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High School Students Face Superconductivity

High School Students Face Superconductivity. Lorenzo Santi Research Unit i n Physics Education Department of Chemistty , Physics and Environment University of Udine (Italy) lorenzo.santi@uniud.it. The Physics Education Research Unit at the Udine University. Permanent Staff

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High School Students Face Superconductivity

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  1. High School Students FaceSuperconductivity Lorenzo Santi Research Unit in PhysicsEducation DepartmentofChemistty, Physics and Environment Universityof 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 VercellatiGiuseppe FeraEmanuele Pugliese Associate Visiting Teachers Alessandra MossentaGiacomo Bozzo DepartmentofChemistry, Physics and Environment InterdepartmentalCentreforResearch in Education Via delle Scienze 206, Udine, 33100, Italy

  3. WHY SUPERCONDUCTIVY • 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

  4. HOW (we are doing it) Introduction of SC and EM with hands/minds-on, measurements carried out by sensors, modeling, simulations, … MOSEM and MOSEM2 Projects (Supercomet family projects: http://mosem.eu)

  5. European Projects MOSEM e MOSEM2 Minds-On experimental equipment kits in Superconductivity and ElectroMagnetism for the continuing vocational training of upper secondary school physics teachers 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 Partners from 11 European countries http://supercomet.no/

  6. HOW 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 MOSEM2 Projects (Supercomet family projects: http://mosem.eu) • URDF-UNIUD • USB R-T & Hallon-line acquisition and modelingTeacher Training and StudentsLearning • T/L pathsfromE.M. to SC • Active learning (strategies IBL, ProblemSolving, RTL) • Tutorialsbased on active, inquirybasedapproaches and that can promoteit.

  7. In the final version of the project, Mosem2, 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.

  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.

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

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

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

  12. The educational tools HIGH TECH KIT Hall Effect

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

  14. The educational path Magneticpropertiesof superconductor • Interactionbetweenmagnets (exploration and discussionbymeansoffieldlinesrappresentation) • Meissnereffect • E.M.induction and eddycurrents • The pinningeffect Resistivity vs temperature • Temperature dependenceofresistivityformetals and semiconductors • The Hall effect • Critical temperature for a superconductor

  15. Researchexperimentations: (since 2006) Laboratoryactivities in school (nationalplanforscientificorientation) Summerschoolsfor upper secondaryschoolstudents Preservice and in service teacher training experimentations In the last twoyears: 8 contexts (UD-PN-CS-BA-KR -SI: 295 students ) Explorativeactivities (informallearning): 4 contexts (UD-PN-Frascati- 685 students)

  16. Whichtopics in superconductivity can beintroducedbymeansof the phenomenology? • Howstudents face the mainconceptualknots?

  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 (YBa2Cu3O7), Tc ~ 90 A bath of LN A (few) magnet (A compass) (A B field probe)

  18. Preliminarexplorationwithcompasses 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) … At lower temperature … it interacts with magnets  levitation

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

  20. Are the properties of the magnet changed? • Wherever the magnet is at Te or at TNL , 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. N S S N • 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 • 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 MAGNET free constrained SUPERCONDUCTOR MAGNET

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

  24. The YBCO disk at T=TNL, evidence the property to repeal the magnet in any case ? • If the magnet is reversed, levitation occurs in the same way: in any case a repulsive effect will happen. • 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 • Yes, the YBCO evidence the property to repeal in any case a magnet

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

  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=TNL 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. Is the thefield zero inside the YBCO or just veryweak? • The samemagnetleaved over the YBCO atT=TNL levitate at the sameheight • Ifwechange the magnet the height of levitationchanges, butis the same for eachmagnet • Measurements of B just out side the YBCO • For a definedrange of the external B field the YBCO reacts to it • The currentincreaseas the magnetgoescloser to the YBCO Lab SupCond-Pigelleto

  30. A students’ outcome example • Summer School Pigelleto 8-10 sept 2010 (PLS-Università di Siena IDIFO3/MOSEM2) • Didactic Lab on SC - 3,5 h (MOSEM2 experiment ed poroposals). • 40 students (17 – 18 years old)

  31. 4 IBL Worksheetsfor the learningpath. Worksheet 1 – Interactionbetweenmagnets (discussionusingfieldlinesrepresentations) Worksheet 2 – Meissnereffect

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

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

  34. The ideas of students SC 2 – Interaction between magnetic dipoles 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? 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

  35. Summary of the results for the L path on Meissner effect • Useof the linefieldrepresentationto take into account : • The repulsion (37/40, butonethirdfollowing the magnetmagnetrepulsionscheme) • Peculiarityof YBCO (B=0) (25/40 in the rappresentation, 27/40 nin the explanations) • Changeofmagneticproperties • Featuresincluded in the explanations: • Levitation (withoutconstraints) (2/33/3) • Nullfield (2/3) • Processthathappens at the decreasingof T and itchanges the YBCO properties (40) below a threshold temperature (1/2)

  36. E.M. Induction and eddy currents

  37. Conceptualtools: • Fieldlines (operative definition) • The fluxof B ((B)) • The FNL law Bo S2(B)<MAX 2 S2 S S0(B) MAX S N 0 N S1 S 1 S1(B)<MAX 1

  38. Conceptualtools: • Fieldlines (operative definition) • The fluxof B ((B)) • The FNL law Bo • S2(B)/ t = • (S2(t) - S2(0))/ t= (S2(B) - MAX(B))/ t <0 2 S2 S S N 0 N S1 S 1 • S1(B)/ t = • =(S1(t) - S1(0))/ t= (MAX(B) - S1(B))/t >0 1

  39. Conceptualtools: • Fieldlines (operative definition) • The fluxof B ((B)) • The FNL law IindDL -F -F = Iind (LB) 2 S2 Bo F F = -(-F) S S N 0 N S1 S 1 1 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 Meissner Train “pinned”

  42. Temperature dependence of resistivity • 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)

  43. Temperature dependence of resistivity

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

  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 • Activitieshighlymotivatingthatleadtosignificantpartecipation (and learning) • Even in frontof a complexphenomenology (seeforexample the puzzlingdifferencebetween the Meissnereffect and the pinning), the students are abletoacquire the conceptualtoolsto descrive and analyze the phenomenainvolved and todevelopemodelsthat take into account the relevantaspectof the superconductivity. • Strong integrationwith “traditional” topics in E.M.

  48. The educational tools LOW TECH KIT

  49. The educational tools LOW TECH KIT

  50. The educational tools LOW TECH KIT

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