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In order to clarify the instability phenomena of a low current vacuum arc, characterized by noise on the current trace prior to the actual current chopping, an analysis of silver cathode spot has been made. For the analysis, cathode spot region is recognized as the collisionless space charge sheath connected with singly ionized collisional plasmas.It is proposed that a current level below that no real solution exists is unstable current and this current corresponds to the point at which a vacuum arc turns into unstable. It is found that there is no real solution when the current is below 19.4A. The physical explanation is considered that the electrons returning to the sheath region from the plasma one dominate over positive ions and, consequently, the electric field at the cathode surface is F02

Questionnaire investigation is implemented to the college students in Thailand and Japan, concerning electric and energy. As a result, students in both countries understand well that electric and energy are related each other. However, there are many students in Thailand who never saw photovoltaic generation and wind-power generation. Difference in knowledge of energy among the students of same generation is clear, by crossing the border.