Visualization Model For Electric Circuits
Gerald Tembrevilla, Yoshihiko Inada
(pp. 484-495)
The Asian Conference on Education
Official Conference Proceedings 2011
ISSN: 2186-5892
Proceedings URL: http://iafor.org/ace_proceedings.html
The International Academic Forum www.iafor.org

The Third Asian Conference on Education 2011 Official Proceedings
VISUALIZATION MODEL FOR ELECTRIC CIRCUIT
Gerald Tembrevilla
Okayama University, Graduate School of Education orion4010@yahoo.com
Yoshihiko Inada, Ph. D
Professor, Okayama University, Graduate School of Education y-inada@cc.okayama-u.ac.jp
Category: Math, Science, and Technology Learning
Osaka, Japan
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VISUALIZATION MODEL FOR ELECTRIC CIRCUIT
Gerald Tembrevilla 1 , Yoshihiko Inada 2
1 Okayama University, Graduate School of Education
2 Professor, Okayama University, Graduate School of Education
Abstract :
In a newly revised science-curriculum in Japan, the concept of energy is highlighted as an important concept across all levels and is first introduced to Grade 3 pupils as ‘stored force’ in a stretched rubber band or force of the wind. In Grade 4, electrical energy is described by comparing the brightness of bulbs or speeds of a battery and motor-attached toy car. In Junior high school, water flow model is used to define electrical energy ‘voltage’, electrical current and resistance. However, a number of researches claimed that water flow model creates confusion for students in differentiating energy and current. Other studies pointed out students’ difficulty in terms of the flow of charge and energy, and voltage and its relationship to current. From our analysis of selected electric circuit models, and taking into account the ‘energy concept’ presented in Grade 3, we developed a ‘Rubber Band – Net – Water Flow Model’ for electric circuit as a tangible visualization on how electrical energy is ‘consumed’ in the bulb. In a 30-min lecture-demonstration to the 29 Grade 4 pupils of the university’s attached elementary school, we analyzed the pretest and post-test results to elucidate the model’s role of establishing a connection and coherence in the way pupils define and visualize energy.
Introduction
Electricity is seen as a central area of physics and science curricula at all levels of education, namely primary, secondary and tertiary levels (Gunstone, Mulhall, et al., 2009). Hart (2008) outlined that this same topic itself poses many challenges for both teacher and students. In primary level, pupils may enjoy constructing simple circuits and finding out how to light the miniature bulb by connecting pieces of wire into the battery and miniature bulb. However, in the course of exploration puzzling observations might create dilemma even for teachers. Using equations and formulas to explain what has been observed in the circuit is inappropriate for beginning pupils, as they are already abstract representation of the circuit.
In junior high school level, some curriculum introduced different models like water flow model as analogy to explain the concepts of current, voltage and resistance. However, Gentner and
Gentner (1983) pointed out that ‘this model is not effective in showing the difference between the intertwined concept of current and energy when beginning students do not have the requisite understanding of water pressure and flow’. Potential difficulties of the said model are further accentuated by the tendency of textbook writers to describe the model using words as ‘push’ or
‘pressure’ to describe ‘voltage’, without making the model itself explicit (Mulhall, et al., 2001).
Furthermore, a study of Shipstone, et al., (1988) on 15-17 year–old students’ understanding of electricity in five European countries revealed that ‘students across participating countries substantially have common difficulties in understanding concepts which include flow of charge and energy, and voltage and its relationship to current’.
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Statement of the Problem
Since electricity occupies a prominent place even in primary education, how can primary school science teachers build a ‘starting bridge’ between the physical circuit for the grade school pupils and the abstract formulas introduced in junior high schools in order to facilitate coherence and continuity in the way students define and visualize electrical energy and other electrical terms?
Specifically:
1) What appropriate visualization can facilitate understanding on the concept of
‘consumption of energy’ in the bulb for Grade 4 pupils? (This topic is appropriate since
Grade 4 pupils are introduced to the circuit activity at this stage)
2) Can this visualization provide connection on the concept of voltage along the level of
understanding of Grade 4 pupils? (In Japan’s science curriculum the concept of voltage is
not introduced until pupils reach junior high school.)
Visualization in Science Education and Examples of Electric Circuit Models
Visualization is crucial in the production of knowledge. It can function as a ‘bridge’ between scientific theory and the world-as-experienced (Rapp and Kendeou, 2003). Since much of science involves the explanation of complex, casual relationships in dynamic systems, a visualization that captures salient relationships will enable students to understand the complexity underlying a conceptual theory. Gilbert (2007) outlined that ‘the roles of models and of visualization in science and science education have gained theoretical and practical saliency and that one emphasis is on introducing to students, on all levels of the education system, the nature and processes of science’. Other research (Seok and Jin, 2010) claimed scientific models are tested both empirically and conceptually and change along with the process of developing scientific knowledge.
Electricity is seen as a central area of physics and science curricula. Its concepts are highly complex in ways that understanding them is dependent on analogies and metaphors (Gunstone, et al., 2008). Taber et al. (2006) pointed out further that ‘electric circuits are abstract and students are expected to develop conceptual models of the relationship between non-observables qualities
(current, potential difference, resistance) in terms of other non-observables such as energy and electrons’.
Duit (1991) and Heywood (2002) have pointed out that models play an important role in teaching and learning physics. Textbook treatments of electric circuits for beginning students (Nardelli,
2006 ; Lofts and Evergreen, 2007 ) commonly assume an electron-transport model , explaining electric current in terms of the flow of electrons around a circuit. This model is described to fit comfortably within the realist ontological framework of physics (Hart, 2008). However, the model is often not made explicit and, in any case, cannot provide a complete and coherent account of how electrons are involved in the transport and distribution of energy around the circuit (Mulhall, et al. 2001 ; Stocklmayer and Treagust, 1994 ). As a consequence, as Gunstone et al. (2007) have shown, introductory texts may simply introduce the terms energy and/or voltage with little or no explanation and, in some cases, without even clear definition. Some introductory texts invoke Ohm’s law (Lofts and Evergreen, 2007 ) in an apparent attempt to explain energy transfers, but this is an empirical relationship that, by its very nature, cannot fulfill an explanatory
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The Third Asian Conference on Education 2011 Official Proceedings Osaka, Japan role in order to address the fundamental limitations of the electron transport model.
Some researchers (Mulhall, et al. 2001; Stocklmayer and Treagust, 1996) have argued that only an electric field model can illustrate the holistic reasoning about electric circuits, but its formal mathematical definitions are unhelpful for beginning students. Moreover, Stocklmayer (2010) pointed out that ‘field model is more coherent and overtly deals with the many misconceptions about direct circuitry identified in the literature’. Other alternative models are effective only on a single and specific concept. For example in Japan, Pachinko model is used to describe resistance.
In this model, marbles are represented by electrons that are sliding and colliding on an array of concrete nails that were planted on an inclined plane. Gentner and Gentner’s (1983) ‘ movingcrowds model’ is claimed to be effective in modeling resistance but weak in describing the concept of voltage. Hart (2008) introduced an effective way of differentiating energy from current through the use of Smarties as ‘energy’ and movement of students as ‘current’ but, posed some difficulties in explaining the distribution of energy across parallel and series circuits.
The use of overtly analogical models in textbooks, especially recent texts, appears to be quite rare, although Nuffield Primary Science (Nuffield-Chelsea Curriculum Trust, 1993 ) makes use of a bicycle chain mode l, where the chain represents the circuit, and each link an electron. Hart
(2008) described the system as ‘when the rider pedals, energy is supplied to the system at the pedal, and the movement of the chain transfers the energy to the wheels. The links in the chain are not used up and they are there whether or not the bicycle is operating, whether or not they are transferring energy. Energy transport is effective from the moment pedaling starts, and is not dependent on a particular link in the chain travelling from the pedal end to the wheel’. This looks simpler but she further stated that ‘bicycle chain model is already abstract in that the mechanism of energy transport is not immediately apparent. This makes it more difficult to distinguish
energy (transported through tension in the bicycle chain) from charge (represented by the links of the chain itself)’.
Rubber Band – Net – Water Flow Model of Electric Circuit
Development
The development of the Rubber Band – Net – Water Flow Model directly aimed to introduce the concept of electrical energy, a fundamental concept in basic electricity, as a ‘consumable substance’, and tangible experience for Grade 4 school pupils. The battery as a common representation of a source of electrical energy used in elementary level is like a ‘black box’. How it causes a current to flow is far more complex and difficult to visualize. Furthermore, explaining to the pupils the differences in the brightness of the bulbs or rotation of the propeller brought about by the differences of series and parallel connections of batteries proved to be very difficult.
In contrast, the concept of current, although invisible, is easy to describe with the use of galvanometers. By connecting a galvanometer between a battery and a miniature bulb in the circuit (Mori, M. et al., 2011) , pupils can verify the flow of electricity, though invisible. The strength of flow and direction of electricity is described according to the degree of deflection of the hand of a galvanometer and in what direction the pointer deflected. However, confusion arises when pupils were confronted with the fact that the readings from the two galvanometers attached oppositely on both sides of the circuit showed no changed in the currents’ readings. It is thought that our proposed model can provide a tangible visualization in addressing these concepts of ‘consumption of energy’ and ‘conservation of current’.
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The introduction of this model also aimed to explore possibilities on how the concept of electrical energy using the model can connect to the analogy of water pressure and voltage. Although the concept of voltage is not introduced until Junior high school, we reckon that the tactility of the model can provide avenues for pupils to establish the link between these analogies.
The Salient Features
The first highlight of this model is the utilization of the tangible and consumable idea of energy as a ‘stored force’ (Mori, M. et al., 2011) in a stretched or twisted rubber band. Using the water pressure-voltage analogy, Grade 4 pupils are able to confirm the change in pressure by squeezing and comparing the hardness and softness of the plastic vinyl tube. The change in pressure is created as the pupils pull and push a movable piston (which is connected to strips of rubber band tightly held by a metal clip attached on the outer acrylic pipe) causing the rubber band to stretch and to return to its original length (Fig. 3).
The second highlight of this model is the establishment of a concrete visualization of voltage owing to hydraulic pressure that avoids gravitational effect (Kameyama, 1980). Current water flow model utilizes water potential energy-voltage analogy. This analogy is closely linked to electric potential energy in electromagnetism, a subject that is difficult for the students to visualize. By utilizing a hydraulic pressure – voltage analogy (Electrical Circuit Analogy), our proposed model utilizes the build-up of water pressure as water flows in a decreasing crosssectional area of a pipe (Poiseuille’s Law). Augmenting this provision with a common fish or harvest net as depiction of a filament and small balloon to support the image of a miniature bulb, our proposed model can provide a tangible encounter for pupils to relate to hydraulic pressure.
In a nutshell, the stretching and returning action of the rubber band makes the water flow. This water flow in return, inflates the balloon, hardens and softens the plastic vinyl pipe and lets the water itself to go and flow back (water’s quantity kept unchanged) to the place where it was originally pushed. This action of ‘stretching and returning’ of a rubber band exemplifies the
‘charging and recharging’ of the battery for the ‘electricity to flow’ and this ‘flow’ inflates the balloon as equated to the glowing of a miniature light bulb, all done in a tangible, tactile and explicit manner. The materials used in this model are shown on Figure 1.
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#30 O band pack rubber band
Down corning grease
Small balloon
Acrylic pipe (outer)
OD-70mm,T-3mm
#16 Color wire
1.66mm
22cmx32cm
Harvest net
Grooved acrylic pipe(inner)
OD-60mm,T-8mm
Ordinary vinyl plastic
Net fitted into the plastic pipe
P48A O-ring
PI-75 Free
Metal band
Balloon attached plastic pipe
Check valve
Silicon stopper fitted in inner pipe
Inner acrylic pipe fitted with O-ring and flat tape
Transparent scotch tape
San-ei seal tape
PVC
Flat tape
Nichiban
Vinyl tape
#15 Silicon stopper
13mm elbow,
T connector
and cap
Connector acrylic pipe
14mm 9mm
Rubber stopper for the outer pipe
The Construction
Figure 1. The Materials
1. Grooved inner pipe mounted with O-ring, flat tape, silicon stoppers on both ends, with the check valve inserted inside it is fitted into the outer pipe.
2. Once fitted with the outer pipe, a handle connected to the rubber band is tied strongly on one end of the outer pipe using the metal clip.
3. Rubber stoppers with connecting smaller acrylic pipe, elbows, inlet and outlet pipe are fitted on both ends of the outer pipe.
4. Improvised pipe made from vinyl plastic with a balloon fitted on the plastic pipe with the net is
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The Third Asian Conference on Education 2011 Official Proceedings Osaka, Japan attached to both elbows from both ends of the outer pipe. (Once everything is fitted, water is filled through the inlet and outlet pipes)
2.
1.
3.
4.
Figure 2. Parts and components of the construction
The Operation
1.
Pull the handle for the piston (Fig. 3) to move opposite side as the rubber band stretches. This movement will allow the water to flow through the check valve opposite to the direction of the piston. The water will occupy the area vacated by the piston. This act is similar to an act of charging the battery. (The piston, outer pipe, handle, rubber band comprise the image of a
‘battery’)
2. Releasing the handle will cause the rubber band (Fig. 3-2) to return to its original size. This will cause the piston to go back to its initial place while pushing the water on its way back. This
‘push’ is an explicit and tangible way of demonstrating the ‘push‘ of a battery that will allow the water to flow through the pipe and back in the outer pipe. Although the pulling (Fig. 3-1) and releasing of the piston inflates and deflates the balloon, the main focus is the role of the net (as analogy for the filament) in building up the pressure difference that causes the hardening and softening (Fig. 3-2) of the tube. By utilizing Poiseuille’s Law to the pressure drop and voltage drop analogy, and at the same time providing a concrete representation of a filament in an actual circuit, we introduced the net as differentiated in its purpose from the research of (Fukuyama, Y. and Higashiguchi, S., 2004).
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The Third Asian Conference on Education 2011 Official Proceedings Osaka, Japan
1.
+
=
-
Pressure increases remains
2.
+
Note * Pressure
-
Figure 3. The tangible analogy for the battery and filament of the bulb
The Lecture-Demonstration
There were 29 Grade 4 pupils from Okayama University attached elementary school who voluntarily attended a 30 min lecture-demonstration using the Rubber Band – Net – Water Flow
Model. The pupils have already covered the topics on the ‘Workings of Electricity’ where they learned how to use the galvanometer to describe the magnitude and direction of the current, and differences of series and parallel battery connections in relation to the brightness of the bulb or speeds of rotation of a propeller. The pupils were shown a simple electric circuit as a review.
They were given two minutes to answer the 2-item pre-test after they correctly predicted that the miniature light bulb glowed as soon as the switch is turned on. The pre-test questions reflected the two objectives described in the beginning of this paper. Question number 1 asked ‘What kind of work does a battery do?’ Question number 2 stated as ‘What changes are taking place as current flows on each wire connected opposite the bulb?’ Before the model was presented, the pupils were shown a simple circuit where two galvanometers were connected separately opposite the bulb. They were asked to predict to the question, ‘Is the current on both wires opposite the bulb the same or will the readings on both galvanometers the same?’ Out of 29 pupils, 25 said
‘No’ and only 4 answered ‘Yes’.
The pupils were then led to the demonstration of the model (Fig. 4). Explanations were given on the identification and description of the parts of the model as paralleled to an actual simple circuit. They were asked to observe, to touch, to hold and to compare the hardness and softness of the vinyl plastic pipe as water flows through the net while inflating the balloon. Post-test was administered after the short demonstration. Discussions on what pupils had observed and learned followed after the post-test.
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Results and Discussions
Table 1 shows the summary of answers given by the 29 Grade 4 pupils for the Pre-test and due to voluntary basis, only 16 pupils remained for the Post-test, respectively. Pre-test and post –test answers for Q1 are identical and the same. This indicates that pupils have a common understanding and agreement on the kind of work battery does, even when they were made to observe and manipulate the concrete Rubber Band – Net – Water Flow Model. Pre-test responses for Q2 also indicate that pupils have common conceptions that current’s direction and strength change as it flows through the circuit passing the miniature bulb. However, answers in the Posttest for the same Q2 clearly indicate that majority of the pupils opted for different answers viewed as a result of intervention by the model, and probably some linked to persuasion by their classmates’ answers. Specifically, six pupils stated that water pressure in the tube had changed by citing the hardness of the vinyl tube on one side and softness on the other side of the net, respectively. Moreover, five pupils described a change in the voltage by relating it to the hardness and softness of the vinyl plastic tube. Although they could not accurately point out the cause in the change of either pressure or voltage, it could have been pursued if we have had enough time by making follow-up questions. Nevertheless, these pupils have introduced words, which appear to be advanced for their levels like ‘pressure’ and ‘voltage’. One pupil even used the word ‘taken’ representing the ‘push’ provided by the battery as equated to being ‘consumed’ in the bulb.
Moreover, two pupils still maintain that current’s strength had changed supporting the idea of
‘current consumption’, which still remains as an attractive and persistent notion of pupils
(Shipstone, et al., 1988) while two more pupils describe that current’s direction had changed. It was thought that had these 4 pupils were given enough time to observe and interact with the model they might have changed their answers, otherwise.
Table1. Pre-test and Post-test Summary
Questions/Answers Pre-test Post-test
Q1
Q2
Push the electricity to flow
Light the bulb
Direction of the current
Strength of the current
Push the electricity to flow
Light the bulb
6 pupils
Pressure had changed
5 pupils
Voltage had changed
1 pupil
Battery’s ‘push’ was ‘taken’ by the bulb
2 pupils
Current’s strength had changed
2 pupils
Current’s direction had changed
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Conclusion
Regardless of the decrease of the number of pupils in the post-test part, their responses in Q1 for both pre-test and post-test, and Q2 pre-test showed no difference and contradiction. The pupils have a common understanding on the ‘supposed’ function of a battery viewed as true in relation to their level, and majority of them hold the common pre-conceived idea of ‘current consumption’. The remarkable change was shown on their answers in Q2 post-test after the
Rubber Band – Net – Water Flow Model was presented. It was viewed that despite some degree of probability that some pupils’ answers in Q2 for the post-test were affected by persuasion of their friends and advanced learning, they were confident to introduce the words like change in
‘pressure’, ‘voltage’ and ‘energy consumption’ based from what they have observed from the model. Although only one pupil out of the remaining 16 pupils described the ‘energy consumption’ by pointing out the water as it passes through the net, it is very noteworthy to emphasize that 70% or 11 out of 16 pupils cited the hardness and softness of the vinyl tube as water passes through the net as a common reason to account for their different answers as
‘changed in pressure’ and ‘changed in voltage’, respectively. This result shows that the model can serve as a promising indication that pupils can be convinced that energy is the quantity that is
‘consumed’ in the bulb instead of electrical current or charge. Relating it to the definition of the pupils of energy as ‘stored force’ in a stretched rubber band, then this force allows the water to flow through the vinyl tube. This flow hardens the tube (connected before the net) as water negotiates to enter the net and softens the tube (connected after the net) as the water leaves the net. The hardening and softening of the tube shows the decrease in the ‘force’ of the rubber band as equated to the ‘consumption of energy’.
Further discussions of pupils’ ideas over the observed information using the model can encourage pupils to share sensory information to construct common representations that will link to the concept of voltage. Moreover, this shows that with further follow-up discussions and demonstrations using the model the hardness and softness of the vinyl tube could serve as a direct and concrete proof to support the ‘water pressure – voltage analogy’. This model is viewed as an appropriate design to offer the pupils with sensory information that supported a conceptual change on their notion of energy and current. These representations serve as a ‘window’ into pupils’ ideas and might provide teachers with communication and evaluation tool (Botzer and
Reiner, 2007). Basing from the answers of this same group of pupils, it is also noteworthy to mention that they did not indicate any change in the current’s strength on both sides of the circuit.
This indirectly shows that the idea of ‘current consumption’ can effectively and possibly be replaced by the notion of ‘energy consumption’ with the intervention of the proposed model.
Recommendations
Basing from the discussions and conclusions presented, the following items are introduced subject for further studies and confirmation:
1.
Refining the 30-min lecture-demonstration into a full-length lesson in order to facilitate ample and reasonable time for the pupils to manipulate and observe the model and at the same time provide more venues for them to explain and elucidate their thoughts.
2.
Making the model lighter so that pupils can freely manipulate it, looking for alternative replacement for vinyl plastic pipe and minimizing frictional effects between the piston’s
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O-ring and outer acrylic pipe for the rubber band to freely pull back the piston as it returns to it original length.
3.
Designing the model with provisions to quantitatively measure the targeted variables can be best fitted and introduced into the level of Junior high school students.
Acknowledgement:
The authors would like to express their gratitude to the Grade school science teachers (Mr.
Ikeda, Mr. Tsujimoto and Mr. Tanaka) and Grade 4 pupils of Okayama University attached
Elementary Grade School for their invaluable support and cooperation. We also acknowledge the sponsorship of SATO YO International Scholarship Foundation. This work was also supported by Grant-in-Aid for Scientific Research (C) 23501069.
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