1. High School Students Face Superconductivity Lorenzo Santi Research Unit in Physics Education Department of Chemistty, Physics and Environment University of Udine (Italy) lorenzo.santi@uniud.it

2. The Physics Education Research Unit at the Udine University Permanent Staff Marisa Michelini (full professor) Lorenzo Santi (associate professor) Alberto Stefanel (researcher) PhD Students Stefano Vercellati Giuseppe Fera Emanuele Pugliese Associate Visiting Teachers Alessandra Mossenta Giacomo Bozzo Department of Chemistry, Physics and Environment Interdepartmental Centre for Research in Education Via delle Scienze 206, Udine, 33100, Italy

3. Students’ low interest in science ( PISA results  PISA 2006 - Science Competencies for Tomorrow's World )  An improvement of the scientific teaching is needed  revision of the curricula  enhance the scientific teaching and the teacher formation – Re-organize classical physics introducing elements of modern physics – Build bridges between MP and CP – Build bridges between science and technology – Adopting active teaching/learning (T/L) strategies – Promote the use of hands/minds-on WHY SUPERCONDUCTIVY 3

4. Introduction of SC and EM with hands/minds-on, measurements carried out by sensors, modeling, simulations, … MOSEM and MOSEM 2 Projects (Supercomet family projects: http://mosem.eu)http://mosem.eu HOW (we are doing it) 4

5. European Projects MOSEM e MOSEM 2 Minds-On experimental equipment kits in Superconductivity and ElectroMagnetism for the continuing vocational training of upper secondary school physics teachers http://supercomet.no/ MOdelling and data acquisition for the continuing vocational training of upper secondary school physics teachers in pupil-active learning of Superconductivity and ElectroMagnetism based on Minds-On Simple ExperiMents LIFELONG LEARNING PROGRAMME Leonardo da Vinci 5

6. Introduction of SC and EM in upper secondary school, with hands/minds-on, integration of measurements carried out by sensors, modeling, simulations, video analysis MOSEM and MOSEM 2 Projects (Supercomet family projects: http://mosem.eu) URDF-UNIUD USB R-T & Hall on-line acquisition and modeling Teacher Training and Students Learning  T/L paths from E.M. to SC  Active learning (strategies IBL, Problem Solving, RTL)  Tutorials based on active, inquiry based approaches and that can promote it. HOW

7. In the final version of the project, Mosem 2, we proposed a model of teacher training and educational experimentation based on a path on Electromagnetism and superconductivity, using more than 100 simple and 8 high tech experimental apparatuses. 7

8. All this is inserted in a path of work in classroom, with computer modeling activies and measurement with online sensor data acquisition or demonstrative experiments. 8

9. 9 The educational tools LOW TECH KIT Magnetic interactions, E.M. induction, Eddy currents

10. HIGH TECH KIT Fig. 4.1.2A Experimental set-up components. 10 The educational tools Critical Temperature of YBCO

11. YBCO. Temperature Sensor Heater HIGH TECH KIT 11 The educational tools Temperature dependence of resistance

12. HIGH TECH KIT 12 The educational tools Hall Effect

13. HIGH TECH KIT Persistent currents Levitation pinning The MAGLEV train Para-Ferromagnetic transistion (gandolynium) The educational tools

14. The educational path Magnetic properties of superconductor -Interaction between magnets (exploration and discussion by means of field lines rappresentation) -Meissner effect -E.M. induction and eddy currents -The pinning effect Resistivity vs temperature -Temperature dependence of resistivity for metals and semiconductors -The Hall effect -Critical temperature for a superconductor

15. Research experimentations: (since 2006) Laboratory activities in school (national plan for scientific orientation) Summer schools for upper secondary school students Preservice and in service teacher training experimentations In the last two years: 8 contexts (UD-PN-CS-BA-KR -SI: 295 students ) Explorative activities (informal learning): 4 contexts (UD-PN-Frascati- 685 students)

16. Which topics in superconductivity can be introduced by means of the phenomenology? How students face the main conceptual knots?

17. A full example: Exploring the phenomenology of the Meissner effect Aim : to understand correctly the effect in the framework of the magnetic interaction between objects. Tools needed: A disc of YBCO (YBa 2 Cu 3 O 7 ), Tc ~ 90 A bath of LN A (few) magnet (A compass) (A B field probe)

18. Preliminar exploration with compasses or magnets  The YBCO, at room temperature, does not interact with any magnet When the YBCO is brought to thermal equilibrium in a bath of LN(77K) … … it interacts with magnets  levitation At lower temperature

19. Have the properties of the magnet changed? Have the properties of the YBCO disk changed? How? How can we interpret the changes? Questions

20. Are the properties of the magnet changed?  Wherever the magnet is at T e or at T NL, its interactions with other objects (not YBCO) are qualitatively (and essentially quantitatively also) unchanged.  The B field measured around a magnet with a B probe, has the same intensity (and direction) Are the properties of the YBCO disk changed? – Before the YBCO disk doesn’t interact with the magnet – Then the YBCO interact strongly with the magnet  Yes, (Only) the magnetic property of the YBCO are changed In which way?  Hypotesis

21. The YBCO becomes a ferromagnetic object?  If the magnet is reversed (180° rotation), levitation occurs in the same way: it is always a repulsive effect ! When a magnet interact with a ferromagnetic object there is an attractive effect NSNS SNSN No: the YBCO disk does not become ferromagnetic

22. The YBCO becomes a magnet and it interacts with another magnet as they are facing with the same polarity? Magnetic Suspention Magnetic levitation of a magnet on a SC MAGNET SUPERCONDUCTOR MAGNET constrained free

23. No: the YBCO disk does not become a magnet ! Two magnets repeal each other only when they are constrained to face with the same polarity  rotation and attraction But the magnet is free and it is repelled

24. The YBCO disk at T=T NL, evidence the property to repeal the magnet in any case ?  Yes, the YBCO evidence the property to repeal in any case a magnet – If we move gentle the magnet, it oscillate around a local equilibrium position – If we use a magnetic cube it will rotate till its magnetic axe becomes approximately horizontal – -When we put a magnet close to the side of the YBCO disk a repulsive effect it occurs in any case If the magnet is reversed, levitation occurs in the same way: in any case a repulsive effect will happen.

25. The YBCO disk at T= T NL “acts” magnetically without the magnet close to it? For instance, can we expect an interaction between an iron clip and the YBCO disc?  The YBCO does not “act magnetically” without a magnet close to it - An experimental test will be in any case dramatically negative: nothing happens in any case

26. What kind of magnetic property we are analyzing? - Exploration of the interaction of a magnet with different types of materials (aluminum, copper, water, wood, graphite) by hanging these and see if they are attracted, repulsed or not affected by the magnet. Diamagnetic materials: they show “magnetic properties” (repulsive) only in presence of the magnet  Pyrolitic graphite levitates too  The YBCO disk at low temperature becomes diamagnetic

27. The diamagnetic phenomena are usually weak. In the case of the SC the diamagnetic effects are very intense. To understand, we have to “see” what happens inside the YBCO. -Does the external field of the magnet penetrate the YBCO? We can test that.

28. If you make a sandwich magnet – YBCO – iron slab - At T=Te you can lift it by pulling the magnet  We know that the magnet has no effect on YBCO at this temperature, so there is an action of the magnet on the iron  The field of the magnet “arrives” on the iron passing through the YBCO  A magnetic field can exists in YBCO at room temperature - At T=T NL this effect usually disappears and you can’t lift YBCO and iron (Note: this is not completly true if there is some pinning effect). -  The field of the magnet can’t “arrive” on the iron and we can conclude is really small or negligibile through the UBCO  The magnetic field inside a YBCO at LN temperatures is negligibile.

29. A. Stefanel, URDF-UNIUDLab SupCond-Pigelleto29 Is the the field zero inside the YBCO or just very weak? -The same magnet leaved over the YBCO at T=T NL levitate at the same height -If we change the magnet the height of levitation changes, but is the same for each magnet -Measurements of B just out side the YBCO  For a defined range of the external B field the YBCO reacts to it  The current increase as the magnet goes closer to the YBCO

30. A students’ outcome example Summer School Pigelleto 8-10 sept 2010 (PLS- Università di Siena  IDIFO3/MOSEM 2 ) Didactic Lab on SC - 3,5 h (MOSEM 2 experiment ed poroposals). 40 students (17 – 18 years old)

31. 4 IBL Worksheets for the learning path. Worksheet 1 – Interaction between magnets (discussion using field lines representations) Worksheet 2 – Meissner effect

32. The ideas of students SC 2 – Interaction between magnetic dipoles C. Draw the field lines, after the transition. Explain the picture 4/40 10/40 4/40 22/40  the field lines do not penetrate the Ybco if T<TNL T amb T NL T amb T NL T amb T NL T amb T NL

33. 15/40 SC produces a field (modell magnet/magnet) 3/40 the lines penetrate SC at T>TNL 3/40 7/40 8/40 T amb T NL T amb T NL T amb T NL C. Draw the field lines, after the transition. Explain the picture SC 2 – Interaction between magnetic dipoles The ideas of students

34. 12/40 «the properties of the YBCO have changed» «the decrease in the temperature produced a change in the behaviour of the YBCO» 14/40 «The disc of YBCO changes its properties. It repels the magnetic field» 5/40 «The YBCO disc is magnetized» 3/40 Re-arrangement of the atoms 6/40 NR B3.1 Have the properties of the magnet canged? B3.2 Have the properties of the YBCO changed? B3.3. What are the properties changed and in which way? SC 2 – Interaction between magnetic dipoles

35. -Use of the line field representation to take into account : -The repulsion (37/40, but one third following the magnet magnet repulsion scheme) -Peculiarity of YBCO (B=0) (25/40 in the rappresentation, 27/40 nin the explanations) -Change of magnetic properties -Features included in the explanations: -Levitation (without constraints) (2/3  3/3) -Null field (2/3) -Process that happens at the decreasing of T and it changes the YBCO properties (40) below a threshold temperature (1/2) Summary of the results for the L path on Meissner effect

36. E.M. Induction and eddy currents 36

37. N S S1S1 N S  S1 (B)<  MAX  S0 (B)   MAX 2 0 1  S2 (B)<  MAX S2 S1 Bo Conceptual tools:  Field lines (operative definition)  The flux of B (  (B))  The FNL law

38. N S S1S1 N S 2 0 1 S2 S1 Bo  S2 (B)/  t = (  S2 (  t) -  S2 (0))/  t= (  S2 (B) -  MAX (B))/  t <0  S1 (B)/  t = =(  S1 (  t) -  S1 (0))/  t= (  MAX (B) -  S1 (B))/  t >0 Conceptual tools:  Field lines (operative definition)  The flux of B (  (B))  The FNL law

39. N S S1S1 N S 2 0 1 S2 S1 BoBo I ind DL -F-F F -F = I ind (  L  B) F = -(-F) Conceptual tools:  Field lines (operative definition)  The flux of B (  (B))  The FNL law Lifting (braking) effect

40. Corrispondence between the “braking” of the magnet in presence of a conductor and the levitation, if the conductor is “perfect” (R=0) and the currents initially induced by the magnet never stop.  Superconductor : a system with B=0 and R=0!

41. Meissner effect vs pinning Train a la MeissnerTrain “pinned”

42. Activity experimented in three summer schools for selected students of all Italy 17-19 aged (Univ. Udine) Udine 2007 (50 students) Udine 2009 (40 Students) Udine 2011 (40 students) Temperature dependence of resistivity

44. Lab SupCond-Pigelleto44 Free cooling in LN Heating step by step

45. 20% of answers: only the final temperature of the transition is recognized

46. 80% of answers: The full transition interval is recognized

47. Conclusions  Activities highly motivating that lead to significant partecipation (and learning)  Even in front of a complex phenomenology (see for example the puzzling difference between the Meissner effect and the pinning), the students are able to acquire the conceptual tools to descrive and analyze the phenomena involved and to develope models that take into account the relevant aspect of the superconductivity.  Strong integration with “traditional” topics in E.M.

48. 48 LOW TECH KIT The educational tools

49. 49 LOW TECH KIT The educational tools

50. 50 LOW TECH KIT The educational tools

51. 51 LOW TECH KIT The educational tools

52. What happens if the magnet is before putted over the YBCO disc and then dipped into the LN? - The magnet levitates  The YBCO disc repeals in any case the magnet

53. A. Stefanel, URDF-UNIUDLab SupCond-Pigelleto53