Subject Studies Assignment
Teaching electricity to Year 10
Subject: Physics
Word count 7,906.
1
Introduction ........................................................................................................................... 3
Literature Review .................................................................................................................. 3
Research........................................................................................................................... 3
About learning ................................................................................................................... 4
Assessment for learning.................................................................................................... 6
Common misconceptions of electricity .............................................................................. 6
Use of analogies ............................................................................................................... 8
Teaching sequences ......................................................................................................... 8
Lesson sequence ................................................................................................................. 9
Planning................................................................................................................................ 9
Lesson Outlines .................................................................................................................. 11
Lesson 1: Charge and current......................................................................................... 11
Lesson 2: Current ........................................................................................................... 11
Lesson 3: Potential difference ......................................................................................... 11
Lesson 4: Resistance ...................................................................................................... 12
Evaluation ........................................................................................................................... 12
Lesson 1 evaluation ........................................................................................................ 12
Lesson 2 evaluation ........................................................................................................ 18
Lesson 3 evaluation ........................................................................................................ 21
Lesson 4 evaluation ........................................................................................................ 22
Conclusion .......................................................................................................................... 26
References ......................................................................................................................... 28
Appendices
A Lesson Plans and PowerPoint resources (1-4)…………………………………………..… 31
B Current and charge calculations worksheet………………………………………………… 55
C Homework on current and charge…………………………………………………………… 57
D Instructions for building voltage circuits…………………………………………………….. 59
E Circuit diagram tests………………………………………………………………………….. 61
F Results of circuit diagram tests………………………………………………………………. 64
2
Introduction
This report relates to a sequence of four one-hour lessons taught on the topic of electricity.
The school where these were taught was a selective, independent, all-girls school in
covering the age range of 3 to 18. There are around
around
girls in the school with
of those in the 11-18 age range.
I chose the topic of electricity for this study as this presents a number of difficulties for
teaching, partly because electricity cannot be seen or directly experienced. Additionally my
Year 10 class were scheduled to be taught electricity in January, which would be
convenient in terms of timing. In December I would be teaching electricity to a Year 9 class,
so I would also have gained an idea of what the Year 10 class would have been previously
taught. Finally this is a topic on which there has been much research into children’s ideas
about electricity and the misconceptions they may hold.
My class comprised of 18, Year 10 girls in a mid set ability class. Two girls had been
identified as having mild dyslexia. One had recently been given a laptop to use by the
Individual Needs department, but had opted not to use it in my lessons.
This class has two physics lessons per week and the sequence of four lessons was taught
over a period of three weeks on four consecutive lessons in January.
Literature Review
Research
I primarily used Google Scholar and the King’s College library to source research material.
By following the bibliography in articles and key books I was able to identify who the key
researchers have been, particularly in the area of models of electricity and misconceptions
that may be held by students.
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About learning
One of the early theories of learning argued that it is not useful to consider what goes on
inside the mind because this is not something that we can directly observe. On the other
hand we can observe behaviour, and we can measure how behaviours change in response
to stimuli.
Known as ‘behaviourism’, this theory of learning postulated two basic types of learning
known as classical conditioning (Pavlov, 1927) and operant conditioning (Skinner, 1974).
Skinner (1974) showed how specific behaviours could be modified in animals by rewarding
or punishing them. Whilst this theory has been applied to humans to modify behaviour, it is
less applicable to teaching students content and concepts.
A second branch of theories about learning are known as cognitive theories and these are
interested in the processes that occur in our minds. From the 1950’s Jean Piaget (1952)
developed his theory of child development based on his observations of children up to
around the age of twelve. He proposed that children went through a series of
developmental stages, with progression to the next stage dependent on the previous stage
being attained.
Piaget’s work has not been without criticism, for example because of the subjective nature
of his studies and his methodologies (Bryant, 1984). There are also arguments about
whether in fact learning occurs more continuously rather than in the developmental stages
he proposes (Adey et al, 2002). One idea that came from his work has persisted, and that is
the way that a new level or stage may be attained.
Known as cognitive conflict, this suggests that a child encountering a new situation that
they cannot accommodate within their existing ideas about how the world works, will cause
some reorganization in their minds to a new framework or schema. The overall process by
which each conflict and accommodation builds upon each other is known as constructivism.
Constructivism also recognises the importance that motivation plays in learning and argues
that the child must be actively engaged for the learning to occur.
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The implication for learning in the classroom is that a bored or dis-engaged class is less
likely to change their already held views about a particular subject. Instead children should
be encouraged to actively explore the subject, with the teacher acting as a facilitator
devising problems to create the disequilibrium or cognitive conflict that is required if a jump
to a new schema is to be achieved.
A further development of this theory came from Vygotsky (1978) who emphasised the role
of social context in learning. Whereas constructivism focuses on the individual, social
constructivists place more importance on the role of the people around you when learning.
He further argued that central to this process was language. He proposed that language
was not a result of thought, but that language and thought were inextricably entwined. It is
the act of talking about the subject that actually creates the constructs in someone’s
mind. In the classroom this means that as teachers we should encourage children to
discuss and explain out loud their thoughts and reasoning.
A further contribution from Vygotsky was the idea of the Zone of Proximal Development
(ZPD). This suggests that the child can learn most easily when being taught the stage just
above the stage that they are working at, rather than attempting to move children forward to
understanding a major new concept in one leap. In addition, it might not be the teacher who
helps a student understand the next step – it could be fellow students who have been
working just ahead of the one being taught. So in teaching a topic, group work becomes
another method through which students may learn, both from more able students
cementing their concepts as they try to describe what is happening and through other
students listening and learning from them.
Bruner together with others (Wood et al, 1976) further suggested what is known as
‘scaffolding’. This is the idea that pupils should work out the concepts themselves with the
role of the teacher being to provide some structured support.
I shall be taking a social constructivist approach to my sequence of lessons, by
encouraging hands on activities, using group work so that the students can verbalise their
thoughts and aiming to introduce ideas at just the right level.
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Assessment for learning
Whilst assessment is sometimes used for accountability or reporting purposes, assessment
for learning, also known as formative assessment, is concerned with providing a feedback
mechanism so that teaching can be adjusted to optimise learning.
There are essentially two processes in formative assessment. The first is to elicit what the
pupils know, partly know or do not yet know. It is important for both the teacher and the
students to recognise this. The second process is for this information to be used to adjust
the teaching that then follows.
Evidence for the effectiveness of this approach was summarised in a review of research
published in 1998 (Black and Wiliam, 1998) which showed that it could raise standards of
pupil achievement. They calculated an effect size by measuring the increase in pupils’ test
scores with the range of scores typically found and showed that effect sizes of between 0.4
and 0.7 could be achieved. These are larger effect sizes than can be found with many
interventions, showing that this can be a very effective technique to employ when teaching.
Common misconceptions of electricity
A major issue with understanding how electricity works is that it cannot be directly observed,
unlike some other phenomena encountered in physics. There has been much research on
what alternative theories or misconceptions children may hold about electricity and how
successful approaches may be to changing these.
Research such as Shipstone (1985) has investigated the common models that children hold
about electricity. These include:
A. The single wire model, where only one wire to a bulb is required to make it light up
B. The ‘clashing currents’ model where current flows both ways in a circuit. Where they
meet, such as at a bulb they clash and react, much like how a spark can be
observed at a meeting point
C. The dilution of current, where current gradually decreases as it is consumed around
a circuit
D. The correct scientific model of the same current all the way around a circuit.
In the age group that I shall be teaching (14-15 year olds), Osborne and Freyberg (1985)
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have shown that 10% of my students may still be using the model B, whilst others
(Shipstone, 1985) have shown that around 50% will be using model C.
A further issue that I may encounter comes from neuroscience studies, namely that
introducing a new concept does not necessarily displace alternative concepts that a child
may hold. Goswami and Bryant (2007) noted in their review of research into children’s
cognitive development and learning “Cognitive neuroscience studies suggest that when we
learn particular scientific concepts, such as the Newtonian theory of motion, these concepts
do not replace our misleading naïve theories. Rather than undergoing conceptual change,
the brain appears to maintain both theories”.
This has been shown directly with children’s models of electricity. For example children
expect that they can change from one model to another quite freely (Solomon, 1983). This
means that if I have successfully taught a model for circuit diagrams they may not transfer
this understanding to a differently presented circuit and instead use one of their previous
models. The implication is that I will need to reinforce the model at multiple stages and
lessons.
A concern for the ‘stickability’ of any new models comes from the research of Cosgrove et
al. (1985) who showed that even when students had been shown to be using a model of
electricity that they have just been taught, when tested a year later they had reverted back
to their previously held models. This is not something that I can directly deal with in my
sequence, but it emphasises the difficulties of moving children to new models.
Interestingly Gott (1984) showed that even though 15 year olds showed a set of
disappointing results for their understanding of electricity they could demonstrate
considerable skill in connecting electrical circuits. Cosgrove (1984) further showed that very
young children could solve circuit puzzles even when they had not been taught any
concepts of electricity. This suggests that experience in working with circuits may not
directly transfer to knowledge of the key concepts, unless I explicitly make them.
In considering these findings, Shipstone (1988) argued that as the concepts in electricity
are complex and that most students should never need to use the scientific model for
electricity in their everyday lives, there is no point in teaching them the models. Instead you
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should focus on how to use electricity and to do so safely. Apart from the reality that I have
to teach students for their exams, I also feel an obligation to try and aim higher for my
students than Shipstone’s modest though utilitarian proposal.
The research shows then that I should expect students to come with their own models from
previous teaching, that they may not immediately use any new model I present and they
may switch between models during their learning.
Use of analogies
So what approach should I take to developing the scientific model in children? One
approach to teaching electricity is to use holistic analogies to cover the complete system of
electricity. One such example is the water analogy. Schools have sometimes created a
physical layout of tubes with reservoirs, pumps, pipe constrictions and valves, designed to
be equivalent to resistance, current etc. in electricity. A problem with this analogy is that it
implies that children already fully understand these concepts about fluids and this may well
not be the case (Schwedes, 1984). A similar argument can be made against using a
thermodynamic model.
Rather than adopting these complete system analogies I intend to use analogies in smaller
steps to model a specific idea about electricity and so work within the ZPD of the child. An
example would be modelling how current flows and how energy can be transferred from the
battery to a bulb by using a bicycle chain analogy or a line of marbles.
Teaching sequences
A common sequence is to move from current to voltage to resistance. One problem with
this approach is that current is seen as the dominant idea and can lead to students develop
a sequential view of electricity essentially stemming from their existing ideas of cause and
effect. Voltage can become viewed as a property of current.
An approach to counter introducing this misconception is to explore voltage first, at least at
the level of the battery (for example Psillos at al, 1988). The intention is to help to dispel the
idea that a battery maintains a constant current (see Cohen et al, 1983).
Sometimes energy is taught at the start of a sequence (Licht, 1991). However I am not
8
convinced that introducing energy at this point helps, because students already are
grappling with the three concepts of voltage, current and resistance.
Although my students will have been taught models for current and voltage in prior years,
the above research shows that I cannot assume that they will retain or use these models. I
plan to use formative assessment to understand what models are being used and adjust my
teaching to this. Given that students may switch between models I will need to keep
checking which they are using.
Through feedback I also intend to judge where their ZPD is and so adjust the teaching to
take this into account.
Lesson sequence
The school’s physics Statement of Work showed that the class had been taught electrical
circuits and current in Year 7 (about 6 lessons), and in the Autumn term of Year 9, they had
covered static electricity, current, potential difference and resistance (around 8 lessons).
Consequently the content that I planned teach would be covering concepts previously
taught in Year 9. The sequence planned covers two lessons on current, before moving on
to potential difference and resistance. The only new idea for the students would be the link
between potential difference and energy.
Planning
The sequence for teaching takes charge as the starting point and explains current as a flow
of charge. Charge is explained via the model of an atom, with free electrons explained as
the charge carrier in metals, before moving on to models of current derived from the rope
model.
The second lesson explores current in more detail to see what affects it in a circuit so that
they have a qualitative understanding of current and its relationship with voltage and circuit
components. Some sources have advocated teaching potential difference before current
(Psillos et al, 1988), as otherwise students may come to see voltage as an attribute of
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current rather than a cause. To help avoid this pitfall, the question of what makes the
charge move is dealt with at the start of lesson 2 with a cell/battery/power source defined as
a fixed voltage device.
Potential difference is then taught in lesson 3 with the new concept of how it relates to
energy. Finally the last lesson defines resistance and recalls Ohm’s law.
To gain some understanding of the types of misconceptions that the students may have, a
short test was employed at the start of the lesson sequence to specifically explore current.
After the concepts around current were then explained in this first lesson, the same
questions were repeated. The research (e.g. Solomon, 1983) has shown that the models
that students use may well be resistant to change, or that they may hold several conflicting
models, so repeating this test would provide some indication of how resilient their models
may be to change. The results could then inform some of the planning for the future lessons.
The lessons cover the concepts of charge, current, voltage and resistance. They also cover
the equations of Q=IT and R = V/I and how to calculate current and voltage in series and
parallel circuits. The concepts should help to inform both the calculations and in circuits
and formula should help to reinforce the relationships between the concepts. The students
will also be taught to practice using the formulae and to predict measurements in circuits as
these also form part of the iGCSE specification.
In the final lesson a series of questions to again cover the three models of current along
with predictions about circuits would be used to evaluate what the students had learnt.
In line with constructivist ideas about learning, the lessons were planned to maintain
interest through variety and for students to be active in their learning. PowerPoint slides
were combined with the teacher writing on the whiteboard to model drawing diagrams or
completing equations. Interactive tools were used where they had specific advantages over
slides. Physical models were used for demonstrations using volunteers to assist whenever
possible rather than just having the teacher “own” the equipment. Finally the students would
also have practice handling and building circuits themselves so that the ideas and results
could be experienced personally.
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Lesson Outlines
The lesson plans and PowerPoint resources may be found in appendix A.
Lesson 1: Charge and current
Lesson objectives:
•
Understand that current is the rate of flow of charge
•
Know and use the relationship Q=It
•
Know that electric current in metals is carried by electrons
•
Identify common insulators and conductors
•
Understand the convention for current flow
•
Understand that current could be a flow of ions in an electrolyte
Outline
•
Test on three key misconceptions
•
Conductors and insulators, charge and current, atomic model and metals,
demonstrations of models for current
•
Retest of the three misconceptions
Lesson 2: Current
Lesson objectives
•
Understand that the driver for current is an electric field and that a cell produces a
fixed voltage
•
Understand how changing components and voltage affects current
Outline
•
Recall previous lesson
•
What makes current flow, interactive circuits on main board, demoing current in a
series circuit,
•
Practical to explore the effect of voltage and components on current in a series
circuit
•
Current in series and parallel circuits using interactive tool
Lesson 3: Potential difference
Lesson objectives
•
Understand that potential difference is the energy per unit of charge
•
Know how voltage is calculated in series and parallel circuits
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Outline
•
Recall previous lesson
•
Energy in a circuit, demo with motor, voltage explored using interactive circuit
diagrams
•
Practical to predict and measure voltage
•
Test on current and voltage sin series and parallel circuits
Lesson 4: Resistance
Lesson objective
•
Know the relationship between resistance and voltage and current.
Outline
•
Reintroduce the bead model for a parallel circuit, recap resistance, plot IV graphs
using live data logger to understand resistance, explain the significance of the
straight line, Ohm’s law
•
Test to check on understanding of current and voltage and of some common
misconceptions
Evaluation
Lesson 1 evaluation
The research suggests that students at this stage may still hold some misconceptions
(Osborne and Freyberg, 1985). Consequently I first wanted to establish if they were using
them. This was done at the start of the first class by asking three simple questions.
Diagrams or circuits were drawn on the board and the students responded using mini
whiteboards. Three misconceptions were presented based on research (Shipstone, 1985)
The diagrams used for the questions on misconceptions
12
To avoid students copying each other, students were instructed not to speak to their
neighbours and only to hold up their boards when asked as a whole class.
The students were asked to write down in their books a list of insulators and conductors. A
quick check of their progress indicated that they were not easily recalling this from Year 9,
with few examples being written down, so instead individuals were asked to name some. As
they still struggled and this was perhaps outside their ZPD, they were asked where they
might find insulation materials. With this prompt, they started to be able to come up with a
number of good examples of both types.
With a little more prompting they were able to recall the units for charge and that current
was a measure of charge flow per second. The shuttling ball demo was then used to
indicate a charged object moving (the ball) and the ammeter in the circuit indicated a flow of
charge. A couple of students that were asked, were able to describe what was happening in
terms of charges and attraction and repulsion.
The relationship between charge and current was reinforced by the students completing
some calculations using Q=It (see appendix B). The first question was completed on the
board, reminding them of the standard approach that the school’s physics department was
teaching: write the equation, rearrange, substitute in values, remember the units.
Following this a focusing question was used: “Why does the current flow easily in a metal?”
This was explained by referring to a drawing of an atom. They could identify the electron
shells and the nucleus. It was explained that the electron in the outer shell was a free
electron that could actually move across to another atom. A diagram of a group of atoms
was shown with free electrons moving randomly amongst them and it was explained that
when an electric field was applied they started to drift in one direction.
A previous lesson with a Year 9 class had shown that even after a rope model of current
had been shown the students thought that the electrons must come from the battery and
travel around to the bulb to have any effect. They had also thought that the wire may be
filled with more electrons after being used to carry a current. It was for this reason that the
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explanation of the source of the electrons was introduced, so they are reminded that free
electrons already exist in the atoms of a metal.
Following this, a classic model for current was used based on the rope model. The use of a
rope tied into a circle has the advantage that you can involve a large number of students
physically holding a rope. You can also model a battery by having someone start to move
the rope through their hands. However in practice the forces mean that it doesn’t easily run
through everyone’s hands and the only way to keep it moving is for several students around
the rope to also help pull it along. Thus the ideas about friction/resistance and
pulling/batteries start to become blurred.
It does show that something is flowing and all at the same speed, but there is no direct
connection to particles. You can alleviate this to some extent by drawing dots on the rope
or tying things to it to represent an electron or unit of charge, but the student has to start
connecting several concepts together in their head. You also have the possible distraction
of a large knot in the rope. Our attention is always drawn to changes or differences so it
would be best to eliminate this if possible so the students are just focusing on a line of
“charges” moving together.
Because of these limitations a variation of the rope model was used: a bead chain (a
Christmas street decoration). This was tied into a loop and glued so that the join could not
be seen. The beads represent electrons or an amount of charge. Visually it becomes
easy to see “current” being the rate at which beads pass a point and they can also be felt.
Bead chain
14
A 2m length of beads was employed which meant that three students helped to keep it in a
rough circle. The link back to the atoms was explicitly made so that they could see that the
electrons already existed in the wire and the battery started to make them all move, in the
same direction and at the same speed around the wire.
Another key idea was explored by considering the time it takes electrons to move. A simple
series circuit with a buzzer was constructed and when the switch was closed, the buzzer
sounded. Then a long length of copper wire was produced (co-axial cable striped back at
the end to show the central copper wire) and the students were asked to run it around the
length of the outside of the room (about 30 metres).
They were asked to predict if the buzzer would take less time, the same or longer to sound.
They were allowed to discuss as a group and replied quite emphatically that it would take
longer. The switch was closed and they were surprised to find that it appeared to take no
longer at all.
It could be argued that the question encouraged the creation of a misconception that may
not have existed beforehand. However whether they had the misconception or not is moot
as the objective was to create a surprise and force a cognitive conflict. The bead model
they have just been shown beforehand can be used to explain why there is no delay,
because as soon as one bead moves, they all move.
It was explained that electrons do not travel from the battery to the buzzer at the speed of
light but in fact drift very slowly, a few millimetres a second for example. This produces a
mystery as to how the buzzer could sound if they are assuming that the electrons still have
to travel from the battery to have an effect on the buzzer.
A second model was introduced to reinforce the bead model consisting of a line of marbles
balanced on a strip of plastic curtain rail and all touching each other. A small domino of
wood is placed at one end.
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Marbles lined up on a piece of curtain rail
The marble at one end is pushed and the last marble at the other end topples the domino
over. It was explained that the electrons act like the marbles so that when one is pushed at
one end the effects can be very quickly felt at the other, without having to assume that the
electrons or marbles travel all the way to the domino. The link was made back to the beads
being the electrons in the wire already being in place. The effect of connecting the battery
is to start the electrons drifting slowly through the wire but this effect is felt immediately all
the way through the wire. The word “drift” rather than “move” is used repeatedly to
reinforce this idea.
Having established that current is a flow of charge, and the charge in metals are electrons,
the students were asked what other things had charge. They offered ions as an example
and this led to how a flow of ions would also, by our definition, be a current. Using an
electrolyte as an example they were asked which way current was flowing if some ions
were negative and some were positive. Then the historic reason for this was explained and
why we draw current as positive to negative even though electrons in metals travel in the
opposite direction. By introducing that idea after ions the inconsistency does not appear so
great for students.
At the end of this lesson the same three questions asked at the beginning were repeated,
again using mini whiteboards as a method for responses.
The table below compares the answers at the beginning with those at the end of the lesson.
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Question
Incorrect
Incorrect
before
after
1 (one wire)
1
0
2 (current used up)
5
3
3 (current flow)
5
6
Count of incorrect answers – 18 in class
Only one person thought that the bulb with only one wire would light up at the start of the
lesson. It is possible that the person could have misunderstood the question so it is hard to
draw many conclusions from this. For example many cables actually contain two wires and
the picture could be perceived as being symbolic.
The results showed that two students overall had changed their view that current is not
used up. They had not been explicitly taught that current is not used up in this lesson
although they would have been taught this the previous year. The bead and marble model
do suggest that current is not used up – the electrons keep travelling around and do not
disappear in a component like a buzzer, but this was not explicitly stated.
This implied that the model alone was not enough for everyone to know that current would
be the same all the way around a series circuit.
The results for the third question are harder to understand as the bead model and the
marbles and discussion of charges and electrons flowing were all explained with them
flowing in a continuous loop. Although most students were correctly answering the
questions both at the start and end of the lesson, there was in fact one more person by the
end thinking that the way to indicate current was using an arrow from the battery to a
component. However if we recall the research into how children use their models they
appear to be content to hold several even conflicting models and use them in different
situations. The research also shows how resilient those models may be to change, which
these results appear to confirm.
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Lesson 2 evaluation
The results from the previous lesson suggested that it would take more than just showing
students a model, and it would take repetition of the models and links being made explicitly
for them to be useful.
The second lesson began with three questions on the board which they respond to one at a
time using the mini-whiteboards. Rather than serving as an evaluation, the objective was to
remind then about some of the concepts that they have been taught the previous lesson
which was in the previous week. If there had been a substantial minority that had incorrect
answers this would have indicated that I needed to change my lesson plan to go over some
of the ground from the previous lesson. In fact there were only one or two incorrect so a
quick reminder of the answers was sufficient.
The lesson started with asking why the charge moved and explaining that it is from an
electric field, starting to link the idea to those of static and charge attraction and repulsion.
Also at this point voltage was mentioned briefly and a cell was described as a fixed voltage
device.
Some approaches to teaching electricity advocate teaching voltage before current. I had
chosen to teach current first, but wanted to attribute the movement at least to the cell
without going into too much detail at this stage.
The previous lesson had shown that a number of children still were showing current as
going towards a component from both ends of the battery. Even though we had gone
through the bead model, they were not transferring this knowledge to a circuit diagram.
Because of this the lesson explicitly made the connection to the model and used circuit
diagrams with arrows to emphasise the current direction
The online tool “Circuit Builder” from vendor eChalk was employed for this rather than using
drawings. This tool, which was projected onto the main board, allows you to construct
interactive circuit diagrams and optionally reveal the values for current/voltage and
resistance through or across components. You can also switch the tool to show a visual
18
representation of components or a circuit diagram using standard symbols. In this way I
hoped to build links between circuit diagrams and physical layouts.
Two screenshots from eChalk’s Circuit Builder application showing the two types of display
that the user can choose
Another useful feature that was employed was adding in a switch. The students were
asked to predict if readings on the ammeters would be different and then the switch can be
closed to show a reading. A further feature is that the blue arrows indicate the direction of
flow of current. This was pointed out to reinforce with the students that current flows in a
loop, something that the previous lesson had shown was needed.
Next a real series circuit using cables with three ammeters connected was demoed and a
student read out the readings on the ammeters, to show that the theory translated to
practice. The students then began an activity in pairs to explore how current would be
affected when components were added to a series circuit or when voltage was changed.
Constructivist theories of learning tells us that students need to be active in their learning,
and so physically building electrical circuits helps students to see the relationships between
current, voltage and different components. There are some practical difficulties with
building circuits. One is that students may struggle to link a circuit diagram to an actual
circuit. With cables crossing each other they can become confused as to what they have
actually built. A second problem is that poor connections create points of high or varying
resistance, so that circuits connected correctly appear not to be conducting any current.
19
Consequently the students’ circuits were checked and for those that were struggling they
were shown how to lay the cables out in a circle to help them check if they have correctly
connected the components in series. This work in pairs gives students a chance to
verbalise their thoughts and predictions to each other – important from the Vygotsky point
of view.
A check of their books indicated that they were poor at constructing data tables for their
results and this was noted for subsequent lessons. A number of their conclusions were
reviewed out loud to the whole class and they were all sensible conclusions.
To conclude the students were questioned on a number of different circuits to predict the
current readings using another online interactive tool from eChalk called “Electric current:
Learn and Assess Quiz”.
This shows ten different circuit diagrams of increasing complexity to which you have to
predict ammeter readings at different points around each circuit. Weaker students were first
targeted to judge if they had understood the series circuits. They all answered correctly
and they were also giving good explanations as to why they gave those answers such as
“the current keeps flowing”, “because the current isn’t used up”, and “the same goes in and
comes out”. The tool allows you to skip questions so rather than continuing with series
circuits we moved to a three way parallel circuit to find the point at which they would start to
get the answers wrong. In fact they were all getting the answers correct combined with
good explanations for them such as “the current splits”.
One student asked why the current did not split evenly. It was explained that the resistance
to the current was different and that if the resistance was the same the current would split
evenly between the two branches of the parallel circuit.
They were finally given homework (see appendix C). This was in two sections: the first to
have them practice some basic calculations using Q=It. The second section was intended
to reinforce the words we had been using in the lesson: free electrons, the charge of
electrons and ions and the direction of flow of current compared to electrons. There was
also some reinforcement of current in an electrolyte which had been dealt with briefly in the
first lesson.
20
Lesson 3 evaluation
The lesson started with a couple of questions that they answered using mini whiteboards.
The first checked their understanding of free electrons and the second recalled their
answers to the practical they had completed the in the previous lesson. As their answers
indicated a good understanding the lesson progressed.
This lesson was designed to go over potential difference. This was introduced by linking
the idea directly to energy by building a series circuit with a small motor. Ideally the motor
would have been attached to gears or a mechanism to wind up a string to raise a weight,
but unfortunately the technicians could not find any suitable way to create this. Instead a
small strip of paper was attached to the axle, to make the motor’s spin more visible and
also audible. By increasing the voltage, it was shown that the motor would spin faster and
created more noise.
Light bulbs alone could have been used, but it was suspected that students might associate
a motor running with energy more readily. Light may not feel like energy being transferred
and the bulbs commonly used in battery circuits do not usually produce much heat.
A definition of voltage was then given associating energy and charge.
Pre-built series and parallel circuits were demonstrated using the interactive eChalk Circuit
Builder application to consider how energy is transferred around a circuit. A model of a
ruler pushing over a domino was used to show energy could be transferred from one point
to another even though the original force was not close to the domino. An analogy was
drawn to the marble model used in lesson 1.
Again students in pairs were given an activity to build five separate circuits and measure
the voltage in them. In the final two circuits, which showed two lamps in series and then in
parallel, they had to predict the voltage in one part of the circuit before measuring it (see
appendix D).
Connecting voltmeters in parallel can be problematic as students can get their wires
confused. For a couple of pairs who were struggling, it was suggested that they build the
21
circuit first using red cables then attach a voltmeter in parallel using blue cables. This gave
them a two-step process and colour prompts so they could visually group the circuit and the
voltmeter separately.
This lesson was completed with a selection of five circuit diagrams with questions on
current and voltage (see appendix E). The aim was to see how well they were able to
correctly calculate current and voltage which would be used to judge how much time would
have to be spent on this in the next lesson. The results showed that a few students had
inconsistent results, for example they calculated voltage correct in two parallel circuits but
not in two others (see appendix F). This was interpreted as carelessness rather than a
fundamental misunderstanding. Three students however did show that they were applying
an incorrect rule consistently and this was in calculating voltage in parallel circuits. This
indicated that this should be covered again in the final lesson.
Lesson 4 evaluation
The final lesson began with some questions on what current and voltage were, to be
answered on mini whiteboards. A third question asked about voltage in branches of a
parallel circuit which a few got wrong. The rule was then explained using a diagram drawn
on the whiteboard. The wording of the question was possibly not ideal and this may have
contributed to some of the incorrect answers. It would probably have been better to have
started with a circuit diagram.
Following this homework was returned. An analysis of the homework showed that all but
two students had difficulties when mA instead of Amps were used. The words for milli and
kilo were recapped and a calculation using mA was worked through on the board by the
teacher. The homework set at the end of this lesson which concentrated on resistance
calculations included a number of calculations in mA, MV and other measures to give them
practice.
A variation of the bead model was reintroduced in lesson 4. This had been designed in
conversations with a fellow teacher at the school who had been interested in adopting the
bead model himself. The beads were now attached to a board and an improvement was
made to model the battery better by adding in a crank shaft to drive the motion of the beads.
Spinning cogs held the beads taut and although it meant that the beads no longer needed
22
to be held by students, they did make the beads move very easily. Further a parallel circuit
was modelled using two strings of beads, being powered by the same crank shaft. This
showed how current “splits” at the junction of the parallel branch.
Equipment built to model electricity in a parallel circuit, as used in lesson 4
It was recalled that current is the rate of flow of charge and by counting the number of
beads passing a point in a second you could have an indication of current. It is then easy to
see that there will be fewer beads in a second in a parallel branch compared to a section
near the crank handle. Voltage was modelled in that the “pull” of each bead is the same in
each branch.
A couple of removable rollers were added to the middle of each parallel branch to indicate
an increased resistance. This showed that to keep the current moving at the same rate, a
bit more force had to be applied to the crank shaft – a greater voltage required to keep the
current the same. Students were questioned on what was a model of what and they
showed that they had understood what parts of the model indicated what aspects of
electricity.
The lesson progressed to recap the definition of resistance, followed by some practice of
calculations using the formula R=V/I. The questions were ordered so that the initial ones did
not require any rearrangement of the formula, but subsequent ones did. They were again
reminded of recently agreed standards in the physics department for how they were
23
expected to work out the answers using: formula, re-arrange formula, substitute values,
units.
To complete the section on resistance the students were asked to consider how it might be
useful to predict resistance. This progressed to a demonstration of a method to examine
resistance using a potential divider circuit that had been already set up to measure the
current through and voltage across a piece of thin wire. The details of the circuit were not
explained other than how it was used to change the voltage and measure the current.
Pasco data loggers were used so that the current and voltage could be immediately
projected in real time onto the board. Once the principle had been explained the display
was switched to an I V graph. With the data logging turned on, the software takes a
reading several times per second and plots a point for each reading on the graph. By
adjusting the rheostat, about a hundred readings can be obtained in a few seconds.
The graph clearly showed the creation of a straight line and a student correctly identified
this as showing that “current was directly proportional to voltage” for this wire. Suggestions
were then asked for what would happen to the resistance if we used a thinner wire. After
some discussion amongst students they agreed that resistance would increase and one
student predicted what the line should look like on our IV graph with some prompting by
thinking about what the current reading might be for a given resistance compared to the
existing line. A couple of volunteer students then manipulated the apparatus to plot a
second line on the same chart, which indeed followed their predictions. Ohm’s law was then
introduced.
Upon reflection it may have been better to initially show them some IV graphs that were not
straight lines as the idea may be in their heads that everything has a fixed resistance. After
all they have come across resistors which are marked as having a fixed resistance. So a
filament lamp, diode or semi-conductor may have been better, introducing them only as
materials whose resistance may vary. Then the discussion could have discussed how to
calculate the resistance at a number of different points.
24
The final part of this lesson comprised of a test, once again using the three questions asked
in lesson 1, followed by both qualitative and quantitative questions on current and voltage in
series and parallel circuits.
The table below shows the results for the first three questions. Although all but one person
indicated the direction of current flow correctly, there were still four students who predicted
that current would be reduced in a series circuit after a bulb, despite the teaching over the
four lessons.
Question
Incorrect before
Incorrect after
Incorrect after
lesson 1
lesson 1
lesson 4
1 (one wire)
1
0
0
2 (current used up)
5
3
4
3 (current flow)
5
6
1
Comparison of incorrect answers in Lesson 1 with Lesson 4 – 18 in class
The table below shows the count of incorrect answers for the other questions. Although the
numbers are small it suggests that the students may have more difficulty in recognising
what the question is asking, as clearly some had difficulty in correctly answering a question
qualitatively but when presented with a circuit diagram could apply their knowledge
correctly. In reflecting on the questions, perhaps improvements could have been made to
their wording which would have made them clearer and so shown greater consistency with
the results for the calculations. See appendix A for the wording used in the questions.
Word based
questions
Circuit diagram
questions
Current in series
5
1
Voltage in series
2
2
Current in parallel
4
4
Voltage in parallel
5
3
Count of incorrect answers to voltage and current in series and parallel circuits – 18 in class
25
Conclusion
Given that the study was conducted in a selective school and the class had previously been
taught about current, voltage and resistance, it was doubtful if any students would prove to
hold any misconceptions. However the initial testing showed that there were indeed a small
number that did hold some of the common misconceptions that Shipstone identified.
Although the retesting at the end of Lesson 1 and again at the end of Lesson 4 indicated
that there may have been some reduction in the misconceptions being used by students,
the teaching had not eradicated them. This does appear to reflect what Solomon (1983)
found in the resistance of shifting students’ models.
Did the tests really reveal how they were using the concepts? It could be that they
understood the bead model perfectly well, but were just not applying it when asked question
about a circuit. Although I made links and references in the lessons to the marble or bead
model, perhaps I need to be even more explicit and ask then to use the model to work out
an answer.
Another clue may be in the results of the test conducted in Lesson 4 which showed that
students were applying rules inconsistently. Some of this inconsistency could be because
they were making mistakes rather than showing an underlying misunderstanding and the
results from the circuit diagram questions in Lesson 3 suggest that this may be the case
given that rules were correctly applied to some circuits but not to all. However it could also
be because the students are learning rules to work out answers to circuit diagram questions,
but are not basing them on any understanding of why the rules exist.
The implication for teaching could be to avoid teaching any circuit diagram calculations until
models for current, voltage and resistance have first been taught. In this school this was not
the approach that would have been adopted in Year 9 when they were first introduced to
electricity in detail.
I conducted most of the tests using mini-whiteboards. This is a very useful technique for
assessment for learning as you very quickly get an overall idea of where the class is at and
you can adapt your teaching in that lesson and the next accordingly. However a weakness
of my use of these in these lessons was that I did not track the answers by individual and
26
instead only looked at a count for the whole class. The result was that it was harder to
differentiate more specifically and follow up with those who had misconceptions. Instead I
recognised when a concept was not fully understood by some and so taught that concept to
the whole class and expected that everyone would grasp the ideas. Adopting an approach
of focusing on the few who did not understand and following them more closely might help
eradicate the remaining misconceptions.
Finally although the techniques and models used appeared to be clear and useful, based
on the immediate feedback from the students, I may have been ‘preaching to the converted’
as most students appeared comfortable with explaining how electricity worked. The
approach to teaching electricity adopted here may have more value when teaching
electricity to earlier years, such as Year 9. Clearly by the end I still had not reached all of
the class and a more differentiated approach may have yielded an improvement in results.
27
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