Teaching electric circuits with multiple batteries: A qualitative approach

We have investigated preservice science teachers’ qualitative understanding of circuits consisting of multiple batteries in single and multiple loops using a pretest and post-test method and classroom observations. We found that most students were unable to explain the effects of adding batteries in single and multiple loops, as they tended to use reasoning based on current and resistance where reasoning based on voltage is a necessity. We also found that problems such as thinking of the battery as a source of constant current resurfaced in this new context, and that answers given were inconsistent with current conservation. We describe the curriculum we developed that enables students to model circuits with multiple batteries qualitatively. Post-test results show that the majority of students were able to apply their newly developed model to make accurate predictions for complex circuits.

Figure 1

Circuits with multiple batteries in multiple loops. Standard methods can be used to solve problems with linear resistors like (a), but fail to deal with nonlinear resistors as in circuits (b) and (c).

Figure 2

Circuit diagrams used in multiple batteries in series pretest. Students are asked to rank the bulbs by brightness, and explain the reasoning behind their ranking.

Figure 3

Circuit diagrams used in multiple batteries in parallel pretest. Students are asked to rank the bulbs by brightness and the batteries by current, and explain their ranking.

Figure 4

Circuit diagram used in the multiple batteries in a single loop post-test.

Figure 5

Circuit diagrams used in the multiple batteries in multiple loops pretest. Students are asked to rank the bulbs by brightness.

Figure 6

Circuit diagrams used to develop the idea of potential. Students note the voltages across different elements and the orientation of the voltmeter leads.

Figure 7

Parallel connections (a) directly across the battery, (b) in series with another circuit element. The boxes represent any arrangement of bulbs and batteries.

Figure 8

Circuits used to highlight the similarities and differences between connecting in parallel with a bulb and battery (a) a second bulb and (b) a second battery.

Figure 9

Two circuits with multiple batteries in multiple loops used to develop the concept of potential and determine the direction of current. Circuits (a)–(c) are identical; in circuits (b) and (c), the length of the arrow indicates the magnitude of the current.

Figure 10

Circuit diagram used in a multiple batteries in multiple loops post-test.

Figure 11

Circuit diagram used in a multiple batteries in multiple loops post-test.