Hidden circuits and argumentation

The subject matter of school physics can rarely be used to explain the functioning of devices routinely employed in everyday life, despite the even greater prevalence of technological aids in today's society. DC circuits form an exception; devices such as flashlights can be understood with the aid of DC circuits, and it can be argued that pupils should learn the basics of DC circuits in order to understand their surroundings better, and also for safety reasons.

Explaining the behaviour of simple DC circuits requires understanding of the following pieces of knowledge: components have two terminals, the ideas of closed and short circuits, Ohm's law, Kirchoff's junction and loop laws, series and parallel connections, and power and energy [1]. Whilst explaining the behaviour of DC circuits, these pieces should to be utilised concurrently rather than sequentially. Thus, understanding DC circuits profoundly requires holistic or systemic evaluation; a change made in one position can change the behaviour of the circuit at various places [2, 3]. However, this kind of thinking has been shown to be problematic as pupils often tend to evaluate DC circuits locally [2, 3]. For example, in the case of multiple resistors they might be able to determine the voltage drop caused by a single resistor, without understanding its impact to the total current going through a battery.

In order to help pupils ito develop holistic understanding of DC circuits, we present a flexible teaching method for lower secondary level¹. The core of this method lies on tasks labelled as hidden circuits. The essential idea underlying these is in hiding the actual wiring of a circuit and getting pupils to ponder the connections enabling the behaviour of the circuit. Hidden circuits have some similarities with electric circuit puzzles [4] and black box circuits [5] but hidden circuits take their ideas further while adding elements from physics education research and argumentation. Hidden circuits aim to provide research-based classroom activities that improve pupils' understanding of physics and their argumentation skills.

The hidden circuits are designed to increase pupils' understanding of DC circuits and to support the development of pupils' argumentation skills. The ideas underlying these goals are discussed in the following sections.

Difficulties in learning DC circuits

Argumentation skills

The idea underlying hidden circuits is to permit pupils to observe the behaviour of a DC circuit without seeing its wiring. The behaviour of circuits can be demonstrated with the aid of videos or by showing real circuits. One example task is presented in figure 1. Figure 1(a) demonstrates how the circuit behaves when wires are connected to the battery, and figure 1(b) demonstrates the changes occurring when the switch is closed. After observations, pupils are asked to figure out the circuit diagram that would explain the behaviour of a DC circuit (see figure 1(c)). Since the underlying idea of hidden circuits is to enhance pupils' holistic understanding, answer options are designed to address difficulties that pupils often encounter in the process of learning DC circuits. For example, options A, D, and E address the problem of not understanding the meaning of a closed circuit, C addresses the problem in distinguishing a closed circuit from a short circuit, whilst B is the corresponding diagram for the actual circuit.

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Pupils are also asked to explain their reasoning and to specify why other diagrams cannot explain the functionality of the circuit. These questions have two purposes:

• 1.  
  They provide further insight about pupils' understanding of the basics of DC circuits for a teacher.
• 2.  
  They create a foundation for teaching the argumentation skills in the context of DC circuits.

In the following sections, we describe how to utilise hidden circuits in assessing pupils' learning and in supporting their argumentation skills.

Hidden circuits enable testing pupils' abilities to apply their knowledge concerning DC circuits. The behaviour of hidden circuits can be demonstrated by showing videos, so they can be used in a regular classroom. Regarding the practical implementation of assessing pupils' understanding, both paper-and-pencil and electronic versions are possible.

With respect to the timing of assessing pupils' understanding, a natural moment to use the hidden circuits is after the essentials of DC circuits have been covered during teaching, as also recommended by our co-operating teachers. This way pupils should have the necessary content knowledge to manage the tasks. After that hidden circuits can be used to provide opportunities for pupils to apply their understanding to real DC circuits.

The hidden circuit tasks can reveal whether pupils' learning is hindered by difficulties earlier reported in literature. With the aid of these tasks, a teacher can become aware of if the pupils face these difficulties, and address teaching to these so that pupils can overcome them.

Another way to utilise hidden circuits in collaborative learning environments is to utilise an argumentation sheet that is designed to support pupils' argumentation skills [17]. The argumentation sheet helps pupils to construct an argument by describing its main elements. Besides this, the argumentation sheet prepares pupils to defend their argument from counter-arguments.

Figure 2 presents the argumentation sheet² used with hidden circuits. Pupils fill the sheet in small groups. Each group should have some pupils disagreeing about the correct answer. This should engage group members into the process of argumentation.

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Before pupils fill the sheet, the meanings for the terms to claim, observation, warrant, counter- argument, and rebuttal should be introduced. Then, a hidden circuit task can be presented to the pupils. They are first asked to think about the task on their own, and then to discuss their answers with their group members. After pupils agree on the correct answer, they fill the argumentation sheet. According to our co-operating teachers, pupils often need support in differentiating observations from warrants and in stating a counter-argument. The sheet engages pupils in applying their knowledge and sharing it to their group members. This enables a teacher to observe what pupils know or do not know, which gives a good opportunity to assess pupils' learning and their co-operative skills.

After pupils have filled the argumentation sheet, the teacher can engage them in a class-wide discussion. During the discussion, the groups should indicate the circuit diagram of their choice. Pupils may use the argumentation sheet to explain their reasoning by summarising their observations, and how these observations support their answer.

If groups have selected different circuit diagrams, teacher may raise a debate between these groups. During the debate pupils may use their counter-arguments and their rebuttals to challenge and to defend their own arguments. This is a good opportunity for a teacher to notice if some pupils have misunderstood the key ideas underlying DC circuits.

In the course of this paper, we have described the theoretical base and ways to utilise hidden circuits in teaching DC circuits at lower secondary level. Regarding the functionality of hidden circuits in teaching, they have been successfully used at lower secondary level. Our co-operating teachers have given positive feedback about the interest they awaken in pupils. With the help of videos, pupils can go through the hidden circuit tasks by using a computer, laptop, tablet, or smartphone. Using these devices in schools often increases pupils' motivation to carry out the tasks in hand [18].

The message towards hidden circuits from our co-operating schools is positive, and it has been stated that these circuits function also with heterogeneous groups due to their flexibility. However, pupils' learning whilst taught with the aid of hidden circuits has not been systematically tested. That being said, we think that hidden circuits could be utilised making teaching more motivating for pupils as a supplementary element for more conventional teaching but they might not function well as an individual element, unless enough guidance can be provided.

Supporting argumentation in physics teaching is important due to the fact that argumentation as an instructional practice is shown to be challenging for teachers. It may take years of training before the results obtained with argumentation-based instruction outperform the ones obtained with conventional teaching [19]. However, we think that engaging teachers to familiarise themselves with the use of argumentation in classrooms is useful, since it addresses valuable everyday skills, such as critical thinking.

We encourage teachers to develop this idea further. The material presented in this paper is addressed for grades 7–9 but we have successfully utilised simplified versions of hidden circuits also with younger pupils. It could also be extended for higher school levels, up to university level where circuits could also include other components than light bulbs. Hidden circuits could also be implemented experimentally; pupils should construct DC circuits with the same functionality as hidden circuits shown for them.

As to ease applying hidden circuits in teaching, we provide three example videos of hidden circuits and correct responses to them.

This project is a part of a 6 year national LUMA Suomi (STEM Finland)—development project coordinated by LUMA Centre of Finland. The aim of the project is to enhance learning of STEM subjects and making them more interesting for pupils during compulsory education. The project is funded by Ministry of Education and Culture of Finland.