Joining together theory and practice in the classroom for electrical engineering undergraduates: The large-scale portable laboratory

ABKWH] Electrical engineering teaching requires a combination of theoretical and practical lessons which are, in general, separated for practical reasons. The correct balance between theory and practice is not easy to define and it is a common impression that theory has gained relative weight when compared to laboratory. Laboratory sessions are more expensive than large audience classroom lessons and the group size for laboratory work has to be small. Expensive equipment makes also unfeasible large scale laboratories and laboratory facilities are very often neither appropriate nor comfortable for theoretical lessons. Thus, we describe a proposal to bridge the gap between theoretical explanation or exercises and practical application in a laboratory: the large scale portable laboratory. This temporary laboratory is deployed and collected again in a conventional classroom in few minutes. It allows, with safe voltages and currents, to illustrate and immediately applicate theoretical concepts or to show some phenomena and explain it later by theory in a discovery attitude. This laboratory has some physical limitations (voltages, currents, power, cost and weight of elements) and, by no means, intends to replace practical sessions in a full equipped electric teaching laboratory. It is mainly a tool to connect experimental observations and theoretical explanations during students learning. A complete session with this laboratory will be described and the obtained results will be presented. As a general result, involvement of the students is dramatically increased. Besides this training of students helped in earning time for electric laboratory practical sessions. It also provided good results in a test about the contents of the lesson. Some difficulties such as the preparation time for such mixed theory and practice lessons, and the spent time during the session are also discussed. Introduction and context In Electrical Engineering Education, theoretical lessons and laboratory sessions are generally separated for practical reasons. Laboratory sessions are more expensive than large audience classroom lessons and the group size for laboratory work has to be small. Expensive equipment makes unfeasible large scale laboratories. Besides, laboratory facilities are very often neither appropriate nor comfortable for theoretical lessons. Recently, Judge has presented a very interesting attempt to work in large-scale laboratories for teaching electronic and electrical engineering to first year undergraduate students [1]. But this is not a general practice. As a result, there is an artificial separation between theory and practice which is not suitable, especially for the engineering skills. It is generally accepted that engineering is in its origins a practical discipline but today with a wide content of theoretical contents [2]. Thus, the balance between theory and practice is not easy to define and it is a common impression that theory has gained relative weight when compared to laboratory. This is, however, an artificial separation but it should not be understood as a competition between “theory” and “practice” but rather as a cooperation between both methodologies. For example, Giacaman and De Ruvo describe a strategy to bring together theoretical and practical sessions in the field of programming [3]. Practice is not necessary coming after theory. If a discovery attitude is preferred, practice can be done before theoretical lesson. Or, in a more standard method, students apply or check theoretical concepts during the practical lessons. According to this, the aim of our work is to bridge the gap between laboratory and theoretical sessions by mixing practical lessons in the classroom Of course, presentation of theoretical concepts and rigorous deduction of theories are always required. All the courses shall not be reduced only to practical lessons, but theory is best understood and illustrated if it is immediately connected to a practical experience (as already stated in [4]) or even preceded by practical observations. Teacher’s practical demonstrations in the classroom can help in this task [5][6][7], but student direct experimentation with concepts and practical elements leads to better results in understanding and learning [8][9]. A possible solution is to use computer simulation tools which can be easily introduced in the classroom. In fact, in some Engineering fields, computer simulation of practical situation has taken a dominant place in the practical sessions. These software tools are of paramount importance for students, since they will have to use them in their future, but direct contact with physical experiments cannot be replaced by simulation instruments, especially during the first courses. Our objective could have been achieved with a student’s version of simulation software, but a real practical experience was preferred to reach a mature concept of electrical circuits before using abstract simulation tools. Our work is aimed to second year undergraduates of three different degrees at the Polytechnic University of Valencia (Spain): Civil Engineering, Public Works Engineering (similar to Civil Engineers but with different professional responsibilities) and Chemical Engineering. In all these three bachelor’s degrees, the students are not especially focused on electrical engineering concepts. Besides, in all of them, there has been an important reduction in both the number of theoretical and practical lessons for the electrical engineering teaching. In the case of practical sessions, the reduction reaches in some case 70% and for the theoretical lessons it is close to 50% in all the cases. However, in the last degrees remodeling (2011) the total number of ECTS (European Credit Transfer and Accumulation System) and thus the teaching hours was increased for an equivalent professional qualification in all of these three degrees. Furthermore, some optional courses in electrical engineering were removed from the curriculum. As a result, students have only a four-month course of electrical engineering in their curricula with 24 or 30 hours of theoretical lessons and 7.5 or 8h of laboratory lessons. After this course, no additional electrical engineering course is given to students, even if they pursue to the master degree, in the case of Civil and Public Work Engineering. This context is important for the present work since the relative weight of the electrical engineering has been dramatically reduced as seen by the students (although graduates keep their previous professional responsibilities). That creates a general opinion of secondary importance of electrical engineering learning. Moreover, in these bachelor’s degrees, students are very often not familiar to electrical circuit basis or electricity physics. The residual importance of electrical engineering in the curricula makes difficult for the students to understand the relevance of electrical engineering for their future. Although motivation is of great importance for students success in engineering and electrical engineering [8][10], in our case, it is limited because of: 1) they do not understand why they should study electrical engineering (so different from mechanical engineering, structural calculations, chemistry, etc.), 2) the subject is not connected to other courses in their studies and 3) they are not familiar with electrical concepts. Since, in the short term, it is not possible to increase the total amount of electrical engineering lessons, especially laboratory sessions, we are working on a proposal of mixing theory and laboratory sessions in the classroom by means of the deployment of a portable laboratory in the classroom during the time allocated to the lesson. At the Polytechnic University of Valencia, students normally do not move from one classroom to another for theoretical lessons. They stay at the same classroom and teachers move from one to another. Thus, teachers do not have a specially designed classroom for lessons which always take place in standard classrooms. The proposed solution (what we called the large-scale portable laboratory) for mixing theory and laboratory session in the classroom requires building and collecting an electrical engineering laboratory in a conventional classroom during the lesson. That needs to solve some issues: 1) deployment and collection of the laboratory should need minimum time, typically, less than 10 minutes, 2) laboratory has to be safe, 3) the total weight of the equipment to be moved to the classroom has to be as low as possible, 4) no expensive additional equipment should be needed, only available laboratory equipment such as multimeters, voltage sources or safety cables should be employed. All the parts and procedures of this laboratory will be described as well as a first experience in a classroom and the obtained results. Portable laboratory description The structure of the classroom laboratory is based on the distribution of an individual small low voltage low current source on each table of the classroom. It consists in a small box (10cm × 10cm × 5 cm) with 5 female banana connectors (see figure 1). Depending on the experiment different combination of connectors will be used. For DC or AC circuits the red and black one can be used, for 3 phase circuits the red, black and green will be used for the phases, the blue one for the neutral conductor and the yellow for the ground conductor. Voltage will be kept always below 24V and current limited to some hundreds of milliamps, thus safety requirements are met. The ground conductor in such situations is not really necessary but it helps in teaching to students its importance. Figure 1. Right: individual voltage source (d-sub 9 connectors are on the sides of the box). Left: general distribution box with the protection fuses and the d-sub 9 connectors.