Unpacking physics representations: Towards an appreciation of disciplinary affordance

This theoretical article problematizes the access to disciplinary knowledge that different physics representations have the possibility to provide; that is, their disciplinary affordances. It is argued that historically such access has become increasingly constrained for students as physics representations have been rationalized over time. Thus, the case is made that such rationalized representations, while powerful for communication from a disciplinary point of view, manifest as learning challenges for students. The proposal is illustrated using a vignette from a student discussion in the physics laboratory about circuit connections for an experimental investigation of the charging and discharging of a capacitor. It is concluded that in order for students to come to appreciate the disciplinary affordances of representations, more attention needs to be paid to their “unpacking.” Building on this conclusion, two questions are proposed that teachers can ask themselves in order to begin to unpack the representations that they use in their teaching. The paper ends by proposing directions for future research in this area.

Figure 1

An example of the need for different representations with different disciplinary affordances for solving a physics problem [1]. [A. Van Heuvelen, Learning to think like a physicist: A review of research-based instructional strategies, Am. J. Phys. 59, 891 (1991), (p. 892). Copyright 1991, American Association of Physics Teachers].

Figure 2

The $RC$ circuit diagram given in the laboratory exercise instruction featuring a function generator ($R_i$), the two channels of an oscilloscope, a capacitor ($C$), and a resistor ($R$). (Note that resistors are sometimes drawn as a rectangle in Swedish physics textbooks.) Of this information only the labeling of the function generator was explained in the laboratory instructions.

Figure 3

A coaxial cable with the black and red colored banana plugs on the left and the BNC connector on the right.

Figure 4

A pictorial and a diagrammatic representation of the students’ first attempt at connecting the circuit. FG refers to the function generator and OC1 and OC2 refer to the oscilloscope’s channel 1 and channel 2, respectively.

Figure 5

The T connector that was used to connect the function generator to the oscilloscope (channel 2) and to the circuit.

Figure 6

A pictorial and a diagrammatic representation of the students’ circuit after they had connected the oscilloscope’s channel 2 directly to the function generator. FG refers to the function generator and OC1 and OC2 refer to the oscilloscope’s channel 1 and channel 2, respectively. As pointed out earlier, the OC2 connections took place by default through the use of the BNC T connector (see Fig. 5).

Figure 7

A pictorial and a diagrammatic representation of the students’ circuit after it had been corrected according to the TA’s advice. Both “signal ends” of the cables were then connected to the same (equivalent) point in the circuit. FG refers to the function generator and OC1 and OC2 refer to the oscilloscope’s channel 1 and channel 2, respectively.

Figure 8

A pictorial and a diagrammatic representation of the students’ circuit after the TA’s second intervention. Both “grounding ends” of the cables were then connected to the same (equivalent) point in the circuit. FG refers to the function generator and OC1 and OC2 refer to the oscilloscope’s channel 1 and channel 2, respectively.