Virtual physics laboratory for distance learning developed in the frame of the VccSSe European project

Transcription

1 Virtual physics laboratory for distance learning developed in the frae of the VccSSe European project W. Tlaczala 1*, M. Zareba 1, A. Zagorski 1 and G. Gorghiu 1 Faculty of Physics, Warsaw University of Technology, Koszykowa 75, Warsaw, Poland Autoatics, Inforatics and Electrical Engineering Departent, Valahia University Targoviste, 18-4 Unirii Blvd., Targoviste, Roania This paper presents a set of five reotely controlled siulated physics experients accessible via the Internet. They are devoted to gases laws, the heat transportation and the electrical resonance. They have been elaborated by using LabVIEW graphical prograing. With its Reote Panel the LabVIEW applications can be turned into a reote laboratory. Users can open a link with their web browser to a reote application, to control it using the Reote Panel, observe how an experient runs and collect experiental data. Experients devoted to gases laws base on coputing data using theoretical forulas, the other experients are elaborated in full analogy with the real one perfored in the laboratory in the Institute of Physics of the WUT and base on real data acquired earlier in the real experients. This kind of experients can be useful for distance learning using the internet. Keywords distance learning; reote laboratory; Socrates Project; Coenius.1; VccSSe; LabVIEW 1. Introduction A reote laboratory is defined as a coputer-controlled laboratory, which can be accessed and controlled externally through soe counication ediu, for exaple, trough the Internet. The laboratory presented in this paper laboratory is very well prepared to realize such idea. As a rule, university laboratories have well organized real laboratories but, for instance, secondary level schools are usually devoid of real experiental equipents and pupils learn selected subjects fro books only. It was the ai of our work to invent virtual laboratory with siulated experients, which is soething interediate between real laboratory and its virtual equivalent with real experients reotely accessible. Most of work done up to now concentrates on siulation ethods or focuses on distance learning, creating links via internet with real laboratories, situated at universities. We have elaborated a different kind of an e-laboratory, which contains siulated experients based ainly on results obtained in real easureents perfored earlier in the student laboratory, at the Faculty of Physics of the Warsaw University of Technology. The reote access via Internet to real laboratory is usually liited to the period of tie, when the real experients are supported by the laboratory technician staff. For reote users, who want to perfor easureents in different but convenient for the tie, we developed siulated experients, which are equivalents of the real experients and can be available 4 hours a day on the Internet, without any technical support, by connecting the reote PC to the LabVIEW server installed in our lab.. VccSSe ain goals The siulated physics experients, presented in this paper, were developed in the frae of the Socrates Coenius.1 European project VccSSe - Virtual Counity Collaborating Space for Science Education. The Project was addressed to in-service teachers training on using virtual instruents in the teaching process of different Science areas (atheatics, physics, cheistry, biology) and to the pupils who benefit by the ipleentation of the virtual instruents in the classroos. The ost iportant activities to be undertaken in the frae of the Project were creating the training odules and organizing the courses for in-service teachers, creating the database for virtual experients, disseinating the project results at local, national and European level. Disseination of the project results is one of the ost iportant activities to be undertaken in the frae of the project during its third years running. One of the ways of realization of this idea was the creating of virtual laboratory with the siulated experients, which could be attepted reotely with the help of the Internet. * Corresponding author: e-ail: tlaczala@if.pw.edu.pl, Phone:

2 3. Virtual physics laboratory for distance learning The ain purpose of virtual experients is to failiarize pupils with physical phenoena without using any special equipent. Due to siulated experients they can work even at hoe at their own speed, repeating the experient as any ties as they need. Such solutions are also highly appreciated by secondary school teachers, who can introduce to their pupils ore sophisticated experients without having access to a real laboratory. In this paper we describe five experients: three devoted to gases laws, one to the heat transportation and the last one to the electrical resonance. The only thing, which is required to perfor a siulated experient, is a popular personal coputer with MS Windows and LabVIEW Run-Te Engine 8.6 (RTE 8.6). After opening virtual laboratory using web browser, and following enclosed instruction, one can download the RTE 8.6, fro National Instruents web site, needed to run experients, and than perfor the independently. 3.1 Gases laws Figure 1 shows front panels of the set of three siulated experients devoted to ideal gases laws: pressure (p) dependency of the volue (V) of a gas at constant teperature (T) Boyle-Mariotte s law given by pv = p V 0 0 for T = const, (1) teperature (T) dependency of the volue (V) of a gas at constant pressure (p) Gay-Lussac s law given by V / T = const for p = const, () teperature (T) dependency of the pressure (p) of a gas at constant volue (V) Charles s law given by p T = const / for V = const. (3) Fig. 1 Front panels of the siulated experients devoted Boyle-Mariotte s law a), Charles s law b) and Gay-Lussac s law c) Perforing experients a user can set as constant one of three paraeters: the pressure (p), volue (V) and teperature (T) and check relationships between two others depending on selected experient. During virtual easureents a user can collect data, place the on the graphs, and fit curves to points placed on the graphs. In the first experient (Fig. 1a) the air colun is aintained at constant roo teperature T. At an external pressure p 0, it has a volue V 0. During experient perforing, the pressure p in the air colun is reduced, and the increased volue V of the air colun is deterined for different pressure values. The experient confirs the relationship (1). In the second experient (Fig. 1b), the theroeter easures the specific teperature of the air in the colun, in which the pressure is constant. This experient easures the volue V of the air colun as a function of the teperature T. The experient confirs the relationship (). In the third experient (Fig. 1c), the pressure p in the air colun is reduced in the way, which allows keep the volue V constant as the teperature drops. This experient easures the pressure p of the air colun as a function of the teperature T. The experient confirs the relationship (3). 468

3 3. Heat transportation In the Heat transportation experient (Fig. ) one easures the theral conductivity coefficient λ for a etallic rod. It has the eaning of the quantity of heat Q transferred through the aterial in unit tie t, with the cross-section S, and unit gradient of the teperature grad T. The relationship between Q and others paraeters is the following: Q = λs(gradt) t. (4) Fig. Front panel of the Heat transportation experient Main goals of this experient perforing are: becoe failiar with therodynaics experient, study echanis of heat conduction in solids, understand the teperature gradient idea, becoe failiar with teperature easureents perfored with RTDs sensors, becoe failiar with easureents, devoted to deterination of the theral conductivity coefficient λ, based on the Ängstro ethod. The value of the theral conductivity coefficient is different for different aterials and characterizes, for instance, the isolation characteristics of aterials. For iron λ = 79 [SI units], for water λ = 0,6 etc. Presented here experient is based on the Ǻngströ ethod and deonstrates the daping of teperature values in a rod. The teperature changes are generated by repeatedly switching on/off the heating syste installed on the one end of the rod. This process produces a teperature wave, which penetrates the rod. These changes propagate through the whole saple, but with the aplitude decreasing (exponentially) with increasing distance x fro the source of heat. The teperature T is then described by a function typical for all daped waves. 3.3 Electrical resonance The current and voltage as a function of the frequency can be observed in the series and parallel tuned RLC circuits. Voltage resonance - serial resonance RLC equivalent circuit diagra for serial resonance is shown in Fig. 3a. In this configuration L denotes the inductance of the inductor, C is the capacitance of the capacitor, and R = R s + R d + r L + r C is the equivalent resistance of the circuit. The circuit diagra is shown in Fig. 3a. The relation between e(t) and i(t) is given by the equation (5) di( t) QC e t) = i( t) R + L + dt C (. (5) 469

4 where e(t) = E cos(ωt) an alternating voltage source, i(t) is the current, Q c is the charge of the capacitor C, r L and r C denote loss resistance of the inductor and the capacitor respectively, R d is a daping resistance, R s - the source resistance. Fig. 3 Equivalent circuit diagras for series electrical resonance a), and parallel electrical resonance b) The absolute value of the total ipedance Z is given by (6a) and the phase displaceent ϕ s between the current and the voltage is given by (6b). E Z = I = R + ωl ωc, S ωl = arctan ωc R ϕ. (6a, b) Current resonance - parallel resonance Figure 3b shows RLC equivalent circuit diagra for parallel resonance circuit. In this configuration R d denotes a dynaic resistance and the resistance R consists of the resistance R s added to the resistance R LEAD. Therefore R = R s + R LEAD. The absolute value of the total LCR d adittance Y is given by (7a), where G=1/R d and the phase displaceent ϕ p between the current and the voltage is given by (7b). I Y = E = ( G) + ωc ωl, P ωc = arctan ωl G ϕ. (7a, b) Fig. 4 Front panel of the Electrical resonance experient 470

5 The virtual experiental set-up (Fig. 4) for resonance phenoena studies siulates the real one, which consists of the function generator, the digital oscilloscope, two digital ultieters (DMM), and RLC circuit. Main goals of the experient are as following: becoe failiar with RLC circuits, understand the operation of the series-tuned circuit, understand the operation of the parallel - tuned circuit, study voltage resonance observed in a series - tuned circuit, study current resonance observed in parallel -tuned circuit, study properties of RLC circuits; resonance frequency f r, phase displaceent φ, Q-factor, bandwidth, loss resistance, and daping. The software used in described siulated experients was prepared in a user-friendly way. Due to the online help reference, that covers the introduction to the physical theory and the usage of software as well, there is no need to have any additional experience to run and perfor the selected experient. 4. Conclusions The exaples of siulated experients presented in this paper show that they can be a very effective support of the teaching process. The ethod that we have elaborated essentially differs fro any others since it is based ainly on real data taken in a real experient. The virtual instruents used in the experients not only allow users to conduct easureents, but also give inforation about physics fundaentals. They instruct a user, a teacher or pupil, how to switch on electronics, how to set correct values of paraeters, run experient, collect and analyze data. This inforation can be selected by pressing the corresponding button available on the top of the front panel of the virtual instruent. Before starting data acquiring, the user has to prepare virtual instruents to work. He ust switch on, for instance, power supplies, digital ultieters, heating and cooling systes. So, presented experients siulate real lab experients perforing, and data acquired in siulated experients are siilar to those obtained in real easureents. Therefore perforing our siulated experient is axially siilar to that perfored in a real laboratory. Acknowledgeents This work was funded through the Socrates-Coenius.1. European project CP RO-COMENIUS-C1: VccSSe - Virtual Counity Collaborating Space for Science Education. The support offered by the Education, Audiovisual and Culture Executive Agency is gratefully acknowledged. References [1] SOCRATES - Progra Edukacyjny Wspólnoty Europejskiej, Inforator, Fundacja Rozwoju Systeu Edukacji, ANPS, Warszawa 004. [] W. Tłaczała, Modeling with LabVIEW, Handbook of Measuring Syste Design, edited by Peter Sydenha and Richard Thorn, 005 John Wiley & Sons, Ltd., pp [3] W. Tłaczała, Virtual Instruentation in Physics Handbook of Measuring Syste Design, edited by Peter Sydenha and Richard Thorn, 005 John Wiley & Sons, Ltd., pp [4] D. Halliday, R. Resnick, J. Walker, Fundaentals of Physics, 001 John Wiley & Sons, Ltd. [5] W. Tłaczała, G. Gorghiu, A. Glava, P. Bazan, J. Kukkonen, W. Mąsior, J. UŜycki, and M. Zareba, Coputer siulation and odeling in virtual physics experients, Proceedings of IV International Conference on Multiedia and Inforation & Counication Technologies in Education. Noveber -5 th 006, Seville, Spain. [6] 471