Experiments in Electricity and Magnetism for Future Teachers: From Lectures to Teaching Labs

The paper reports on an improved approach to pre-service physics teacher training in electricity and magnetism at our faculty. This training starts with an experiment-based lecture in the first year, complemented by an optional seminar that emphasizes experiments students will be able to use in their future teaching. Three years later, it culminates in teaching labs dedicated to this field. The motivation for changing the previous traditional teaching of this topic, the important features of the current state of the art, and the lessons learned are presented. All this is illustrated by a number of examples of experiments that have proved useful and attractive to students.


Introduction
The course Electricity and Magnetism in the first year of the Bachelor's degree program for future physics teachers at the Faculty of Mathematics and Physics of Charles University is a traditional one.Nevertheless, for many years it was perceived by students as quite demanding.From the very beginning it relied on math (with grad, div, curl, etc.) and though it was accompanied by demonstration experiments, the topic seemed to be rather abstract to students.(This was clear both from the results of the students' survey done at our Faculty and from informal discussions with students.)Moreover, we found that while students could finally calculate solutions to formal problems, they often failed to answer simple conceptual questions, let alone perform experiments by themselves.
Therefore, more than a decade ago, we tried to supplement the course with an optional seminar called "Electricity and Magnetism Step By Step".It was appreciated by students as beneficial, see [1].However, the problem with lectures being perceived as difficult remained.
In the Master's degree program for future physics teachers, a special lab "Practical Course in School Experiments II" focusing on experiments in Electricity and Magnetism for upper secondary school has always been a standard part of teacher training.Nevertheless, its content gradually became a little bit outdated.
These shortcomings motivated us to try to make teaching of this topic more accessible and attractive for students.In the following, we describe how all three subjects mentioned above evolved, how they are now perceived by students, and what experience we gained.We also present some of the experiments performed in our courses.In addition to illustrating our approach, they show the different roles that experiments play in our lectures, seminars, and labs.Since it is not the purpose of this article to give detailed instructions, the experiments are described rather briefly, but often with references that provide further information.

Experiments are key elements of lectures and seminars
It is clear to physics educators (and science educators in general) that experiments, especially practical work done by students, are an important part of their learning process.(See, e.g., [2]; for current views of physics educators, see [3].) Therefore, in the improvement of the subjects mentioned above, physics experiments played a crucial role.

Lectures
The department, which supports demonstration experiments in a lecture hall in our faculty, offers about two hundred demonstration experiments.From these, some 30 were chosen for the lecture for future physics teachers -especially those requiring special equipment (e.g.jumping aluminium ring on a large coil, Tesla transformer or demonstration of motion of electrons in a magnetic field).
Along with such experiments traditionally used in the lectures, more than one hundred experiments with simple tools were newly developed/adapted for the lecture.These experiments served several purposes.Firstly, they not only demonstrate the physical phenomena but are often used to introduce relevant topics and concepts.Secondly, they illustrate that to investigate electricity and magnetism one need not use just sophisticated equipment, but even quantitative measurements can be done by everyday objects and tools.Thirdly, these experiments are more hands-on than large experiments using special equipment.Last but not least, these are experiments, students will be able to use in their future teaching physics at schools.To give some idea about such experiments we can mention a few examples; others will follow in section 3.
To introduce Coulomb's law not just by speaking about the historical experiment a simple tool with plastic straws can be used; see [4].(Or [5], where also other simple experiments are presented.) To measure how a magnetic field from a dipole (a small magnet) decreases with distance, a smartphone can be used; this experiment was briefly described in [5]; various simple experiments with permanent magnets were described in [6].A smartphone can also be used to measure the magnetic field around a wire with current; this was used as a starting point to "derive" Ampère's law.
Damped oscillations in an RLC circuit can be demonstrated without any special sensor using a common notebook with a soundcard using the Soundcardscope software.Also, frequency characteristics of RC high-pass and low-pass filters can be investigated by a notebook using Soundcardscope; qualitatively, students can "see" their effect by hearing music going through them.
Many experiments can use small LEDs.For example, two antiparalelly connected LEDs can indicate AC current (moving such pair of LEDs shows that the voltage in mains is AC, of course, the voltage is transformed to several volts only), show that there is energy in a charged capacitor; model of Graetz rectifier can show the principle of its function (when the frequency is small), etc. ( [7]).

Optional seminar called "Electricity and Magnetism Step By
Step" In the seminar, students, future physics teachers, themselves perform simple experiments that can be used in teaching physics at the lower (and also upper) secondary school level.This serves a double purpose: Firstly, the students perform experiments they often just saw in school (when attending lower and upper secondary schools) and forgot or, in a worse case, have not seen at all yet.(It turned out that for some students, the seminar was the first opportunity for practical experiments, such as wiring a simple electrical circuit, lighting an LED with a simple dynamo, etc.) So, students learn or re-learn physics by doing it in an inquiry-based style, working in small groups, and discussing experiments, their meanings, and results.It is important that they do this in a safe environment where they are not blamed for errors, misconceptions, false opinions, etc.They are not tested for "what they should know already"; errors are chances to improve conceptual understanding of the topic.
Secondly, by their own experience, they naturally learn how electricity and magnetism can be taught in an inquiry-based style starting from experiments.We consider this quite important because, as it is often stated, teachers teach in the same way they were taught.This, of course, should be reflected in their pre-service training.(This view is shared by a physics education community; see for example, point 4.1 in [3]: "Teachers should be taught the way they are expected to teach.")During the seminar, students see the specific teaching-learning sequences that proved to be useful, discuss misconceptions and how to disprove them, etc.
There is also another point why the seminar is helpful.Although most of the experiments used here are at the lower secondary school level, connections to university-level physics taught at lectures are discussed from time to time.This helps to build bridges (or, rather, to destroy barriers) between physics at the university and the secondary school level.Of course, we try to build such bridges also at lectures, but at the seminars, they are built "from the bottom up", so the efforts at lectures and seminars are complementary.The connection between lectures and the seminar is also supported by some simple experiments mentioned above in part 2.1.; in the seminar, we can discuss in more detail how they can be used in teaching and learning etc. (Adding these simple experiments to the seminar also proved to be useful when the lecture was led by another person than one of the authors of this paper, in which case the style of the lecture was a bit different.)Some details concerning the seminar can be found in [1].The overall approach to teaching in the seminar is based on the informal "Heureka" project aimed at in-service physics teacher training, see [8].The project has been in existence for about thirty years, has influenced several hundred teachers, and is still ongoing.

Practical Course in School Experiments
The Practical Course in School Experiments has also undergone a transformation in recent years (see [9]).Nowadays it offers a variety of experiments -from very simple ones with tools that our students (and their future students in schools) have at home, to more complicated apparatus.Our goal was to enable students to perform and master different types of experiments -student, demonstrations, lab work, home projects, etc. Students now meet a wide range of experiments, from which they can choose later in their careers when teaching physics in schools.Also, experiments to help students overcome their misconceptions and improve their conceptual understanding were added to the seminar.
Another goal was to develop students' skills in how to conduct experiments and how to solve technical problems -for example, some of them changed a fuse in a multimeter for the first time in this seminar.The seminar provides an opportunity for them to get a routine when performing experiments, to be sure which specific equipment to use for a given experiment (for example, a coil with how many turns), to master the situations when something does not function properly, etc.
Yet another aspect of the seminar is important: methodical discussions on experiments in teaching physics at schools are a natural part of it.They include discussions about why to use such and such experiments, in what way, in what order, how to ensure safety, how to introduce a particular experiment to pupils, to what to bring their attention, etc.
Practical Course in School Experiments is a compulsory seminar.So even the students who have not attended the Electricity and Magnetism Step By Step seminar (either because it is optional or because they have studied a bachelor's degree in another study program) have to go through it -and learn simple experiments they otherwise could miss.It lasts for one term, 4 hours per week, and students perform several tens of experiments on each topic.So the seminar provides an excellent opportunity to prepare future physics teachers for their teaching in schools -and students appreciate it (see further in part 4 of this paper).The seminar is compulsory also for teachers from schools who extend their teaching qualification to physics (and is also appreciated by them).

Examples of experiments for selected topics -from Lectures to the Practical Course
Even for the same topic, the experiments in lectures and two above-mentioned seminars are not blindly repeated.Some of them stay the same, of course, but because experiments serve slightly different purposes in lectures and seminars, it is natural to use various experiments and equipment.We illustrate this with four examples.

Electrostatic induction, two types of charge
In lectures, electrostatic induction is used for example when the method of images is mentioned.A charged plastic straw below a metal plate (held by a hand, so roughly at a potential of the ground) is attracted to the plate and jumps to it when it is sufficiently close, see figure 1. (The distance is about half of the distance in which one charged straw floats above another charged straw.The straw is attracted by the metal plate by the same force it would be attracted by the oppositely charged image.) Figure 1.Experiment illustrating the method of images.A charged straw is attracted by a conductive plate.

In the seminar "Electricity and Magnetism Step By
Step", electrostatic induction is demonstrated and its principle is discussed, in an inquiry-based style, using a simple experiment with a large metal can, see figure 2. Here, the students themselves should think about what is going on in each step of the experiment.(When a negatively charged plastic rod is placed inside the can, negative charges in the can are at its outside surface.When we touch the can, these negative charges go away.So the result is a positively charged can.A piece of aluminium foil at the outer part of the can indicates how the can is charged.)In the seminar "Practical Course in School Experiments" students demonstrate two types of charge appearing on the plastic rod when it is rubbed by different cloths (one of which may be Teflon) by using a charge meter, see figure 3.

Ohm's law and electric circuits
In lectures, of course, experiments are carried out to show for which components Ohms's law applies and for which it does not (light bulbs, LEDs, …).
Also, a simple "puzzle" (a problem task) is presented to students with components at which Ohms's law is surely valid.A voltage divider with two 1 kΩ resistors divides the voltage of, say, 4.5 V into one half, i.e., it provides about 2.25 V at the output.This can be checked by measuring the voltage with a common multimeter.However, when we use a divider with two 10 MΩ resistors, which surely should divide the voltage also into 1:2, the multimeter will show just about 1.5 V, see figure 4. It proved to be a good point for starting a discussion on the internal resistance of a multimeter, the influence of a measuring instrument on measured objects, etc.

In the seminar "Electricity and Magnetism Step By
Step", students deduce the behaviour of electric circuits from water models (see figure 5) and compare their prediction with measurements.In the seminar "Practical Course in School Experiments", students measure the current-voltage characteristic of both resistors and light bulbs using digital sensors.Measuring the characteristic of a light bulb is used as a problem task which raises questions students discuss: Why is the characteristic GIREP-2022 Journal of Physics: Conference Series 2750 (2024) 012015 non-linear?Of course, students at this level know the explanation based on the temperature of the filament.However, taking it as a plausible hypothesis, further (pedagogically more important) questions follow: How can we test such a hypothesis?How to design and perform experiment testing it?A nice straightforward experiment testing this hypothesis involves measuring the characteristic when the glass is removed, and the filament is cooled by water (see figure 6); the characteristic is linear in this case.
Figure 6.Current-voltage characteristic of a light bulb the filament of which is cooled by water is linear.For some details, see [9].
Of course, other issues related to the experiment are also discussed: What is the resistance of the light bulb determined from the current-voltage characteristic?As the light bulb for 230 V is used, the resistance can also be calculated from the input power written on the bulb.Students should explain why these two values of resistance differ considerably.The experiment is described in detail (including pedagogical notes) in [10].

Oersted's law
In lectures, small neodymium magnets close to the wire can show the direction of the magnetic field even for small currents, see figure 7.

In the seminar "Electricity and Magnetism Step By
Step", students investigate the magnetic field around a wire with current using a compass, see figure 8.They switch on and off the current and observe the deflection of the compass needle for the wire above and below the compass.The polarity of the battery can be changed too, of course.In the seminar "Practical Course in School Experiments" students learn how to show the shape of magnetic field lines near a wire and in a solenoid and toroid using iron fillings, see figure 9.They also learn that quite a large current (for example, 20 A) is needed, knowing technical details like this is important for their future teaching in schools.The experiments are freely available on the web ( [11][12][13], for now only in Czech), so that not only our students but also teachers from schools can show the results to their students in case they do not have sources providing sufficient current in their schools.

Electromagnetic induction
In lectures, a simple indicator with an operational amplifier and LEDs was used to demonstrate the voltage induced in a conductor moving in a magnetic field, see figure 10; even the Earth's magnetic field is sufficient if the wire is approximately one meter long.(Students or teachers can build such indicators themselves; it was proved in a workshop for physics teachers and in a lab for students.)

In the seminar "Electricity and Magnetism Step By
Step", students investigate electromagnetic induction for example using a coil, a magnet, and a simple indicator with two LEDs, see figure 11.In the seminar "Practical Course in School Experiments" students learn to use various experiments concerning electromagnetic induction using diverse equipment, for example: a coil in a nearly homogenous magnetic field, an induction cooker, and a wireless charger for mobile phones; see figure 12.A more detailed description of the first experiment can be found in [4], some details of the other two experiments in [9].

How it evolved -and experience gained
The new approach to the lectures, seminars, and labs evolved for years.The seminar "Electricity and magnetism step by step" started more than fifteen years ago, the new approach to lectures about six years ago, and labs were innovated five years ago.The changes were not one-time; teaching materials were created subsequently (and reviewed by members of our department), and the courses and their cooperation slightly evolved reflecting the experience.
In developing and implementing the changes we were guided by both our own experience, feedback from students, and surely also by inspiration from other resources, including inspiration from GIREP and other conferences.However, no particular paper or approach was decisive or guiding for us, apart from a general IBL approach and "spirit of the times" in the physics educational community.(That's also the reason why the list of references below is rather restrictive; it would not be fair to cite the works of just a few authors, no matter how relevant to changing teacher training or new approaches to physics teaching and learning.The influence of all this on us was really a general one.) The changes in lectures and teaching labs were appreciated by students.This can be documented by the results of a formal survey conducted after each term at our faculty and by more informal feedback from students.As for formal feedback from the survey we can state that on a four-point scale, 1-4 (1 being the best), the average mark for courses mentioned above is typically between 1.0 and 1.3.(The numbers of students, prospective physics teachers, are rather low, usually under 20 in a year, sometimes even under 10, and not all of them respond to the survey, so we do not present any statistical treatment of the data here.)Examples of students' statements in the survey are given below.Informal feedback gained from discussions with students confirms the good ratings from the survey.
The optional seminar Electricity and Magnetism Step by Step now need not supply clear explanations of parts previously perceived as very difficult in lectures -this enables us to focus more on what students could use in their future teaching.Both aspects are reflected in students' feedback: "This is a very interesting seminar that helped me to connect theory with practice.In this seminar, you really learn by experimenting on your own in a relaxed, friendly atmosphere.""This course will give future teachers a great insight into how to teach physics in an interesting way in elementary school.I enjoyed it from beginning to end."That the seminar is attractive and useful to them is supported by the fact that although it is voluntary, it is attended by most of the students.
The survey about the seminar Practical Course in School Experiments shows that students appreciate especially the opportunity to try a broad range of experiments, and the willingness of course leaders to explain everything and to share their own experience from teaching in secondary schools.To quote some students' feedback: "One of the most useful courses for future physics teachers, sophisticated selection of experiments, often transferable to the classroom with minimal acquisition costs, well-prepared materials.""It is clear that both teachers have had many years of experience in their own teaching, perfectly explain everything, and have a very friendly approach to students." Experiments in lectures were performed even during online teaching, which was necessary due to covid restrictions, though to a limited extent and only as demonstration ones.(It turned out that simple experiments could be done at home when the lecturer was lecturing from home.Students also valued it: "I appreciate the quality of the lecture, in which the lecturer managed, despite the difficulties of distance learning, to include interesting experiments and examples from practice.")Seminars and a special lab were organized in a block form during periods when teaching in university buildings was possible -of course, in this case, direct contact with students was necessary.

Conclusions
The electricity and magnetism part of our faculty's training of future physics teachers has evolved in recent years into a form that reflects the needs of both the courses and students.In lectures, seminars, and labs, experiments are now a key ingredient in teaching and learning.
Although according to our experience, the current form of the above-mentioned lectures, seminars, and labs works well, we are still "tuning" them, adding new variants of experiments, and developing teaching materials.
For example, during covid times, nearly 250 pages of teaching materials for Electricity and Magnetism lectures were created and put online; yet this still should be augmented.Also, materials for the seminars Electricity and Magnetism Step by Step and Practical Course in School Experiments are on the web for students -and for teachers from schools too, the access to the materials is not restricted.Unfortunately, all these materials are in Czech only, so the general reference [14] will not be very useful for most readers of this paper.However, at least the description of a few experiments in English (12 experiments from more than fifty that are described in Czech) can be found in [15].Further experiments will be added in the future.

Figure 2 .
Figure 2. Experiment with a can for thinking over details of electrostatic induction.

Figure 3 .
Figure 3.A charge meter is used to demonstrate two types of charge on the same rod rubbed by different cloths.(The charge is negative when the rod is rubbed by ordinary cloth, positive if rubbed by Teflon cloth.)

Figure 4 .
Figure 4.A simple puzzle with voltage dividers.

Figure 5 .
Figure 5. Deduction of the behaviour of an electric circuit from a water model.

Figure 7 .
Figure 7. Small neodymium magnets are used for demonstrations of Oersted's law.(A piece of paper showing the orientation of the magnet is perpendicular to its axis.The photo is taken from above.The current is controlled by the number of light bulbs connected in the circuit; in the left photo the current is zero; in the right photo it is maximal.)

Figure 8 .
Figure 8.A compass shows the direction of a magnetic field near a wire with current.

Figure 9 .
Figure 9. Magnetic field lines are visualized by iron fillings.

Figure 10 .
Figure 10.A simple indicator can show electromagnetic induction in a moving piece of wire.A voltage of a few mV is indicated by LEDs.

Figure 11 .
Figure 11.A coil, a magnet, and two antiparallel LEDs can serve for the investigation of electromagnetic induction.

Figure 12 .
Figure 12.Experiments concerning electromagnetic induction: The voltage induced in the coil moving around a magnet is indicated by a multimeter; a small light bulb indicates the voltage induced above the induction cooker and the LED indicates the voltage induced in the coil above a wireless charger.