures accurate alignment of each respective driver to its ideal enclosure type. Aligning each driver to its ideal companion enclosure allows it to achieve optimal performance as a sound-wave maker. Waves to Waves An electrical, mechanical, and acoustical apparatus, the subwoofer has a rich ability to serve as a primary teaching tool. The most obvious concepts of resonance and equilibrium are easily extracted from loudspeaker behavior and related to students through active, soundintensive demonstrations. The moving diaphragms pique student interest and set the stage for additional lessons in basic electricity, as well as more content delivery in the areas of science and physics. Examining sinusoidal patterns of motion in this mechanically resonant (Fig. 1) system introduces students to www.techdirections.com ELECTRICITY/ELECTRONICS 13 http://www.techdirections.com

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Tech Directions - October 2007 Technically Speaking Contents Direct from Washington The News Report Technology Today Technology’s Past Mastering Computers Rock Your Classroom!—Use Subwoofers to Teach Electricity and Science Sure, They Can Build It, But. . . . Manufacturing Students Need Process Planning Skills Teach Graphic Design Basics with PowerPoint Free Teacher Resources Product Central More than Fun

Tech Directions - October 2007

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