A New Model Course in Applied Quantum Physics E.F. Redish, R.N. Steinberg, M.C. Wittmann Home | Overview | How Students Learn | Classroom materials | Teacher's Guide

Students listening to Students An integral part of the course is students learning to listen to others and to hear what others are saying. In the example below, Mark (aliases used throughout) clearly describes his model of electron flow. He presents two different ideas. The students seem to agree with one but not necessarily with the other (though this is cut off at the end due to time limitations). This discussion happened 45 minutes into a 50 minute class period. Video | Transcript | Commentary To view the video samples below, click on the images. QuickTime is necessary for viewing the videos. Return to Teacher's Guide.

The question: how do we describe electrons moving through a circuit?

Summary: One student, Mark, clearly states his point of view, while the others listen and comment on (think along with) his ideas. Mark clearly presents two ideas: in a resistor, an electron is free to move about, but in a conductor, an electron moves from bound to bound state. Mark's comments on electrons in conductors are consistent with research results on student beliefs that current is the movement of electrons from one bound state of an atom to another. For more details on this research, click here.

Transcript: Mark: Well, quantum mechanically, if that's the case, if an electron enters a resistor, if it's not bound, then it is bumping into things. Fay: (note her hands moving around, showing an object bumping around in space). Mark: But it's being pushed through by the electric field. Fay: Yes! Mark: If it is bound, it's not going anywhere. Fay: Exactly! But, since it came in, then it can't be bound, because all the bound ones are there. Mark: Right, right. Whereas in the conductor it is entering bound states, but these are loosely bound states, that's a difference. Fay: Yeah, or otherwise you can think of it as, you've got these - the dudes in the wire and they all have their electrons, right? all around them... Mark: Right Fay: ...and you're just going to have an electron that goes whoosh de whoosh de whoosh (note her hand movement on the paper, this time presenting to the others the same hand motion she had done only for herself earlier). Mark: So, in the resistor, we're looking at essentially unbound electron (nets?) going through physical obstacles. When I say physical, I mean mechanical obstacles, as opposed to quantum mechanical? Jeff: Yech! (for the bad pun) Mark: On the other hand, in the conductor, it's going from one bound state to another. Jeff: yeah, it's kinda like the whole, ... Mark: but loosely bound state! Jeff: This is what I was thinking earlier... Commentary: Though many issues can be discussed based on this video clip, we emphasize four: Student respect for others Note how all the students in the group listen to Mark and respond to his comments. They respect his voice and think along with him. Though two students go on to disagree with Mark on his second point, the discussion is one in which the students try to help each other develop an appropriate understanding of the physics. This emphasizes the observation we have made that students often learn well by listening to each other and struggling with ideas for an extended time. Thinking along, sharing ideas Note how Fay first thinks along with Mark's comments, then shares these ideas with the other group members. At first, she's waving her hands in the air (matching the pattern of the electron bouncing between physical obstructions in the lattice). Then, she describes the to the whole group about the "dudes in the wire" (lattice atoms) and how the electrons move, being sure to include a diagram that all can see. The very physical nature of her description (complete with sound effects) indicates that she has internalized the ideas and made a personal description of the situation, though her language does not indicate how well, nor how she would apply these ideas in another setting. Moving toward a discussion Though the video ends (due to an interruption, the following discussion is difficult to present coherently), the clip shows how the students are beginning to disagree. Though Jeff seems to agree ("yeah, it's kinda like..."), he ends up changing his mind ("This is what I was thinking earlier..."). At this point, he has grabbed the group's attention, but goes on to state that Mark's resistor model holds even in the case of the conductor. Student reasoning about the physics Mark's model of electron motion in conductors has been studied in detail by the Physics Education Research Group at the University of Maryland. His model is not unique, and shares elements with models proposed by many other students both in written exams and individual demonstration interviews. For more information on the types of reasoning students use in our classroom, click here. Return to Teacher's Guide.

 

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