EP0
ASSOCIATION FOR PHYSICS TEACHING
Liceo "Pacinotti", Cagliari (Italy)

The Association for Physics Teaching is a non profit organization operating with the aim of improving physics education and to better the standard of scientific culture in Italy.
To achieve such aims the A.I.F. carries out any suitable activity and, in particular, prints and disseminates publications on cultural and educational subjects and organizes meetings, conferences and training activities for teachers.
49 units have been set up in different places of Italy which operate locally by organizing teachers training courses, seminars, exhibitions, etc. An AIF Unit constitutes a reference point for physics teachers living in its area of activity.

EP1
LA FISICA NELLA SCUOLA
Association for Physics Teaching Journal
L. Brasini, Editor (Italy)

La Fisica nella Scuola (LFNS) is the quarterly journal of the Italian Association for Physics Teaching (AIF). It is supported by membership fees, by subscriptions made by the Ministry of Education on behalf of schools. It is distributed to members of AIF and is not sold independently.
Principal aims are:

1. improving the teaching of physics in high schools;
2. improving science teaching in primary and middle schools;
3. helping physics teachers keep up to date;
4. promoting exchange of experiences in educational research;
5. promoting the dissemination of new teaching methods and innovations.

EP2
THE FERMI EXHIBITION
AIF - Association for Physics Teaching (Italy)
Local AIF Unit of Pordenone (Italy)
Provincia, Pordenone (Italy)

This exhibition illustrates the great Italian physicist and his work through explanatory documents this time. E Fermi is presented here from the theoretical and experimental point of view. The first approach takes [beta] decay into account and its effects on the existing description of nature, since it introduce the weak interaction as a new force in physics. The second focuses on the discovery of slow neutrons, which eventually led to the liberating of atomic energy - a mile stone in human history.

EP3
THE ACTIVITY of the Local AIF Unit of Udine (Italy)
L. Marcolini, AIF-UD, Research Unit in Physics Education, University of Udine (Italy)

EP4
COMPUTER TOOLS IN TEACHING THE PHYSICAL PHENOMENA
M.S. Al-Kobt, Department of Physics, Faculty of Science,University of Ain Shama (Egypt)
S.A. Hassan, Department of Chemistry, Faculty of Science, University of Ain Shama (Egypt)

Computer tools are now an integral part of contemporary basic and applied science and are approaching a role equal in importance to the traditional experimental and theoretical approaches. The philosophy of this paper expresses well the Chinese proverb: "I hear and I forget. I see and I remember. I do and I understand." We are asking not how the students can be trained to use the computer but how the computer can be used to teach the physical phenomena. Our primary goal is to create an integrated environment presenting more forcefully the physical concepts and of greater intuitive understanding for the students.
The crystal structure of a solid is detemined via the diffraction of waves produced by the periodic arrangement of the atoms. This diffraction is usually measured using X-ray, electron or neutron beams. The use of the reciprocal lattice provides a convenient way of visualising and describing the diffraction pattern of the corresponding real lattice. The diffraction pattern obtained in two dimensions by using an optical diffraction grating resembles in concept the one obtained with the crystal. The diffraction pattern from the grating will be visualised as dots, the size of each being proportional to the observed individual intensity. This produced pattern can be transferred to the computer by means of a camera. All details of analysis worked out on the crystal (i.e. lattice parameters and indexing) can be performed on the pattern recorded in the computer. The present paper describes the experiment as well as the interactive program for teaching this phenomenon which is limited, in our case, to cubic, tetragonal and hexagonal gratings. This can hopefully provide the undergraduate student with an advanced means of understanding.

EP5
LECTURE EX-CATHEDRA, LECTURE EX-VIDEO
C. Agnes, R. Gonnelli, Polytechnic of Torino (Italy)

A Videotape is presented showing a sample of recorded STM (Scanning Tunneling Microscope) experiments, which can be used during the lecture to "see" the individual atoms.

EP6
THE BASIC REACTION OF SOLID STATE PHYSICS
C. Agnes, Polytechnic of Torino (Italy)
F. Herrmann, University of Karlsruhe (Germany)

When electrons in a crystal are considered like the distribution of two Substances, whose established names are n and p, then many phenomena of Solid State Physics may be related to the reaction: n + p

EP7
GAMES, EXPERIMENTS, IDEAS
G. Bosatta, M. Bosia, S. Bosio, G. Candussio, V. Capocchiani, S. Deotto, L Marcolini, M. C. Mazzadi, M. Michelini, G.L. Michelutti, S. Pugliese Jona, L. Santi, C. Sartori, M. L. Scillia, A. Stefanel, Research Unit in Physics Education, University of Udine (Italy)

The exhibition Games, experiments, ideas brings together 90 simple experiments in mechanics, thermology, electricity, electro-magnetism, optics, chemistry, astronomy for schoolchildren of the 11-16 age group. The experiments were realized by CLDF, through the Research Unit in Physics Education in collaboration with with the Associazione per l'Insegnamento della Fisica. The first showing of the exhibition took place in April 1994, on the occasion of the IV Week of Scientific Culture. It was born with 40 experiments prepared by M. Bosia, M. Michelini e M.L. Scillia who were subsequently joined by M.C. Mazzadi and the other members of the group, producing the exhibition on two further occasions in the Museum of Pordenone at the end of '94 and at the beginning of 95 during the V Week of Scientific Culture(April 1995). Moreover on this occasion the exhibition was visited in Udine by about 2200 students and their teachers. They saw the exhibition either on their own or with the help of 15 guides, University professors or secondary school teachers of the Research Unit in Physics Education. The equipment, made from cheap material and easily reproducible,was put on display along with operational illustrations. The exhibition stresses both the playful aspect of individual discovery and the the practical side of things, which are necessary for personal involvement useful for the learning of scientific subjects, especially in the formative phase of students basic knowledge, the period in which the maximum effort is required for the development of scientific culture. The experiments permit the acquisition of fundamental scientific knowledge and the organisation of monothematic educational mini-courses. Without any presumption of completeness, they indicate the correct way of posing questions to oneself and of using knowledge and ability to obtain appropriate answers through appropriate experience. The experience of the previous year, satisfying for the enthusiasm encountered and for the number of visitors to the exhibition whom for the most part requested the help of one of the guides, suggested the organisation of an integrative refresher course for teachers before and during the exhibition. Practical activities on scientific themes were suggested with the aim of rendering the teaching of science more effective in its foundational stage and developing proposals for the school curriculum sensitive to the equipment available for a range of experiments suitable fot the teaching of science to 11-16 year olds.

EP8
ADVANCED CERAMICS MATERIALS
C.N.R.-IRTEC, Faenza, (Italy)

EP9
CORROSION OF SIC BY POLLUTANT OXIDES IN COMBUSTION ENVIROMENT
M.T. Dario, S. Maschio, A. Bacchiorini, DSTC, University of Udine (Italy)

EP10
HELPING UNIVERSITY STUDENTS TO UNDERSTAND PHYSICAL PROPERTIES OF ELECTRONIC DEVICES
W. Barberis, L. Borrelli, G. Casas, C. Ciccarella, J. Cordara, M. Gonzales, G. Goya, G.Heredia, G. Pagnossin, J. Silbermann, L. Simsic, Faculty of Engineering, National University of La Plata (Argentina)
E. L. Peltzer y Blancá, O. M. Cappannini, A. Melgarejo, IFLYSIB (CONICET-UNLP) La Plata (Argentina)

With the contribution of students from previous years in the discussion of goals and new subjects to be included in the curricula, it was possible to make several changes in a solid state physics course for electric and electronic engineering students, trying to get better results in the handling of basic concepts and their application to electric and electronic devices.
The first result obtained was a change in the attitude of the students during both the theoretical and practical parts of the classes. In this work we show the different changes implemented, how they were done in each year since 1992, the teaching problems we tried to solve and an evaluation of the obtained results.

EP11
STUDENT UNDERSTANDING OF THE ENERGY CONCEPT. ITS RELATION WITH CONDENSED MATTER PHYSICS
O. M. Cappannini, E. L. Peltzer y Blancá, A. Melgarejo, IFLYSIB (CONICET-UNLP), La Plata (Argentina)

Our teaching experience in condensed matter courses has shown a poor handling of basic physical concepts such as energy and unclear ideas about models of solid.
Trying to get a wider knowledge about misunderstandings on basic concepts, we have built a survey asking about energy and extended it to subjects such as heat and work which are completely related to the energy concept. It also included a question to identify models of solid.
The test was answered by approximately 150 students belonging to the same level (just after having finished the General Physics courses) and from different universitary careers (electronic engineers, physics and chemistry). The results show similar trends in any of the tested groups.

EP12
WHAT CAN STUDENTS LEARN FROM MEASURING THE BAND GAP OF SEMICONDUCTORS EMPLOYING THE RESISTIVITY VS. TEMPERATURE METHOD?
E. Caselli, University of Centro de la Pcia. de Buenos Aires and CICPBA ( Argentina)
F. Ortega and M. Lester, University of Centro de la Pcia. de Buenos Aires ( Argentina)

This contribution is concerned with the advantages that measurements of the resistivity of a semiconductor vs. temperature offer to acquaint students with fundamental phenomena in solid state physics such as metal-semiconductor contact potential, the influence of impurities on electrical properties and the basic concepts involved in electrical transport.

EP13
A NEW APPROACH TO THE TEACHING OF SEMICONDUCTORS IN THE SECONDARY SCHOOLS OF ALBANIA
R. Corati, Z. Mulaj, University of Tirana (Albania)
K. Corati, "Hasan Prishtina" School, Tirana (Albania)

The core of Physics Curricula for the Secondary schools in Albania was formed many years ago. We already have much experience in teaching mechanics, electricity, optics and also semiconductors.
Our experience in teaching physics in highschool, however, allowed us to recognize the following deficiencies in the teaching of semiconductors.

1. The extremely theoretical character of the introduction of notions is often difficult and monotonous for the students.
2. Demonstrative experiments are not used as a method for stimulating logical thinking of students.
3. The existing curriculum does not bring into the classroom the fast development of technology which is very important to raise the interest of the students.

1. Stimulating the logical thinking of the students on the semiconductor phenomena through experiments.
2. Using figurative and analogue models in order to make the physical principles of the diode and transistor as comprehensible as possible.
3. Putting emphasis on the functional aspects of the diode and transistor through an appropriate selection of electronic schemes.
4. Demonstrating different applications in order to improve the problem-solving capabilities in the semiconductor field.
5. Bringing the technological environment into the classroom.

EP14
RUTHERFORD BACKSCATTERING SPECTROMETRY: A TECHNIQUE WORTH INTRODUCING INTO PEDAGOGY
F. Corni, Department of Physics, University of Modena (Italy)
M. Michelini, G. L. Michelutti, L. Santi, A. Stefanel, Research Unit in Physics Education, University of Udine (Italy)

The Rutherford Backscattering Spectrometry(RBS), which until a few years ago was an important area of research in the physics of solids, is today almost exclusively a routine technique of analysis in the characterisation of samples.It consists in the use of Rutherford's experiment which permits the analysis of the type and the depth-distribution of the elements forming the surface of a sample.
The basics required for its understanding are all contained in the secondary school physics curriculum. Therefore its study is, in one way, a motivational stimulus as regards the topics which are propaedeutic for it and,in another way, a passage to the understanding of the experimental bases of the physics of solids.
The work contains suggestions on two levels. One level deals with the preparation of a collection of educational material on techniques of analysis and the characterisation of properties. The other level contains the more specific suggestion based on the analysis of experimental data, which allows a gradual approach to the theme.

EP15
THE CONCEPT OF THE CROSS SECTION
F. Corni, Department of Physics, University of Modena (Italy)
M. Michelini, L. Santi, F. Soramel, A. Stefanel, Research Unit in Physics Education, University of Udine (Italy)

In basic physics courses the concept of the cross section is often introduced as a semi-quantitative definition, mostly on a geometric basis, as required or after the study of impact in mechanics. It is rarely studied in detail and its significance as a parameter of measurement in many areas of physics (from the field of solids from the point of view of analysis techniques to the nuclear field of high and low energy) is rarely stressed. A cultural analysis for teacher training which may produce the necessary knowledge for a pedagogic follow-up suitable to the role that such a parameter plays in all experimental research is proposed. A pedagogic discussion is contextually proposed.

EP16
A PROBLEM FOR EDUCATIONAL RESEARCH: THE UPDATING OF THE CURRICULUM
F Corni, E. Mazzega, G Ottaviani, Department of Physics, University of Modena (Italy)
M. Michelini, G. L. Michelutti, L. Santi, Department of Physics, University of Udine (Italy)

The curriculum updatin is a problem of:curricular research in the specification of contents conceptual changes research in the sense of characterising of strategies tools and methods to achieve new educational objects.
The aim of the researches in physics education carried out in the units of Modena and Udine in the last 4 years is the building of formal tough by means of experimental situations. The elements pointed out are:

• planning and implementing hardware and software prototypes to execute computer on-line experiments and modelling activities
• connection between physics and mathematics and the role of the two discipline in scientific education at lyceum: didactic proposals
• design ofcomputer on-line experiments, conceptually valuable and suited to simulate thinking on the phenomenon interpretation
• basic ideas for the introduction of quantum physics relevant in the technological development.

EP17
LEARNING TO OBSERVE: A SPECTROSCOPIC ANALYSIS OF OPTICAL FILTERS TO OBSERVE A SOLAR ECLIPSE - THE CASE OF THE TOTAL SOLAR ECLIPSE IN BRAZIL / 1994
M. C. Danhoni Neves, J. R. D. Pereira, F. C. Cardoso, Deprtment of Physics, University of Estadual de Maringá (Brazil)

This work presents a spectroscopic analysis in the ultraviolet and infrared regions of three kinds of optical filters recommended to observe the sun, or, more specifically, to observe total (or partial) eclipses of the sun (which occurred on ll/03/1994, in the southern region of Brazil). Three filters were studied: film ISO 4850, X-ray plate and X-ray plate plus common window glass (transparent). The results showed that the last one was a good filter, even better than the one officially recommended, e.g., ISO 4850. The "Mylar" filter was not studied because it is very difficult to be found in Brazil. The results were used to divulgate, in schools, the recommendations and preventions to protect the eyes during the occurrence of the phenomenon. Our target population were teachers-in-service and students of primary and secondary schools. The interaction of solar radiation with matter was also discussed with University students.

EP18
VIBRATIONAL PROPERTIES OF DIATOMIC LINEAR CHAINS INVESTIGATION USING MATHEMATICA
A. Franchini, Department of Physics,University of Modena (Italy)

I review the vibrational properties of a diatomic linear chain studying several different systems:

• homogeneous diatomic chain
• chain with an isotopic substitution of a light or a heavy mass in a light site
• chain with an isotopic substitution of a light or a heavy mass in a heavy site
• chain with a vacancy
• chain with a force field local modification
• effects of anharmonicity.

EP19
NEW TECHNOLOGIES FOR LEARNING IN THE LAB: A HOME-MADE COMPUTER ON-LINE SYSTEM FOR OPTICAL PHYSICS MEASUREMENTS
A. Frisina, M. Michelini, Research Unit in Physics Education, University of Udine (Italy)

A simple system of acquisition of on-line data has been produced in MS-DOS for the measurement of light intensity versus the position on a segment. It is an up-to-date version in a new operative environment of a system (FENTE) already produced as a prototype for the teaching of physics. A series of measurements obtained by illuminating with a laser from one to five different slits is presented together with the system. Such measurements support a teaching guideline in the field of physical optics.

EP20
THE LINEAR SUPERPOSITION PRINCIPLE AND NON CLASSICAL FEATURES OF MICROPHENOMENA
G. Ghirardi, Department of Physics, University of Trieste (Italy)
R. Grassi, M. Michelini, Research Unit in Physics Education, University of Udine (Italy)

It is by now a widely held view, not only in the circles of educational research, that it is necessary to introduce elments of quantum physics into secondary school teaching. The new Italian programmes (Brocca) also refer to it, and some publishing houses have begun to publish textbooks that are supplemented with a section on quantum physics. Moreover the themes concerned with the physics of condensed matter cannot be faced in a serious way without having at least some idea of how the microscopic world is viewed by quantum physics.
The introduction of such a vision of the world at the secondary school level requires exacting pedagogical research in order to find appropriate themes and methods. Setting aside a global analysis (definitely better, but so exacting that it doesn't leave sufficient time for operative suggestions), conceptual problems characterising the quantum vision of the world have been singled out and individual pedagogic suggestions have been elaborated so that they can be put together like pieces of a jigsaw puzzle.
The principle of linear superposition has been singled out as one of the key-pieces of the puzzle. The analysis of states of polarisation of interacting photons with polaroid and birifrangent materials is suggested for its study. Although it is autonomous, it can be carried out in parallel with that, by now well-known, of the diffraction from two slits, by means of iconographic representation that favours the association of ideas in an analogical way. Particular attention is paid to the concept of trajectory and to the meaning of measure.

EP21
FLUCTUATION PHENOMENA ON METAL SURFACES
L. Gladyszewski, A. Wisniewski, Institute of Physics, Maria Curie Sklodowska University, Lublin (Poland)

In this Paper we present some experiments on electrical fluctuations (noises) as follows:

• "white noise" (thermal fluctuations),
• ion current noise in thermal ion desorption with "Lorentzian type" spectra,
• impulsive ion emission of potassium impurities and additionally,
• fluctuations of solar radio emission at 220 MHz using a radiointerferometer.

EP22
TRANSMISSION OF INFORMATION IN CONDENSED MATTER
M. Glowacki, Pedagogical University of Czestochowa (Poland)

In the paper, the short review of the theory of information and data transmission technique in the optical frequency band is given. The most promising - PCM transmission system on the fiberscopes is described in more detail. The optical frequency band gives the maximal number of transmission channels in the information connection. The fiberscope gives the minimal number of losses of information. This kind of transmission of information can be used in a cable television, videophones and computer terminal.

EP23
DIELECTRIC ANOMALIES IN THE PARAELECTRIC PHASE OF PbZr0₃ NICKEL-DOPED
M. Hafid, H. Elqadim, Department of Physics, L.P.M.C. University of Kenitra (Morocco)
T. Fukami, Faculty of Engineering, Shinshu University, Nagano-Shi (Japan)

In order to make clear the effect of acceptor doping in perovskite compounds, dielectric properties of Ni-doped PbZrO₃ ceramics have been studied with the aid of the thermally simulated current (TSC). The dielectric measurements performed as a function of temperature up to 600deg.C show evident peak of the dielectric costant around 350deg.C depending on an applied frequency. The activation energy calculated from plotting the logarithm of the frequency versus reciprocals of the temperature of loss tangent maxima is about 1,37 eV.
In our studies we try to explain the characteristic temperature dependence of the dielectric constants on the basis of a localized dipole model. That is, the dielectric phenomena are mostly dominated by complex defect dipoles NiZr-VO surrounding each grain surface.

EP24
YBCO-SUPERCONDUCTORS-NEW TOPIC IN TEACHING "PHYSICS OF SUPERCONDUCTORS"
A.Harabor, M.Ursache, M.Socaciu, Department of Condensed Matter Physics, University of Craiova (Romania)

Our teaching experience revealed that the very rich information concerning preparation and characterisation, crystal structure, transport properties, magnetisation and susceptibility measurements, critical currents, Hall effect, some theoretical models and the impact of YBCO superconductors on technological applications could be organised in an original form. In our contribution we present the theoretical details about this topic as well as the adequate experiments.

EP25
THE SEMICONDUCTOR DIODE AS: A RECTIFIER, A LIGHT SOURCE, A LIGHT SENSOR, A PHOTOVOLTAIC CELL
F. Herrmann, University of Karlsruhe (Germany)

EP26
WHICH SUBSTANCES GLOW?
F. Herrmann, University of Karlsruhe (Germany)

EP27
THE A.I.F. ACTIVITIES
M.C.Maccario Mazzadi, Executive Committee of AIF, (Italy)

The Association for Physics Teaching is a non profit organization operating with the aim of improving physis education and to better the standard of scientific culture in Italy.
To achieve such aims the A.I.F. carries out any suitable activity and, in particular, prints and disseminates publications on cultural and educational subjects and organizes meetings, conferences and training activities for teachers.
49 units have been set up in different places of Italy which operate locally by organizing teachers training courses, seminars, exhibitions, etc. An AIF Unit constitutes a reference point for physics teachers living in its area of activity.

EP28
CREATION AND DETECTION OF "THERMAL" WAVES THROUGH ABSORPTION OF MODULATED LIGHT BY SOLIDS
F. J. Macedo, J. A. Ferreira, Department of Physics, Minho University, Braga, (Portugal)

Light absorption by non transparent materials induces periodic heating of the samples, which can be measured by several methods, detecting phenomena induced by the thermal waves produced (acoustic waves, infrared emission, beam deflection (mirage effect), etc).
The thermal properties of the materials can be measured by any of these methods, taking into account the frequency dependence of the amplitude and phase of the signal.
These effects can be qualitatively illustrated by simple experiments which can be performed using common materials and a stroboscopic source.

EP29
TEACHlNG SOLID STATE PHYSICS ON A REGIONAL SCALE: A PATAGONlAN EXPERIENCE
E.N. Martinez, Balseiro-U N. Cuyo Institute, Atomic Centre of Bariloche (Argentina)

For the last 15 years, the Instituto Balseiro, located in Bariloche, in the argentinian Patagonia, has been organizing courses on Solid State Physics at the undergraduate and graduate levels. These courses are attended by participants from all Argentina and lately, with the support of ICTP, from Latin America.
This type of regional courses lead to a rational use of the scarce resources available in the area, and encouraged horizontal collaboration.
The organizational problems (both pedagogical and bureaucratic) will be discussed, advantages will be stressed, and errors and pitfalls will be marked.

EP30
OPTICAL SOLITONS AS RELATIVISTIC MIRRORS
M. J. Martins, Center for Electrodynamics Technical University, Lisboa (Portugal)

Optical solitons represent the envelope of a light wave that establishes itself as a stable solution in a non-linear dispersive medium. The nonlinearity is due to the Kerr effect which causes the medium properties to be dependent on the square power of the electric field of the light wave
n(I) = nL + n₂I
where I is the light intensity which is proportional to the square of the electric field.
Due to the Kerr effect there is a self induced pulse broadening which is compensated by the group dispersion, in the anomalous dispersion zone where
v g / >>0
so, the higher frequency components have a group velocity which exceeds that of the lower frequencies which causes a blue shift at the pulse front and a red shift at the wake. The self induced phase modulation due to the Kerr effect has the opposite effect, and so a non-linear dispersive solution is obtained which behaves as a linear non dispersive one, preserving its form in a quasi particle manner. This solution which can be derived from the non-linear Schroedinger equation, by using the inverse scattering method is the soliton
u) = sec h(_p)
The propagation of a soliton through a medium creates a non-stationary disturbance of the medium refractive index which propagates with velocity =v/c, close to unity.
The interaction of a wave of small intensity with the soliton originates a reflection which causes a double Doppler shift of the wave frequency, that can attain very high values.
^! = (1+n) / (1-n)
Under resonance conditions very high values of the reflection coefficient can be obtained leading to an almost "mirror" reflection.

EP31
ZERO DIMENSION TECHNOLOGY AND PHYSICS EDUCATION
A. Masi, M. Adelaide Institute, Aosta, University of Torino (Italy)

The poster deals with the main difficulties still existing in the construction of the quantum dots: our aim is to illustrate the extraordinary importance of the present and future zero dimension technology applications in our daily life, also showing the possible influence and interaction of high progress with physics teaching at different levels.

EP32
TINY MOLECULES - A STUDY OF THE PROCESS OF LEARNING
H. Mayr, Institute for Theoretical Physics, University of Vienna (Austria)

On 1994-10-14 a class of 34, 15 year students of a "Realgymnasium" in Vienna/Austria, worked hard to get some insight into the "diameter" of molecules.
First they got some pieces of information from their teacher. "If a drop of rinsing liquid touches the surface of the water, the liquid spreads over the surface and builds a layer whose thickness is in the same order as the diameter of molecules". Then they got the assignment to develop a method to estimate the order of the diameter of the molecules roughly, using a flat vessel, some water, some baby powder, a syringe, some rinsing liquid and a ruler.
The poster describes the way they worked, typical problems they had to solve and the value they got.
A short sketch of the pedagogical and didactical path of this lesson is enclosed.

EP33
SIMPLE ON-LINE MEASUREMENTS IN THE SCHOOL: A DIDACTICAL EXPERIENCE
L. Marcolini, AIF-UD, Research Unit in Physics Education, University of Udine (Italy)

We discuss action-research experiments carried out with technical secondary school students 16-18 which consist in the planning, production and implementation of prototypes of on-line measurement system of different physical quantities (time intervals, temperatures, light intensity, etc.) by means of sensors. It began at a teacher training seminar at a national level which dealt with the use of the computer for physical measurement in the didactical laboratory. The importance of the experiments consists not only in the individuation of methods of active work and planning techniques in a traditional teaching context, but even in the transversal nature of the goals. The experiments were viewed as an opportunity for practical activity as part of a technological course(Technological Management Course/SISTEMI), and were based on the obtainment of scientific knowledge useful for working on the analysis of physical properties, as well as technological management. The prototypes produced were chosen with a view to the production of simple instruments and modern technology for the physics laboratory.

EP34
TERMOGRAFO: A COMPUTER ON-LINE ACQUISITION SYSTEM FOR TEMPERATURE MEASUREMENTS IN PHYSICS EDUCATION
E. Mazzega, Department of Physics, University of Modena (Italy)
M. Michelini, Research Unit in Physics Education, University of Udine (Italy)

We describe a temperature data acquisition system for the educational laboratory. Real-time plotting of the outputs of up to 4 sensors allows to easily perform traditional and non-traditional experiments, for example on no-equilibrium states. We suggest a few experiments and discuss the educational uses of the system.

EP35
THERMAL CONDUCTION IN SOLIDS: AN ON-LINE EXPERIMENT FOR SECONDARY SCHOOL AND UNDERGRADUATE STUDENTS
E. Mazzega, Department of Physics, University of Modena (Italy)
M. Michelini, Research Unit in Physics Education, University of Udine (Italy)

The study of heat conduction in solids is a topic which is often neglected either because there aren't simple quantitative experiments available, or because the laws that regulate the phenomenon are considered difficult.
Yet, it has a non negligible importance in many areas of daily life in which we find ourselves facing problems connected with the transfer of energy in the form of heat.
Measurements of the temperature's course across time in four equidistant points on a metallic bar in different conditions can be carried out by means of a simple on-line data acquisition system (Termografo).
The finite differences analysis of the temporal evolution of the temperatures allows a discussion of the transitory and the subsequent steady state; it emphasizes the role of thermal properties of the material studied and it also simplifies the calculation of the thermal conductivity.

EP36
ELECTRICAL CONDUCTION IN METALS: A DIDACTICAL EXPERIMENTAL STUDY
M. Michelini, Research Unit in Physics Education, University of Udine (Italy)
A Sconza, G Torzo, Department of Physics, Padova University (Italy)

Hall voltage measurements as a function of the injected current and of the magnetic field were carried out for two different metallic samples of copper and zinc respectively. The measures obtained both with a simple commercial computer on-line system for educational laboratory and with an home made apparatus are proposed as examle of experimental study of the electrical transport properties in metals.

EP37
ELECTRON TRANSPORT STUDIES OF AMORPHOUS AND NANOCRYSTALLINE ALLOYS: ELECTRICAL RESISTIVITY AS A PROBE OF PHASE TRANSITION
K. Pekala, Institute of Physics, Warsaw University of Technology (Poland)

The electrical resistivity is a diagnostic tool to study the structural and magnetic evolution of amorphous alloys with accuracy higher than X-ray method. It allows to determine kinetics of crystallization including crystallization temperatures, activation energy and Avrami exponents. Moreover, electron scattering on grain boundaries in nanocrystalline alloys may be analysed using the Mayadas - Shatzkes model.

EP38
TRANSPORT STUDIES OF NEW SUPERCONDUCTING MATERIALS
M. Pekala, Department of Chemistry, University of Warsaw (Poland)
M. Ausloos, SUPRAS, Institute of Physics, University of Liege (Belgium)

The precise electric charge and heat transport studies performed in the normal, superconducting and mixed states of high critical temperature superconductors supply an important characterization, complementary to the data obtained from non-transport techniques. They include the traditional electrical resistivity, thermoelectric power and thermal conductivity measurements, which probe charge and heat currents caused by the electric and temperature gradients, respectively. When the magnetic field is additionally superimposed on the superconducting sample at orientation perpendicular to the electric or temperature gradients, the new phenomena like excess electrical resistivity, excess thermoelectric power, Nernst effect and magneto-thermoconductivity may be registered. They supply the unique information on kinetics of vortices (magnetic flux lines) present in the mixed state of the type ll superconductors. The percolation line (analogical to irreversibility line) and other quantities like transport entropy, critical magnetic field H, Ginzburg - Landau parameter, coherence length, mean activation energy of the thermally activated processes and the thermal Hall angle describing the vortex motion may be derived from the experimental data. The above listed quantities give the average parameters for the polycrystalline superconductors. On the other hand, the anisotropy of these parameters involved by the layered structure of high temperature superconductors, may be exactly determined for the single crystals, textured and oriented thin film superconductors. The transport studies provide with the experimental data needed for testing the superconductivity models. Moreover, they enable to perform quick and accurate characterization of superconductors necessary for optimization of the production and treatment technological processes.

EP39
TEACHING MICROSCOPIC BEHAVIOUR OF MATTER ON A DETAILED BASIS WHEN LECTURING ABOUT CONDENSED MATTER
C. A. Raffo, M. A. Rebollo, Faculty of Engineering, University of Buenos Aires (Argentina)

This work tries to show the need of a thorough microscopic discussion, when teaching the physics of condensed matter, from the simplest to the more complex topics. Normally we are faced with the choice between describing and teaching the phenomenological aspects as derived from experiment using only an extensive description on the basis of outer magnitudes (field and thermodynamics functions for example), or to follow a detailed description sustained on the predictable behaviour of the particles that basically constitute matter at low energies. This last case does not necessarily replace the former, but has the advantage that we appeal constantly to simple laws of interaction between particles and to statistical concepts.
We sustain that the choice is not a sharp one but, when lecturing a course nowadays, the microscopical description is needed always as a basis for enhanced student creativity in research and to foresee new technical ideas.
The work refers two examples of how to deal with teaching in this way: the case of water condensation in the atmosphere and the less known photon-drag effect in semiconductors.

EP40
STUDENTS' INVESTIGATION OF TRIBOELECTRICITY
T. Ryu, Y. Hara, Sophia University (Japan)

A simple experiment of triboelectricity has been developed for high school student's investigation in Japan. One kind of small particles of sugar glass and styrofoam are poured at the top of an inclined plate covered by a sheet of one kind of material: rubber, polyethylene, chloroethylene etc. They slide down on the plate and into a Faraday pail. A student uses a surface voltmeter to measure voltage of the surface of the Faraday pail and calculates electric charge of the particles. He can investigate practically which factors affected the charging and discharging process of particles by control of many factors. We referred to papers of Dr N. Wilson and Mr Ian Pavey distributed in the IOP workshop of the l994 ASE meeting.

EP41
CONDENSED MATTER PHYSICS TEACHING AS AN INTERFACE BETWEEN MATERIALS PREPARATION AND STRUCTURE ANALYSIS IN A PHYSICAL ENGINEERING DEGREE
L. Santos, T. Monteiro, Department of Physics,University of Aveiro (Portugal)

In the Physical Engineering curriculum at the University of Aveiro, the students' in the 4th year have to deal, simultaneously, with two disciplines they like particularly: Materials Preparation and Structure Analysis of Solids.
In fact we can say that these two disciplines fulfill the main objectives of the materials area in this degree.
The 4th year is a very special one for the students. On one hand they are eager to work in subjects they've heard of, namely on the preparation of the new materials they know from the literature, and yet they are aware that they do not have all the theoretical tools to understand the physical processes involved in that preparation. On the other hand, nor do they know the theoretical and practical means to analyse the structure of the materials they want to prepare.
From where we stand, as teachers, we must give them the theoretical background necessary to understand the physical processes involved, and want to keep them interested in accepting the theoretical preparation in order to apply it with good practical results, in both preparing and analysing new materials and their structure.
The main difficulty here is that the theoretical background, the process of preparation and the structure analysis have to be carried out during the same semester.
The present work refers to both students' and teachers' goals and how they were dealt, concluding with the presentation of the final results the students' achieved, and the way in which these two disciplines made the difference in their way of facing the fundamental and applied research in Condensed Matter Physics.

EP42
VISUALIZATION OF X-RAY MEASUREMENTS ON COMPLICATED STRUCTURES
V. Sirenko, B. Verkin Institute for Low Temperture Physics and Engineering, Kharkov (Ukraine)
A. Sirenko, V. Bruck, Kharkov State University, Ukraine

Advanced materials, like the high temperature superconductors, are often characterized by the complicated crystallographic structures, puzzling for imagination and identification by methods of structural analysis. Thus, education of modern specialists in relevant fields requires efforts at earliest stages of training with continuous absorption of the students into updated computational and technical means of investigation. We propose such a scheme for a teaching course of X-ray investigation in succession: secondary education, university, post graduate training. It includes a preliminary acquaintance with basic principles of the description of the periodic medium and its interaction with incident radiation, followed by information on groups of symmetry, natural examples and corresponding X-ray patterns. A special PC software provides object lessons - display of the unit cells, corresponding to a set of lattice parameters, derived from X-ray measurements after different heat treatments of the starting materials.

EP43
TEACHING LIQUID CRYSTALS: CURRICULA AND LABORATORY EXPERIMENTS
M. Socaciu, M. Ursache, A. Harabor,, Department of Condensed Matter Physic, University of Craiova (Romania)

This paper presents the implications of the science of Liquid Crystals for teaching, based on direct experiences and quantitative measurements. The curriculum of the "Liquid Crystals" course contains the following chapters: molecular structure and classification of the liquid crystals; theoretical models for the liquid crystals; defects and textures of the liquid crystals; physical properties of the liquid crystals; thermo-optical and electro-optical effects; applications of the liquid crystals.

EP44
NEW MATERIALS AND THE GENERATION GAP
M. Staszel, University of Warsaw (Poland)

For the questioned teacher trainees just over twenty, "new materials" have been around for a big part of their lives. Poor connection is seen, however, between their physical properties and applications. Our schools give no help, as they teach of 19th century materials, so this opportunity of showing relevance of physics is lost.

EP45
INTRODUTION OF QUANTUM PHYSICS INTO THE SECONDARY SCHOOL CURRICULUM
A. Stefanel, Scientific Liceo "Marinelli", Udine (Italy)

This work prevides an illustration of the introdution of quantum physics into the secondary school curriculum. Electrical transport properties in solids is taken as an example of the application of some of the concepts involved in the theory. We present the general educational context, the general objectives, and the themes discussed. Lastly, we evaluate the results obtained.

EP46
BOMBARDMENT INDUCED LIGHT EMISSION - NEW METHOD FOR SURFACE DIAGNOSTICS
M. Suchanska, Institute of Physics, Pedagogical University of Kielce (Poland)

There are some different secondary processes induced by ion bombardment of solids which can be used for surface diagnostics. One of the most interesting phenomena is light emission observed under the surface, termed ion - induced photon emission (IIPE). The IIPE spectra provide information about the mechanism of interaction of ion beams with materials and about the processes occurring on the surface under ion bombardment. Therefore, the bombardment induced light emission spectroscopy is a good method for the identification of particles sputtered from the surface and can be used for sensitive surface diagnostics [1]. On the other hand the bombardment of semiconductor and dielectric targets is accompanied by the optical radiation which comes from the surface, called ionluminescence (IL) [2]. In this case the IL spectra can give information about the mechanism of the formation of radiation defects in the bulk. Our intention is not only to demonstrate the possibilities of practical applications of the IIPE and IL methods but also to pay attention to didactical aspects of experimental results in teaching about the science of condensed matter. It seems that knowledge of the problems connected with interactions of ion beams with materials should facilitate an understanding of transformation between a macroscopic description of surface phenomena and their microscopic interpretation.
References:
[1] M.Suchanska, Induced Photon Emission of Materials and Possibilities of Its Application for Surface Diagnostics, in NATO ASI Series vol.283,p. 175-181, ed. Kluwer Acad. Publ, Dordrecht, Boston, London, 1995
[2] M.Suchanska, A.I.Bazhin, E.I.Konopelko, Ion Beam Induced Luminescence of Alkali Halide Crystals. Phys.stat.sol. (b) 182 (1994) 231

EP47
SOME ASPECTS OF TEACHING SOLID STATE PHYSICS AT PEDAGOGICAL UNIVERSITY IN KIELCE
M. Suchanska, M.Wysocka-Kunisz, Institute of Physics, Pedagogical University of Kielce (Poland)

Most programs on solid state physics in Polish universities are based upon the well-known monograph "Introduction to Solid State Physics" by Kittel [1]. Such program consistent of lectures and exercises is also realized at Pedagogical University in Kielce at the teacher specialization. In our opinion, for more profound understanding of the basic problems in solid state physics, it may be useful to complete standard teaching methods by using the seminar method [2]. Such approach facilitates getting knowledge of problems like experimental methods in solid state diagnostics or new material science. Advantages and disadvantages of the proposed method are discussed.
References:
[1] C.Kittel, Introduction to Solid State Physics, Warsaw, ed.PWN, 1978
[2] R.I. Arends, Learning to Teach, Warsaw, ed.PWN, 1994

EP48
A NEW EXPLANATION OF THE PROCESS OF ACCELERATING ELECTRONS AND CONNECTED PHENOMENA
K.Turzyniecki, Department of Physics, Technological University of Warsaw (Poland)

The effect of the mass of electron increasing with its velocity discovered by Kaufmann in 1901, was described by Abraham, Lorentz, Einstein and Lewis in their indipendent theories. The formula which they derived after many carefully performed experiments, shows the dependence of the mass of the electron on its velocity. However, the ways of arriving at this formula leave room for seriou2s doubt. None of the hitherto theories took into consideration the processes of the interaction which cause the effect. Also, the theories did not notice the other phenomena which are integrally connected with the acceleration of electrons in the electric field, but are important for us if we are to understand the totality of the process.
The new approach to the acceleration of electrons, presented in the paper, not only explains the mechanism of the increase in mass and kinetic energy of the accelerated electrons, but also points to other accompanying phenomena, making it possible to understand them better. In the light of the new approach to the Kaufmann effect the meaning of the concepts of mass and energy becomes clearer.

EP49
ON THE ANALYSING OF INTERNAL CRYSTAL FIELDS MATTER
B. N. Umurzakov, Institute of Nuclear Physics, Alma ata (Kazakhstan)

On the basis of calculation of crystal fields induced splitting of excited atomic levels for different cases in solids the methods for defining of crystal electric, magnetic and stress fields parameters are offered. In consideration of two (three) photon resonance ionization with using ultrashort laser pulses it is necessary to define such parameters without changing crystal fields. The pulse duration t of resonance excitement of atoms depends on the material.
In particular, in order to exclude temperature induced changes of crystal fields in noble metals t must be sufficiently short in comparison with electron-electron collisions relaxation time [1].
It is known that electric field gradients (EFG) in atom sites of crystals with cubic symmetry are equal to zero and they appear while arising the distortion of symmetry. Due to interaction of quadrupole moment with EFG electron levels of probe atoms split. Impurities with small atomic radius or host atoms (in some special cases) may be used as probe atoms. Thus from quadrupole splittings of spectral lines one can obtain EFG values. The possibility of defining elastic stress tensor components _ik follows from a connection with EFG-tensor {_ik} [2]

_ik= (1+) ° C_ikjm °_jm

EP50
LIGHT RAY PATHS THROUGH INHOMOGENOUS MEDIA AS OPTICAL FIBERS
M. Ursache, M. Socaciu, A. Harabor, Department of Condensed Matter Physics, Faculty of Sciences, University of Craiova (Romania)

The graphical representation of the light ray paths for different refractive index profiles as one dimensional structure, cylindrical distribution correspondent to the fibers with a step-index profile or a spherical distribution is presented. Also different initial conditions as different starting points are taken into account in the study of the light ray propagation through inhomogenous media.

EP51
INFLUENCE OF A STRONGLY DIVERGENT ELECTRIC FIELD ON THE CONVECTION IN WEAKLY CONDUCTING LIQUIDS
H.W. Vanderschueren, C. Beck, M. Biron, A. Vanderschueren,University of Liege (Belgium)
V. Jacquet, University and Schumann Institute, Eupen (Belgium)
M. O. Louppe,D.I.C. Coll. et Coll. St. Benoit-St. Servais, Liège (Belgium)
R. Goffaux,Centrale électrique de Vianden, Vianden (Luxembourg)
R. Coelho,Ret. from CNRS, Vaucresson (France)

In 1931, H. Senftleben discovered that an electric field enhances the heat transfer from a wire heated in a gas. Some time later he extended his study to dielectric liquids. From this time, numerous studies have been made with the same configuration he used himself, namely a thin wire in the axis of a cylinder. We have proposed a doubly divergent configuration (a wire in the axis of a torus) which proved to be more convenient to illustrate some peculiar features of this phenomenon: the "transparency" of this configuration allows very convincing optical observations (by Schlieren optics) in conjunction with electrical measurements. Moreover we can propose the laplacian solution of the system.
Beside some known properties, such as ionic or dipolar impurity effects in poorly conducting liquids, we propose to emphasize here two effects never reported before us: the existence (and visualisation) of a stable frontier between cold and warm liquid maintained by electrical repulsion and existence of relaxation discontinuities in the conduction current.

EP52
TEACHING FERROFLUID ON INTRODUCTION PHYSICS
G. Xuan, Department of Physics, East China Normal University, Shanghai (China)

A demonstration experiment on magnetic properties of ferrofluids is described and commented which is in use as introduction to different parts of nano materials.

EP53
ELECTRON TRANSMISSION THROUGH EVERYDAY AND NEW MATERIALS: A STUDENT EXPERIMENT
M. Gambaccini, G. Zini, Department of Physics, University of Ferrara (Italy)
M. Pamini, c/o Department of Physics, University of Ferrara (Italy)

We propose a student experiment on electron transmission through new and everyday materials. The electrons are emitted by a ⁹⁰Sr radioactive source, and detected by a Geiger-Muller counter. The ionization events are recorded on Macintosh memory by means of a MBL acquisition system. The goal of the experiment is that of determining the transmission curve as a function of the material width, of discriminating the contributions to the total transmission curve by component curves, of estimating the electron ranges in the materials used and in those surrounding the experimental apparatus.