The concept of voltage is difficult for students to understand. The main reason of its difficulty might be attributed to the fact that the concept of voltage indicating a behavior of charged particle (electron) is not shown in the learning process of voltage. In this study we intend to work out "a model of density. of electric charge" which illustrates how electron composes voltage, using charging small balls made of formed polystyrene as the model of electron. With this "a model of density of electric charge", we were able to carry out the experiment that achieves the following purposes. (1) To show students the interaction between electrons by changing the density of electron. (2) To show them the influence of the density of electron on Coulomb force. (3) To show them the influence of the density of electron on electronic field. To clarify the effects of the model described above, we tried two demonstration lessons using this model. The result showed that "a model of density of electric charge" was effective on the development of the concept of voltage for students.

The purpose of this study is to clarify the actual conditions and structure of the learner's academic motivations in science education of an elementary and secondary school. Another purpose of this paper is to measure and analyze the developmental variations of their self-efficacy and the condition of metacognitive strategy, and their relatedness to the circumference at learning science in education of Japanease elementary school scenes (grade 5 and 6), lower secondary school ones (grade 8), and upper secondary school ones (grade 10), with using the SESSE (Self-Efficacy Scale for Science Education) and the MSCS (Metacognition Scale of Cognitive Strategy). The findings of this study are as follows: 1. The learner’s self-efficacy and the ability of cognitive strategy in science learning gradually decline as their grades advance to the upper secondary school level from the elementary school level. 2. The data of these scales in this study showed the decline of learner’s learning motivation and eagerness in science at the stages between 6 grade and 8 grade because the mean scores of their Control and Agency Beliefs for effort, ability, self-appraisal and self management of the metacognitive strategies, and the importance of teachers and their roles in learning stuations of junior high school students (grade 8) paticularly indicate lower, compared with those of elementary school ones (grade 6). The significant differences between these grades might mean a disincentive on learning science. 3. As there are relatively strong correlations between the scores of their cognitive strategies and Control and Agency beliefs for effort, ability, and are also moderate correlations between the scores of importance of teachers and their roles in learning stuations and those beliefs, so the ability of cognitive strategy and teachers’ roles can be regarded as one of the principal conceptions which compose the learner's self-efficacy in science learning. These results will give us an opportunity to modify many old conceptions related to an extrinsic and intrinsic motivation we have already had. As a result, there might be a several possibilities of developing a new theory of academic motivation for science education.