model for the electric field. This paper describes how the Lycra® sheet might be implemented in the curriculum for an introductory physics class. Background Student Beliefs Traditional Instruction LSFM Instruction Boundary Model - The effects of gravity diminish rapidly or disappear completely, no gravity in space (Williamson & Willoughby, 2012). Gravity is the result of other forces (i.e. magnetism, rotation, or atmospheric pressure) (Watts, 1982). The of gravity acts through a medium (Watts,1982; Williamson & Willoughby, 2012 ). The gravitational force is selective in how/when it is applied (Watts, 1982). Inconsistent in the way they apply their beliefs about gravity (Palmer, 2001). The traditional approach “does not take into account the students’ initial conceptions, are often incompatible with scientific knowledge” (Baldy, 2007). Historical approach starting with Kepler’s Laws and then proceeds to discuss Newton’s use of laws, which are based on observation, to derive whereas the conceptual relationships are generally stated. Textbooks seldom devote a whole chapter to gravitation. Gravitation is often with the chapter on uniform circular motion. Students memorize the formula, remembering and reciting it, but lack conceptual understanding of the physical phenomenon. The Lycra® Sheet Field Model agrees with modern, relativistic theory. The use of a physical model to represent the gravitational field enables the student to make personal prediction and observations about the nature of the field. Demonstrations show that the field is not a localized phenomenon, Students determine that gravitational force has infinite range. Demonstrations show the interactions of gravitational fields causing objects to attract to one another. Objects orbiting a massive object can be demonstrated the Lycra® Sheet Field Model. Abstract electrostatic concepts are difficult for students to assimilate and understand (Arons, 1997). Students have little conceptual experience with electrostatic phenomena. Students’ experience of static electricity comes from Often taught after mechanics topics and most students do not see a connection between the topics. Demonstrations of charging processes and the interaction between charged objects. The relationship between charged objects is generally The gravitational – electric force/field analogy develops naturally. Each concept has already been introduced in terms of the gravitational field, and the difficulties the students generally have with the nature of the electric field dissipates.
observations of static cling, static electric shock, charging a rubber balloon by rubbing it against their hair, etc. Young children are told by their parents that “opposites attract” without being given any explanations. Students learning about electrostatic phenomenon are able to use terms such as “electric charge,” “like charges,” “unlike charges,” “electric current,” “potential difference,” etc., but cannot give concrete meanings to describe the words as they use them. Students will often attribute the electric force interactions to another force, like gravitational or magnetic. given to the students and, like gravitation, many times does not include a physical model demonstrating the reasons for the interaction. The Coulomb’s Law equation is generally stated, followed by the analogy to Newton’s law of gravitation and comparing the relative strength of the respective forces. The abstract and foreign concepts that students typically struggle with do not affect student learning. Instruction with the Lycra® Sheet Field Model to teach electrical concepts becomes a spiraling activity and an opportunity to review concepts. Students observe that the interaction between objects that are charged does not require physical contact in order for the force to be applied. Students are able to independently recognize the similarity to gravitational attraction. They should notice that the closer the charged objects are, the greater the electric force is acting between the charged objects. This observation may remind them of the gravitational field relationship. At this point, students can return to the Lycra® Sheet to review the gravitational field concepts. The Lycra® Sheet Field Model The Lycra® Sheet Field Model is introduced as a physical model of gravity that is patterned after Einstein’s theory of the space-time fabric. The Lycra® sheet can be purchased at any fabric store. It is recommended that the fabric contain about 20% spandex, which gives it a considerable amount of stretchiness. The sheet should be large enough to be easily manipulated and visible to the whole class; a 4.5’ x 4.5’ sheet is a good size to meet these requirements. The