Experiments for students with built-in theory: ‘PUMA: Spannungslabor’ – an augmented reality app for studying electricity

Abstract

With the help of augmented reality apps objects and text can be added virtually to the physical world (e.g. physical experiments) in real time. The augmented reality (AR) app ‘PUMA: Spannungslabor’ enhances simple electric circuits experiments for students with virtual representations based on the electron gas analogy including visualisations of interior processes in various components such as lamps and resistors. This opens up new possibilities for connecting theory and experiment in secondary school physics teaching. While using the AR app students are enabled to acquire qualitative and semi-quantitative knowledge about the basic concepts of current, voltage, potential, and resistance as well as the laws of series and parallel circuits easier and more directly. This holistic approach of learning through experiments can facilitate a deeper and more interconnected understanding of the topics covered in physics lessons.

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Phys. Educ. 57 (2022) 045024 (8pp) iopscience.org/ped
Experiments for students
with built-in theory:
‘PUMA: Spannungslabor’
– an augmented reality
app for studying
electricity
Christoph Stolzenberger∗, Florian Frank
and Thomas Trefzger
Department of Physics Education, Julius-Maximilians-University, Würzburg, Germany
E-mail: cstolzenberger@physik.uni-wuerzburg.de
Abstract
With the help of augmented reality apps objects and text can be added
virtually to the physical world (e.g. physical experiments) in real time. The
augmented reality (AR) app ‘PUMA: Spannungslabor’ enhances simple
electric circuits experiments for students with virtual representations based
on the electron gas analogy including visualisations of interior processes in
various components such as lamps and resistors. This opens up new
possibilities for connecting theory and experiment in secondary school
physics teaching. While using the AR app students are enabled to acquire
qualitative and semi-quantitative knowledge about the basic concepts of
current, voltage, potential, and resistance as well as the laws of series and
parallel circuits easier and more directly. This holistic approach of learning
through experiments can facilitate a deeper and more interconnected
understanding of the topics covered in physics lessons.
∗Author to whom any correspondence should be addressed.
Original content from this work may be used
under the terms of the Creative Commons
Attribution 4.0 licence. Any further distribution of this work
must maintain attribution to the author(s) and the title of the
work, journal citation and DOI.
1361-6552/22/045024+8$33.00 1 © 2022 The Author(s). Published by IOP Publishing Ltd

C Stolzenberger et al
Keywords: augmented reality, AR, electricity, physics, electron gas model
Supplementary material for this article is available online
1. Teaching with digital support
Increasing digitalisation in the school system
gives access to a wide variety of didactic mater-
ial. The integration of these digital teaching
materials, videos or simulations gives teachers
completely new possibilities for designing their
lessons which in turn has an effect on the per-
formance of the learners [1–4]. One techno-
logy that is receiving more and more interest in
teaching is augmented reality. AR makes it pos-
sible to easily visualise processes that otherwise
would not be feasible to demonstrate. Real objects
or experiments can thus be digitally augmented
for a better understanding of difcult details or
processes.
1.1. Augmented reality in physics education
In the context of classifying AR according to
immersion [5], it is important to note that in our
understanding any AR experiment necessarily has
to involve a physical experimental setup. Phys-
ical objects should not be replaced by virtual,
computer-generated visualisations which other-
wise are non-perceptible. All elements should be
displayed as a genuine augmentation of the real
experiment.
International studies describe various bene-
ts of AR-supported learning environments
[4,6]. Two meta-studies report positive effects
on cooperation in groups, motivation, and the
development of spatial imagination in students
especially in STEM (science, technology, engin-
eering and mathematics) subjects [6,7]. Accord-
ing to Wu et al [8], making the invisible visible
is a decisive advantage of AR and according to
Radu [7] a newly learned subject can be anchored
in the memory for a longer period of time and
allows to better illustrate spatial structures and
processes. Altmeyer et al [9] found higher scores
in conceptual knowledge (with the same cognitive
load) for an AR-supported laboratory task in an
electricity teaching setting. The additional cog-
nitive load or the non-intuitive user interfaces of
the applications paired with the lack of digital
competences of the learners are the main adverse
effects described of AR [6,7].
Teaching physics is usually based on a two-
step process in which a theoretical model is intro-
duced on the basis of the outcome of a real exper-
iment. The advantage of AR is the ability to
overlay the theoretical model, or representations
thereof, directly onto the real experiment, creat-
ing a visual link between model and reality (e.g. a
magnetic eld line model around a real magnet
that can be moved by the student). In addition,
time-dependent or three-dimensional movements
(e.g. in the current ow model) can be visualised
while the students interact with the setup. As a
consequence, they receive instantaneous (digital)
feedback during experimentation (see [3]).
Currently only a moderate number of AR
apps are available for enhancing education in the
eld of physics. For example, an app developed
in 2013 shows digital magnetic eld lines of a bar
magnet [10]. The HoloLens was used to visual-
ise the thermal ow in heat conduction [11]. In a
different realisation, the image of a correspond-
ing theoretical model is superimposed on selec-
ted physical experiments via the use of Geogebra
[12].
However, most of the existing AR-
application examples do not go beyond an exem-
plary character.
1.2. Analogies used in teaching electricity
An important and often difcult eld in the school
physics curriculum is electricity. In the rst half of
secondary school, many lessons are spent teach-
ing students the basic electrical concepts (electric
current, voltage, resistance) and the understand-
ing of simple electric circuits (series and parallel
connection). Since e.g. the electric current cannot
be perceived directly the subject is very difcult
for the students and many of them retain common
misconceptions about electricity after these intro-
ductory lessons [13]. In teaching electricity, the
understanding of students depends heavily on the
July 2022 2Phys. Educ. 57 (2022) 045024

Experiments for students with built-in theory: ‘PUMA: Spannungslabor’
analogy being used to explain the movement of
the charge carriers. Well-known analogies include
the water analogy with open or closed pipes or the
bicycle chain analogy (see [14]). These analogies
have been adapted already into an AR application
which shows a visualisation of the analogy over-
laid on top of a circuit built out of modular blocks,
changing the visualisation according to the pre-
vailing potential or the electric current strength
[15].
In recent years, a new theoretical analogy
called ‘electron gas model’ [16–18] has been
developed which shows greater success in redu-
cing misconceptions compared to the previously
mentioned analogies. For an overview of the
model assumptions and their possible uses in
the classroom, see the following article, which
is freely available online [19]. This analogy had
not yet been adapted by AR applications. Since
all analogies based on the electric potential, as
compared to analogies based on the electric cur-
rent, were particularly conducive to learning [16],
the electron gas analogy attempts to build on this
and draws parallels between the air pressure and
the electric potential as ‘electric pressure’. In the
model, a ow of electrons from one place to
another is always caused by a pressure difference
between both places. Both the atmospheric pres-
sure and the electric pressure are represented by
an intuitive colour scheme in order to support the
development of a well-founded understanding of
the basic electrical concepts and the processes in
closed circuits.
2. The application ‘PUMA:
Spannungslabor’
The AR app visualises the basic electrical con-
cepts which are modelled in accordance with the
electron gas analogy by overlaying it virtually
onto a physical experimental kit. The application
superimposes moving virtual electrons represent-
ing the electric current and coloured overlays
indicating the electrical pressure atop the conduct-
ing pieces in different colours. The visualisation
can be inuenced by the user to make it suit the
augmented experiment. To do this, the user can
choose to display or hide virtual objects by tap-
ping corresponding buttons on the right and left
side of the app interface.
Figure 1. Experimentation kit.
The basis of the experimental setup is a cir-
cuit board with three open parallel slots and three
additional open slots, which can be connected in
series (see gure 1). The gaps can be lled with
a variety of components including different elec-
trical resistors, light bulbs, short-circuit plugs or
switches. The user is free to choose which com-
ponent to install where. Additionally, the template
board contains slots for voltage sources in form of
battery blocks or external power supplies.
For identication and tracking purposes, the
components were labelled with QR codes. The
programming of the application was done in the
Unity engine in conjunction with the Vuforia
extension for recognising the QR codes. The
image recognition is integrated into the app. For
the application to work, all codes have to be
scanned rst, starting with the base target. If the
base target is detected, a green checkmark appears
in the centre (see gure 2). Then, red boxes are
displayed to indicate where a component could
potentially be added. Upon successful detection of
a component in one of the designated spaces, e.g.
a light bulb or a switch, the boxes colour changes
to green.
After nishing the setup procedure, the
visualisation can be started by pressing the
‘Play’-Button in the lower right-hand corner
(see gure 2). The app then calculates the correct
electrical potentials and currents for the circuit
based on the position and characteristic values of
the components (see gure 3).
The app can be applied to almost any experi-
ment related to simple electric currents and can be
used both for experiments performed by teachers
in front of the class and for experiments performed
July 2022 3Phys. Educ. 57 (2022) 045024

C Stolzenberger et al
Figure 2. Screenshot of the setup procedure. By scan-
ning the QR code displayed, you can access a short
video showing the scanning process.
Figure 3. Screenshot of the visualisation the app
displays.
by students themselves in discovery-based learn-
ing settings.
To use the application in teaching, educat-
ors have to simply install the application and
print out and tape the targets to the corresponding
components of their experimenting kit. The les
and instructions for that will be presented in the
application. The app itself is available for iOS and
android devices via download from the respective
app stores.
2.1. Application functionalities
One important function of the app is certainly the
ability to display electrons. They are represented
by white spheres (see gure 3).
According to the electron gas model [16], in
the visualisation of open circuits, the average dis-
tance between these spheres depends on the elec-
trical pressure (i.e. the electrical potential) at the
respective location as described above. In a closed
circuit the electrons move along the conducting
components. To avoid potential dependent drift
velocities, the displayed spheres now are equally
spaced and their speed is directly proportional to
the electric current.
At nodes the electrons split up according to
the resistance of the components in the paral-
lel circuit. The visual gaps resulting from the
few electrons shown (compared with reality) are
minimised by an algorithm that splits the elec-
trons as homogeneously as possible. In addition,
a small electron-electron repulsion is introduced,
which restores the uniform distance between the
electrons.
The conductive elements can be coloured
according to the prevailing electrical pressure.
Red represents a low electrical pressure, blue a
high one [20]. Yellow corresponds to a neutral
pressure, which is equivalent to electric ground.
When connecting a battery, it is assumed that the
battery terminals are at a symmetrical potential
around zero/ground. The minus pole of a 4.5 V
battery is accordingly at −2.25 V (with the plus
pole at +2.25 V). This scale is also displayed in
the upper right-hand corner, while using this mode
of visualisation.
As mentioned earlier, the visualisation of the
electrons and the colouring of the areas accord-
ing to the electrical pressure can be separately
switched on and off by the user. This gives the
students the opportunity to concentrate on either
the current or the voltage aspects of the circuit
while experimenting thus reducing the extrinsic
cognitive load by reducing the amount of unne-
cessary information being displayed, according to
the coherence principle [19]. In case of a parallel
circuit, for example, it may be more interesting
to view the division of the current at the nodes,
while in case of a series circuit, viewing the elec-
trical pressure may be the focus due to the differ-
ent pressure in the areas between components.
To investigate the interaction of the elec-
trons within the various components in the circuit,
additional visualisations can be displayed (see
gure 4). For this purpose, the two-dimensional
microscopic model of electric resistance used in
the teaching concepts for the electron gas model
[16] was transferred to three dimensions. In this
model, electrical conductors are characterised by
a uniform arrangement of the immobile ions of the
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Experiments for students with built-in theory: ‘PUMA: Spannungslabor’
Figure 4. Visualisation of a conductor (top) and a res-
istor (bottom).
metal, while non-negligible resistances are rep-
resented by an uneven arrangement of ions. As a
result, there are more collisions between the con-
duction electrons and immobile ions in the latter
which leads to a higher resistance according to
the Drude model. This model for describing elec-
trical resistance, in which the resistance is determ-
ined by local electron-ion-interaction [16], is also
extended to describe the processes in a light bulb.
There, collisions between electrons and ions addi-
tionally result in an increase of the oscillation
amplitude of the ion. The oscillation returns to its
initial state after a random period of time by emit-
ting a light particle.
To feature semi-quantitative investigations,
an option was added which displays values for the
resistance, current ow and voltage drop at each
component. Of course, these values are not meas-
ured but rather calculated from the known data of
the components read in via the QR codes.
During development, both the design and
content of the application were evaluated by 14
physics teachers in total, ensuring correct present-
ation and usability in the classroom. In addition,
the app has been used with school classes in
teaching experiments. The responses from both
teachers and students were positive. A larger-scale
study on the use of the app in learning settings is
planned for the near future.
After starting the app, the user can choose
between getting brief handling instructions and
selecting different operating modes. According to
the teacher’s instruction, the students pick one of
the modes and start the AR-part of the application.
The modes have different levels of complexity so
that visualisations of topics not yet discussed in
class can remain hidden.
In a separate menu the user is able to set some
so-called ‘model parameters’. It allows to vary
the size and distance of the virtual electrons from
each other depending on the potential. This gives
learners the opportunity to reect on the nature of
theoretical models. It facilitates the understand-
ing of the fact that the number and position of
the electrons displayed are only determined by the
respective model parameters and do not corres-
pond directly to reality. On the other hand, it can
be discussed that each setting, e.g. the denition
of the current intensity as charge per time, must
be correctly represented in the model.
A further step planned for the development is
the implementation of an interface to offer the pos-
sibility of connecting Bluetooth multimeters to the
application and thus displaying values measured
directly during experimentation. This would allow
the app to accurately enhance an experimental
setup using external power supplies instead of bat-
tery packs.
The observation of an open circuit is espe-
cially interesting since it is possible to observe
how the voltage attached to an electrical conductor
changes the distance between the electrons (see
gure 5).
2.2. Usage in classroom
The application can contribute to topics like the
introduction of electrical pressure as the cause of
electric currents, the development of the concept
of the electric current, and qualitative observations
of various types of resistors, both ohmic and non-
ohmic. Furthermore, the application can analyse
simple circuits of up to three resistors, both in
parallel and in series, and it can augment semi-
quantitative experiments referring to Ohm’s law.
As mentioned above, both teachers and stu-
dents can make use of the app in physics les-
sons. In our opinion, it is particularly suitable for
students as it allows them to make and observe
changes in the experimental setup which are not
observable otherwise, going beyond changes in
the brightness of lamps or the numbers on a meas-
uring device. They can identify changes in cur-
rent strength directly (represented by the move-
ment of the electrons) or literally see the electrical
July 2022 5Phys. Educ. 57 (2022) 045024

C Stolzenberger et al
Figure 5. Electron density difference in an open circuit
without a voltage source (top) and with a voltage source
(bottom).
potential via the visualisation of the theoretical
analogy (represented by colour). Thus, students
are given the opportunity to strengthen or disprove
their own conceptions about electricity.
One particularly instructive example is a
simple circuit of two light bulbs, where one of
the bulbs can be bypassed by closing a switch
(see gure 6). Without augmentation, closing the
switch changes only the brightness of the light
bulbs (in addition to changes in abstract measure-
ment values). However, the app intuitively shows
that the electrons, previously moving through the
lamp, now move through the closed switch. Addi-
tionally, the closing of the switch changes the
electric potential from three distinct regions of dif-
fering electrical potential (coloured blue, yellow
and red) to two, one of which surrounds one of
the light bulbs. By eliminating the voltage drop
on this lamp, it stops glowing. With this, the
change in the bulbs’ brightness is much easier to
understand.
The examples mentioned above illustrate how
the implementation of the application in school
Figure 6. Augmentation of an experiment where one
of two light bulbs can be bypassed by closing a switch
(top: open switch; bottom: closed switch). By scanning
the QR code displayed, you can access a short video
showing the experiment.
teaching can change lessons from a lecturing style
into a more collaborating and discovery learning
style.
3. Conclusion and perspectives
The app ‘PUMA: Spannungslabor’ can be util-
ised in teaching almost the entire basic electricity
theory at school. In principle, the app allows stu-
dents to simultaneously make experimental obser-
vations and explain them with the corresponding
theoretical analogy overlaid on top of the experi-
mental setup. This includes qualitative statements
about the various basic electrical concepts in open
and closed circuits as well as semi-quantitative
measurements leading to the understanding of
Ohm’s law. The app also allows teachers to
address the validity and visualisation of theoret-
ical analogies using the electron gas model as an
example.
For more information about the app
and its implementations see our website:
July 2022 6Phys. Educ. 57 (2022) 045024

Experiments for students with built-in theory: ‘PUMA: Spannungslabor’
www.physik.uni-wuerzburg.de/pid/physik-
didaktik/augmented-reality/puma-spannungslabor
The app is available for free in the app stores.
Data availability statement
No new data were created or analysed in this
study.
Funding
This project is part of the ‘Qualitätsoffensive
Lehrerbildung’, a joint initiative of the Fed-
eral Government and the Länder which aims to
improve the quality of teacher training. The pro-
gramme is funded by the Federal Ministry of Edu-
cation and Research. The authors are respons-
ible for the content of this publication and grant
number: 01JA2020.
Received 9 December 2021, in nal form 10 March 2022
Accepted for publication 24 March 2022
https://doi.org/10.1088/1361-6552/ac60ae
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Christoph Stolzenberger studied
physics and completed his doctorate
in physics didactics. He works as a
mathematics and physics teacher at
secondary school and as a research
assistant at the chair of Physics
Education at the University of
Würzburg. His research interest is
in the development of augmented
reality applications and their potential
use in the classroom.
Florian Frank is a research assistant
at the chair of Physics Education
at the University of Würzburg.
His research focuses on the use of
augmented reality for supporting the
development of correct mental models
of electricity in students. As part of
his PhD-project, he will evaluate
the App presented in this article in
learning settings with secondary
school students.
Thomas Trefzger graduated in
physics and completed his PhD
Thesis in experimental particle
physics at the University of Freiburg,
he worked at LMU in Munich, where
he nished his habilitation in 2001.
Since 2007 he is full professor
and holder of the chair of Physics
Education at the University of
Würzburg.
July 2022 8Phys. Educ. 57 (2022) 045024