Some Simple Formulae for Grounding in a Laboratory and the Respective Definition of "Strong Current": a Gate Into Electrical Safety
The concepts of "high power" and/or "heavy current" are defined from the positions of electrical safety in a power laboratory. According to this criterion, for the nominal full power of the device under test (generator, motor, or transformer), we obtain that , where Rgr is the resistance of the grounding, is the maximal voltage permitted for touching, and is the range of the output voltage of the power device, associated with its non-ideality as a voltage source. Limiting one of the values Rgr, or Snom, for the other given, this formula defines what is "high power" for a given laboratory, and the concept of "heavy current" thus appears as a relative one, adjusted to the safety needs. This approach can be helpful in making the very important topic of electrical safety interesting for students and teachers.
Most subject teachers are not specifically educated for inclusion. Inclusive practice at classroom level remains a blind spot. This case study provides insight into the inclusive practice of two science teachers by video-based participant observation and then uses the data as a basis for professional development. The videos were recorded in an inquiry-based science class of an urban “inclusive middle school” in Austria. The two science teachers of this class reflected upon their own instruction. Three more science teachers reflected upon the others’ teaching. The focus of the study was on what the teachers noticed and reasoned as they viewed the videos. The reflective sessions were audiotaped. Grounded Theory was used to analyze and compare the data. Surprisingly, the results show that inclusion was not often addressed and it was especially difficult to discover in others’ teaching; however, implicit connections to inclusive, but not subject-specific teaching principles, can be drawn.