Exploration of students’ ideas on superconductivity

Exploration of students’ ideas on superconductivity
Marisa Michelini1, Alberto Stefanel1 and Antonio Vanacore1,2 1Research Unit in Physics Education, University of Udine, Italy 2University of Salerno, Italy ,

Michelini, Stefanel, Vanacore- Superconductivity
Layout - Intro: SC in HS and RQ - The context - Instruments & methods - Students learning - Conclusions aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

Superconductivity is an important context in order to be brought in the high school because: relevant applications [1-3] can be interpreted on different levels [4-5]. Therefore it can be integrated in ordinary electromagnetism programs in high schools in order to renew the school curricula expanding areas of physics of the twentieth century and rethinking the ordinary curriculum. [1] Aubrecht, G. (1989). Redesigning courses and textbooks for the 21century. AJP, 57, [2] Gil, D. P., Solbes., J. (1993). The introduction of modern physics. IJSE, 15, [3] Hake R.R. (2000). Is it Finally Time to Implement Curriculums?, AAPT Ann. 30(4), 103. [4] Badía-Majós A (2006) Understanding stable levitation of SC, AJP 74 (12), [5] Ostermann, F., Ferreira, L.Cavalcanti, C (1998). Rev. Bras. de Ensino de Fís. 20, aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

Several simples apparatuses were designed for example to show the magnetic levitation in a didactic laboratory [6-9] . Few studies have been done about pupils 'learning in this area. For several years has been developing a project for the teaching and learning of superconductivity in high school that led us to design and test educational courses that integrate the superconductivity in' electromagnetism [10-12]. [6] Guarner, E., Sánchez, A.M. (1992). The SC bird: a didactical toy. The Phys.Teach., 30, [7] Brown, R. (2000). Demonstrating the Meissner Effect, The Physics teacher, 38 (3) S. 168. [8] Strehlow, C. P., Sullivan, M. C. (2009). A Classroom Dem. of Levitation, AJP 77, [9] Gough, C. (1998). High T SC take off. Phys. Educ., 33, [10] González-Jorge H., Domarco G. (2004). SC - current induction, Phys. Educ. 39, 234 [11] Ostermann, F.; Moreira, M.A. (2000b). Rev. de Ens. de las Ciencias, 3 (2), 18, [12] Corni F, Michelini M, Santi L, Stefanel A, Viola R (2009) Curricular Paths in the Supercomet2 Experimentation in Italy, in Physics Curr. Design, Constantinou CP, Papadouris N eds, aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

In the context of the Italian collaboration of the Supercomet family European projects, educational paths were designed, implementing superconductivity in the electromagnetism curriculum of upper secondary school [13-14]. In particular a USB apparatus was developed for the measurements of the breakdown of resistivity at phase transition [15] Several experimentation were conducted in Italian high schools [16-17] [13] Greczylo, T., Bouquet, F., Ireson, G., Michelini, M., Engstrom, V. (2010). High-Tech Kit, Il Nuovo Cimento C, (33) 3, [14] Kedzierska E. et al. (2010). Il Nuovo Cimento, 33 (3) 65-74 [15] Gervasio, M., Michelini, M. (2010). A USB probe for resistivity versus temperature, [16] Viola R, Michelini M, Santi L, Corni F (2008) The secondary school experimentation of Supercomet in Italy, in R.J.Sepic et al eds., Girep-Epec, Zlatni. Rijeka (CRO) pp [17] Stefanel A., Michelini M., Santi L. (2012) High school students analyzing the phenomenology of SC, in Tasar F.ed., sel. Paper of World Conference on Physics Education aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

Here a study carried out in a high school is presented. The study is a part of the doctoral PhD research project of one of us (A. Vanacore) 7:30 hours (+ pre-post test) Prerequisite: magnetic interaction, magnetic field and flux, EM induction. The path: magnetic properties of matter, Magnetic properties of YBCO Meissner and pinning effect School experimentation in a class of 15 students (18 aged) 4 Tutorial worksheets Pre-post test aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

Rsearch Questions RQ1. How student characterize the SC levitation? RQ2. What conceptual reference use they in their description? RQ3. How they characterize the Meissner effect? aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

before the experimentation: the students followed an ordinary triannual physics course (3 h per week) based on lectures only, never having had any (direct or indirect) laboratory experience They studied the EM phenoma, the magnetic properties of material , the em induction phenomena. In the previous evaluation of the teacher: a class of middle level aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

The steps of the educational path followed: A) Interaction of a neodimium magnet and Ferromagnetic objects Non ferromagnetic objects Bipolar nature of magnetic field source Para/diamagnetic properties of materials B) Interaction of an YBCO disc and a magnet (T=To and T=TNL) Magnetic properties of a SC Meissner effect as R=0, B=0 C) The pinning effect & distinction Meissner/pinning aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

Para-Ferromagnetic transistion (gandolynium)
HIGH TECH KIT Persistent currents Levitation pinning Para-Ferromagnetic transistion (gandolynium) The MAGLEV train aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

Levitation and induction V= V= cost0 aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

Field lines Conceptual references for the phenomenological analysis Magnetization dipole momentum vector S N aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

Monitoring tools: tutorial worksheets for students Magnetic properties of materials Magnetic properties of YBCO at T=Tenv Field lines of a magnet and a YBCO at T=Tenv aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

Monitoring tools: tutorial worksheets for students A magnet and a YBCO at T=TLN Magnetic properties of a YBCO at T=TLN Levitation and magnetic field lines at T=TNL aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

Monitoring tools: home-work Concerning the Meissner effect: What do you observed? Explain in term of field lines and/or magnetic dipole momentum vector Monitoring tools: Post test: Field lines and magnetic dipole momentum vector in the case of an R=0 conductor A cylinder with R=0 is inserted in an omogenous magnetic field Draw the configuration of the resultnt B field Draw with aanother coulor the magnetic dipole evetually present aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

Analysis of the responses categorizing; the interpretative responses (which elements of the sci model) The descriptive one (which aspects) Naive responses (typical students answers) How students analyze the T=TNL situation? How students characterize the Sc state? How students characterize the Meissner effect? How students characterize the pinning effect and distinguish from the Meissner effect? aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

Classification of the magnetic properties of materials:
WS1 - Magnetic properties of materials Classification of the magnetic properties of materials: Criterion A - “to become" good or not good magnets (7/15 – ferro "become good magnets, attraction is strong”; para- “it remain weak magnet”; dia-”weak magnetic field") Criterion b) The field lines, Magnetic dipole vector, Effect (attraction/rep) (4/15) Criterion c) Type of interaction with a magnet (4/15 - "Attraction; weak attraction; repulsion") The criteria are usually unable to characterize univocally the type of material Only 1/4 students integrate: - the phenomenon - the interaction model - the magnetic properties model aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

(suspending it at the extremity of a yoke).
WS1 - Magnetic property of a YBCO at T=Tenv The classification of the YBCO at T=Tenv was done analyzing the type of interaction with a magnet under appropriate conditions (suspending it at the extremity of a yoke). All recognize the paramgnetic nature of YBCO at Tenv. There is not permanent magnetiation in the case of para and dia magnetism  More stress on this aspect the material suspended in a suitable structure is paramagnetic (attracted by the magnet) and lets the field lines pass. 8/15: it leave pass the field lines 7/15: YBCO is a "variable magnetism“ material, highlighting that the magnetic properties emerge only in the presence of a magnet aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

The student stress one aspect per time
WS1 - Magnet and YBCO at T=Tenv: field lines representation All students represent the field lines of the magnet outside of it, including the inner zone of the YBCO. In most cases, the YBCO does not influence the field (11/15), in some cases, it influence the field, but it is not clear how (4/15). via modelling link the magnetic properties of the YBCO and the resulting interaction with a magnet The student stress one aspect per time The continuity of the field lines inside the magnet do not emerge from phenomenology more stress about dipolar nature of magnets The response of the material at the approach of the magnet is a strong repulsion, in fact the levitation occurs (11/15) (4/15) The sample of YBCO becomes diamagnet and a small magnet placed above remains suspended aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

Students looks qualitatively at phenomena.
WS1 - Magnet and YBCO at T=TNL: how change the interaction? Is recognized by all the sharp change in the interaction YBCO-magnet .... …emphasizing the following aspects: in over 2/3 of the sample (11/15) is shown the obvious repulsion stressing often that this is due to the change of the properties YBCO (7/11); the remaining (4/15) emphasize the presence of an attractive effect [the residue pinning effect still present in this type of superconductors], in some cases adding that are the properties of the magnet to be changed. Students looks qualitatively at phenomena. The Meissenr effect is always present with the pinning effect in the YBCO sample modelling for many student the stability of levitation is the crucial aspect to understand….this require the analysis of the geometry, the analysis of the two effects together…  aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

Students looks to one aspect per time they need integration
WS1 - Magnet and YBCO at T=TNL: how change the properties of the YBCO? Everyone recognizes that the properties of YBCO changed: "from paramagnet to diamagnet" (8/15) It becomes superconducting (4/15) It insulate magnetically (3/15)). In which way? It is no more crossed by th field lines (3/15); ro=0 (4/15) T decreases (4/15) It acts as a magnetic screen (4/15) Students looks to one aspect per time they need integration aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

ferromagnetismparamagnetism
Home work – about the Meissner effect Concerning the Meissner effect: What do you observed? Explain in term of field lines and/or magnetic dipole momentum vector ferromagnetismparamagnetism The caracterization of the magnetic properties based only on one aspect do not discriminate between materials 2/3 outline the characteristics of YBCO at Tamb (a powerful magnet attracts two tablets of YBCO hung at the ends of a wooden yoke suspended). According to the repulsion observed between YBCO and magnet students have ranked the YBCO as paramagnet (6/15), as ferromagnet (4/15) aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

Home work – about the Meissner effect Concerning the Meissner effect: What do you observed? Explain in term of field lines and/or magnetic dipole momentum All analyze what happens at T=TNL 6/15 – «The levitation observed indicates that the properties of YBCO have changed. Since the effect is repulsive it follows that it has become diamagnetic”. 5/15 - The YBCO becomes diamagnetic, in three cases, adding that r = 0, and this is the origin of the phenomenon of the levitation of the magnet 2/15 - the YBCO repels the magnet with a force that is equal to the weight force. 2/15 - the YBCO becomes diamagnetic A total of 12/15 recognize the diamagnetism of YBCO Model from experience or experience guided by model? A Tenv Wthe YBCo is crossed by the magnetic field lines. When the YBCO reached the Tc becomes superconducting and expels the field lines. aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

Home work – about the Meissner effect Concerning the Meissner effect: What do you observed? Explain in term of field lines and/or magnetic dipole momentum In 8/15 also include an explicit explanation in terms of field lines. 5/8 that the YBCO at T Tamb was passed by field lines (was paramagnetic) in TNL it expels the field lines, in 3 cases adding that this is due to surface currents 2/8 the field lines do not cross over the YBCO, the YBCO screened the field lines 1/8 field lines trapped 3/15 it becomes diamagnetic 1/15 «this effect [levitation] names Meissener effect» Overcome the descriptive tendence  construct conceptual interpretation of/though formalism (different step) aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

Post test 6/15 “Having resistivity = 0, we can say that the material is a superconductor. This means that achieves a perfect diamagnetism: therefore generates a magnetic moment that is opposed to the external magnetic field, so as to completely expel, Inside not have field lines”. aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

Missing link: field lines and magnetic dipole momentum
Post test “A material with no resistivity is a body in which all the domains are oriented toward the magnetic field in which it is immersed and then the resulting magnetic field is equal to the external lines and heading to the right then the north pole of the body will be at the left and the South on the right. the vector magnetic dipole will have a direction parallel to the magnetic field and the opposite direction”. 2/15 Missing link: field lines and magnetic dipole momentum Having no resistivity it will not interact with the field and therefore it cannot will have one. resistencefriction 3/15 No answer. 4/15 aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

Conclusions Need to rinnovate curricula SC is a challenging phenomenological context important both for technological application, both on the theoretical point of view, both to bridge from classical to quantum physics Experimentations with 375 students A 7.5 h research experimentation was conducted in a class of 15 students (18 years hold) to go deep in the students learning process (Work-Sheets; pre-post test; Home-work) aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

Conclusions RQ1. How student characterize the SC levitation? Repulsion Forces equilibrating weight Attraction (attention to the stability) RQ2. What conceptual reference use in their description? Magnet momentum in opposite direction Diamagnetic nature of YBCO B=0 and no field line inside, expulsion of the field lines Link with ro=0 only for few students On the contrary: r=0 conductortransparent conductor RQ3. How they characterize the Meissner effect? - Repulsion in any case; diamagnetism, magnetic dipole vector aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

Conclusions mosem.eu Thank you aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

WS2 – Pinning effect L'effetto pinning è stato da tutti caratterizzato evideniando che "il magnete resta attaccato all'YBCO", differenziandolo nella maggior parte dei casi dall'effetti Meissner in quanto tale effetto si manifetsa sempre in una repulsione, sia che il magnete sia inizialmente sull'YBCo, sia che venga portato dopo che T=TNL.. Nei SC che manifetsano effetto pinning, se la Sc è creata lontano dal SC il magnete viene responto, altrimenti resta "attaccato" Inoltre per 12/15 l'effetto Meissener è comunque presente, ma prevale l'effetto pinning. Students identificate Pinning effect and distinguish phenomenologically from Meissner effect Do not contruct coherent model in term of field lines. Se hai YBCO potenziato non riesco a separarli perché prevale il pinning, al contrario con L’YBCO normale si staccano perché prevale l’effetto Meissner. If you have upgraded YBCO, I can not separate them because the pinning prevails, in contrast with the normal YBCO come off because the Meissner effect prevails. aprile ’18 Michelini, Stefanel, Vanacore- Superconductivity

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