Keith S. Taber
Amy was a participant in the Understanding Science project.
Amy (Y10) suggested that a circuit was "a thing containing wires and components which electricity can pass through…it has to contain a battery as well". She thought that electricity could pass through "most things".
For Amy "resistance is anything which kind of provides a barrier that, which the current has to pass through, slowing down the current in a circuit", and she thought about this in terms of the analogy with water in pipes: "we've been taught the water tank and pipe running round it… just imagine the water like flowing through a pipe, and obviously like, if the pipe becomes smaller at one point, erm, the water flow has to slow down, and that's meant to represent the resistance of something".
So for Amy, charge flow was impeded by physical barriers effectively blocking its way. She made the logical association with the density of a material, on the basis that a material with densely packed particles would have limited space for the charge to flow:
So electricity would "not very easily" pass through a wooden bench "because wood is quite a dense material and the particles in it are quite closely bonded".
In air, however, the particles were "not as dense as a solid". When asked if that meant that electricity can pass through air quite easily, Amy replied: "yeah, I think so".
Amy's connection between the density of particles and the ease with which charge could flow is a logical one, but unfortunately involves a misunderstanding of how charge flows through materials, i.e., from a canonical scientific perspective, thinking about the charge flowing through gaps between particles is unhelpful here. (So this can be considered an alternative conception.) This seems to be a creative associative learning impediment, where prior learning (here, the spacing of quanticles in different materials) is applied, but in a context beyond its range of application.
