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Secondary students learn superconductivity from
phenomenology
Marisa Michelini, Lorenzo Santi, Alberto StefanelResearch Unit in Physics Education
University of Udine (Italy)[email protected], [email protected]
19 apr 2023 Michelini, Stefanel - Superconductivity 2
Experimentation performed by teachers in school
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Research Experimentation performed by researcher or teachers/researcher in school
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RQ1. The phenomenological exploration of SC levitation can produce a more effective understanding of eltectromagnetic processes?RQ2. The analysis of ideal cases what kind of spontaneous model activate in pupils?RQ3. Are these model modified through a phenomenological exploration?RQ4. Which knots remain open?
Rsearch Questions
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School experimentation in a class of 16 students (18 aged)
12 Tutorial worksheetsPre-post test
10 hours + 2 pre/post test
A path on magnetic interaction, magnetic field and flux, magnetic properties of matter, SC:-integrated in the ordinary curruculum-defined in accordance with the class teacher-implemented during the regular school week
A) Magnet-objects interactionB) Interaction of a neodimium magnet and
619 apr 2023 Michelini, Stefanel - Superconductivity
Ferromagnetic objectsNon ferromagnetic objectsBipolar nature of magnetic field source
Para/diamagnetic properties of materials
E) Interaction of an YBCO disc and a magnet (T=To and T=TNL)F) Comparison with other interaction:
Magnetic properties of a SC
Peculiarity of SC levitation
G) Exploration of stability of levitation
C) Current and magnetic field
D) Changes in time of the magnetic field and the EM induction
Role of em induction
H) Breack down of resistivity Meissner effect as R=0, B=0
The steps of the educational path followed:
Eddy corrents in magnet falling on/inside conductor
Michelini, Stefanel - Superconductivity 719 apr 2023
Gervasio M, Michelini M (2010), http://www.fisica.uniud.it/URDF/mptl14/contents.htm
A- «Slowed down motion because of the induced current»; «induced currents that repeal the magnet»B- “muffled motion” [it falls as on a pillow]
(p<0.01)
Q9. A disc magnet, such as that shown in the figure, is falling on a thick layer of Cu.9.1 Will be influenced the falling motion of the magnet by the presence of the Cur layer? explain
C – “Cu have low resistivity then it attracts the magnet more fast”D – “Yes, bust just very few, because Cu is diamagnetic” NA – No answer
9.3. It is possible that for some appropriate geometry of the Cu layer and the magnet, i.e. to a suitable magnet can be realized the situation in which the magnet is stationary and remains suspended above the plate? Explain your answer
A. No, the effect in not persistent without change
B. No, because R0C. NO
D. Yes, with an opportune geometry of the systems
E. Yes for particular magnetF. Yes, if Fm>Fp
P<.01
A: would remain suspended / levitating (in 4 cases: perfect diamagnet)B: The phenomena of repulsion would be strongerC: Yes, why he does not repel the magnet so that would not diminish its speed.
9.4. Would it change anything if you replace the Cu layer with a layer with zero resistance?
P<.01
Q10. When a cilindrical magnet falls down inside a conductor tube (i.e a Cu tube), after a brief accelerated phase, it falls down at constant velocity10.1 How it can be explained the phenomenon?
A : Because of the induced electric current
B: Due to the generated field and the related resistence
C: Presence of the electrical resistence in the tube and related Joule effect
Cu v(t)constant
D: the conductor, having a resistance, acts on the magnet slowing the fall
E: Friction due to the contact of the tube and the magnet
NA: No answer
P<.05
Cu v(t)costante YBCO=0 v(t)?
Q10. When a cilindrical magnet falls down inside a conductor tube (i.e a Cu tube), after a brief accelerated phase, it falls down at constant velocity10.2. It will be change something if the conductor have a null resistance? Explain
A: It remain suspended/trapped (no dissipation)
B: No Joule effect
C: No induced currentD: free fall (nothing it is opposed to
the falling downNA : No answer
P<.05
Induced currentInduced current
9 cases
Diamagnetic properties of Cu motivation
Free fall
1 cases
10/16 9/16
1/16 7/16
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A)
B)
C)
D)
E)
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Q12. Consider the case in which within a uniform magnetic field is posed a cylinder composed by material whose resistivity is nothing.Draw:12.1 with a blue pen, the configuration of the resulting magnetic field;12.2 with a red pen. the possible magnetic dipole of the cylinder.
Lines inalteredLines repelled
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10/16 8/16In 6 cases
4/16
8/16
In 3 cases
Less density
No deviation
9.2. Represent with opportune vectors the magnetic dipole moments that may eventually be present in the two systems.
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Q10. When a cilindrical magnet falls down inside a conductor tube (i.e a Cu tube), after a brief accelerated phase, it falls down at constant velocity10.1 How it can be explained the phenomenon?
Cu v(t)constant
A : Because of the induced electrical current (Sub-chategories):
A1) The passagge of the magnet produces a flux variation in the tube. The flux variation cause the induction of an electric current. The induced current generate a field of opposite direction with respect of the first. When the two forces are equal in module the velocity in the motion is constant (1 1)A2) Flux variation, creation of an induced current, that cause the magnet slowing down/that contrast the weight force (33)A3) The induced current creates Joule effect (energy dissipation) (04)A4) The magnet motion inside the cylinder produce parasite current and therefore a magnetic field that contrast the accelerated motion (01)
