Transcript SuperconductivityICP..>

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
[email protected], [email protected] , [email protected]
Layout
- Intro: SC in HS and RQ
- The context
- Instruments & methods
- Students learning
- Conclusions
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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, 352-9.
[2] Gil, D. P., Solbes., J. (1993). The introduction of modern physics. IJSE, 15, 255-260.
[3] Hake R.R. (2000). Is it Finally Time to Implement Curriculums?, AAPT Ann. 30(4), 103.
Michelini,
Stefanel, Vanacore[4] Badía-Majós
A (2006) Understanding stable
levitation
of SC, AJP 74 (12), 1136-1142.
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[5] Ostermann, F., Ferreira, L.Cavalcanti, C (1998). Rev. Bras. de Ensino de Fís. 20, 270-288.
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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, 176-9.
[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, 847-851.
[9] Gough, C. (1998). High T SC take off. Phys. Educ., 33, 38-46.
[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, 391-404.
[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,
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http://lsg.ucy.ac.cy/girep2008/intro.htm
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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, 221-229.
[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,
http://www.fisica.uniud.it/URDF/mptl14/contents.htm
[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.190-196
[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
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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)
School experimentation
in a class of 15 students
(18 aged)
4 Tutorial worksheets
Pre-post test
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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
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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?
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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
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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
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HIGH TECH KIT
Persistent
currents
Para-Ferromagnetic
transistion (gandolynium)
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Levitation
pinning
The MAGLEV train
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Levitation and induction
V=0
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V= cost0
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Field
lines
S
N
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Conceptual references for
the phenomenological
analysis
Magnetization dipole
momentum vector
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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
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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
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Monitoring tools: home-work
Concerning the Meissner effect:
A) What do you observed?
B) 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
Michelini,
Stefanel,dipole
Vanacore-evetually present
Draw with aanother coulor the
magnetic
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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?
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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
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(4/15
"Attraction; weak attraction;
repulsion")
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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.
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
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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).
(11/15)
The response of the material at the
approach of the magnet is a strong
repulsion, in fact the levitation occurs
(4/15)
The sample of YBCO becomes
diamagnet and a small magnet
placed above remains suspended
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WS1 - Magnet and YBCO at T=TNL: how change the interaction?
Is recognized by all the sharp change in the interaction YBCOmagnet ....
…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.
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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?
A) It is no more crossed by th field lines (3/15);
B) ro=0 (4/15)
C) T decreases (4/15)
D) It acts as a magnetic screen (4/15)
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Home work – about the Meissner effect
Concerning the Meissner effect:
A) What do you observed?
B) Explain in term of field lines and/or magnetic dipole momentum vector
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)
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Concerning the Meissner effect: Home work – about the Meissner effect
A) What do you observed?
B) 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
A Tenv Wthe YBCo is crossed
by the magnetic field lines.
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When the YBCO reached the Tc
becomes superconducting and
Michelini, Stefanel, Vanacoreexpels the field lines.
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Home work – about the Meissner effect
Concerning the Meissner effect:
A) What do you observed?
B) 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»
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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”.
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Post test
2/15
“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”.
3/15
Having no resistivity it will not interact with the field and
therefore it cannot will have one.
4/15 No answer.
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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)
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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
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Conclusions
• www.fisica.uniud.it/URDF
• http://www.fisica.uniud.it/mosem/indice.htm
• mosem.eu
• http://media.mosem.eu/
• [email protected],
[email protected]
• [email protected]
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Thank you
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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.
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
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Meissner
effect prevails.Michelini, Stefanel, Vanacore’16
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