In this lesson
students supposed to work with computers. However id there is not available
computers that teachers can use in physics class three videos can be watched
one by one. Videos are short, so it possible to do it in one lesson. While
students presenting their ideas teacher might assess each group according to
the poster rubrics:
All requirements present well written
text and carefully chosen visuals work together to illustrate and inform
about poster subject
All requirements present, descriptive
text and appropriate visuals work together to inform viewers
Most requirements present, text contains
some inaccuracies or lacks organization or impact, inappropriate or missing
Requirements missing poorly written
inaccurate or insufficient text and or visuals or “cut & pasted” text.
Followed layout sample, logical and easy
to read text and visuals, neatly designed layout compliments content
Followed layout sample, logical text and
visuals that are neat and easy to understand
Followed layout sample, somewhat
Did not follow layout sample
disorganized hastily and carelessly planned
Pleasing use of color, shapes, symbols
and other graphic elements captures viewers’ attention and interest
Good use of color and eye-catching
Graphics have clustered appearances or
are sparse (too much empty space)
Little constructive use of color or
Incorporates unique and pertinent ideas
design elements, visuals or text that make the poster stand out
Contains some unique or imaginative
Contains some good, although not
entirely original elements
evidence or creativity
There is a useful arcticle about the
physics of superconductivity:
discover flaws in superconductor theory
This image of a magnet levitated over a high-temperature
superconductor array shows rectangular TFMs (black) levitating a heavy
ferromagnet (silver) above a container of liquid nitrogen.
The basic property of superconductors is
that they represent zero "resistance"
to electrical circuits. In a way, they are the opposite of toasters, which
resist electrical currents and thereby convert energy into heat.
Superconductors consume zero energy and can store it for a long period of time.
Those that store magnetic energy —known as "trapped field magnets" or
TFMs—can behave like a magnet.
the Journal of Applied Physics, the researchers describe
experiments whose results exhibited "significant deviations" from
those of the Critical State Model. They revealed unexpected new behavior
favorable to practical applications, including the possibility of using TFMs in
myriad new ways.
Much of modern
technology is already based on magnets. "Without magnets, we'd lack
generators [electric lights and toasters], motors [municipal water supplies,
ship engines], magnetrons [microwave ovens], and much more," said Roy
Weinstein, lead author of the study, and professor of physics emeritus and research
professor at the University of Houston.
Generally, the performance of a device based on magnets improves
as the strength of the magnet increases, up to the square of the increase. In
other words, if a magnet is 25 times stronger, the device's performance can
range from 25 to 625 times better.
TFMs are clearly
intriguing, but their use has been largely held back by the challenge of
getting the magnetic field into the superconductor. "A more tractable
problem is the need to cool the superconductor to the low temperature at which
it super conducts.
"Bean assumed the superconductor had zero resistance and
that the basic laws of electromagnetism, developed circa 1850, were
correct," Weinstein said. "And he was able to predict how and where
an external magnetic field would enter a superconductor."
The method widely
used today is to apply a magnetic field to a superconductor via a pulse field
magnet after the superconductor is cooled. Bean's model predicted, and until
now experiments confirmed, that to push as much magnetic
field as possible into a superconductor, the pulsed field must
be at least twice as strong, and more typically over 3.2 times as strong, as
the resulting field of the TFM.
But, this severely
limits the applicability of TFMs. "It's difficult and expensive to produce
fields of more than 12 tesla," said Weinstein. "If Bean's theory held
true, this cost and practicality barrier would limit TFMs used within products
to a maximum of typically 3.75 tesla."
Minor problems with
Bean's Critical State Model emerged shortly after it was published, according
to Weinstein. Any chink in theoretical armor is worthy of an exploratory
experiment, and this is what motivated Weinstein and his colleagues.
They discovered that for certain constraints on a magnetic
pulse, Bean's model is far off base, and a significantly different spatial
distribution of field occurs. "Great increases in field occur suddenly, in
a single leap, whereas Bean's model predicts a steady, slow increase,"
"By using our newly discovered methods, the maximum TFM
field is now 12 tesla," said Weinstein. "A motor, if made in a fixed
size, can produce 3.2 times the torque. Alternatively, the motor can be
designed to produce the same amount of torque, but have its volume reduced by
more than 10 times. This reduction in materials can result in great cost
The researchers are
still within the "early days" of this work and have already disproven
their first thoughts concerning what is causing their results. "We're now
essentially spelunking in a dark cave without lights—it's frustrating, but
exciting," Weinstein said.
In terms of
applications for their discovery, the researchers suggest the ability to
replace a $100,000 low-temperature superconducting magnet in a research X-ray
machine with a $300 TFM, or possibly replace a motor with one that is a quarter
of the size of an existing one. There are many other potential applications,
such as an energy-efficient ore separator, noncontact magnetic gears that will
not wear or require repair, a red blood separator with 50 percent improved
yield, and even an automated docking system for spacecraft.
colleagues are now searching for fast, short-term support that will allow them
to continue their research to explain this new phenomenon. "While we now
know enough to apply our new discovery to significantly improve a large number
of devices, we don't yet fully know what's going on in terms of the basic laws
choice questions with answers on topic Superconductors
happens to current sent through a superconducting wire?
gains a slight voltage boost.
B)It's transmitted without loss of energy.
experiences a sharp voltage drop.
have zero resistance, so current sent through such a wire loses no energy.
Diderik van der Waals
C)Heike Kamerlingh Onnes
physicist Heike Kamerlingh Onnes and his collaborators, Cornelis Dorsman,
Gerrit Jan Flim and Gilles Holst discovered superconductivity. The research of
Johannes Diderik van der Waals -- a fellow countryman and contemporary physicist
famous for the forces, molecules, radii and equation of state that bear his
name -- helped inspire Onnes’ work. Hugo Christiaan Hamaker, another Dutch
scientist, was an experimental physicist famous for his statistical work.
what year did Onnes discover it?
it was first identified by Dutch physicist Heike Kamerlingh Onnes in 1911,
superconductivity flew in the face of established physics. In fact, an entirely
new kind of physics, quantum mechanics, would have to be established before
anyone had a hope of cracking the mystery of how the phenomenon worked.
how cold do conventional superconductors have to get before they enter the
K (minus 273.2 C, minus 459.7 F)
B)39 K (minus 234 C, minus 390 F)
K (minus 143 C, minus 226 F)
only function at very cold temperatures, on the order of 39 K for conventional
superconductors (the solid mercury wire that Kamerlingh Onnes used had to be
cooled below 4.2 K) and below around 130 K for modern, high-temperature
superconductors. As for absolute zero, it cannot be achieved artificially,
although laser cooling has taken us within one billionth of a degree of it.
cease being superconductors if they are exposed to which of the following?
large of a magnetic field
C)Both are correct.
as superconductors have a critical temperature that separates them from normal
conductors, they also have a critical magnetic field that hits them like
kryptonite. Too much current will also take superconductors from hero to zero.
of the following do NOT currently use superconductors?
low critical magnetic fields limited the usefulness of older Type I
superconductors for magnetic applications, modern Type II superconductors, such
as niobium-titanium (NbTi), can handle much higher magnetic loads. Because they
produce higher magnetic fields than, say, electromagnets made from copper wire,
they have proven invaluable in MRI machines and proton accelerators.
well a material conducts electricity has to do with what factor?
easily its component atoms give up electrons
availability of free electrons to carry current
C)both A and B
electrical conductors have atomic structures that readily give up electrons,
moving them from the valence energy level to the conductance energy level. The
result is a large number of free electrons available to carry current. Thus, the two
answers essentially describe the same thing.
can describe the structure of a typical conductor as which of the following?
A)a lattice of atoms
series of tubes
bevy of bosons
conductor is composed of a lattice of atoms, like a tiny jungle gym in which
the intersections represent atoms and the connecting rods stand in for
interactive forces. A bevy of bosons would be a boon to behold, but bears no
relation to a typical conductor. Thanks to Alaskan Sen. Ted Stevens, everyone
knows that the Internet is a series of tubes.
of the following is NOT a source of resistance in a typical conductor?
more deformed the lattice of the material is, the more likely it is that it
will interfere with the free flow of electrons. The same is also true for
higher temperatures, which cause the lattice and its component atoms to vibrate
and oscillate faster. Cold,
as a rule, decreases resistance.
happens to a superconductor when it is cooled to its critical temperature?
abruptly loses all resistance.
undergoes a phase transition.
C)Both are correct
a superconductor is cooled, its resistance gradually drops until the critical
temperature is reached, after which all resistance abruptly disappears. The
substance has undergone a phase transition from conventional material to
are Cooper pairs?
on the periodic tale that share the same conductance
of metals that make good superconducting alloys
C)linked electrons that help explain superconductivity
a superconductor, two electrons pair off to gain a net advantage when dealing
with the ions that make up the material lattice. As the electron passes through
the positively charged lattice, it attracts the surrounding atoms toward it. As
they bunch up, these atoms create a local area of higher positive charge, which
increases the force pulling the second electron forward. Consequently, the
energy spent to get through, on average, breaks even.
is the name of the theory that explains how conventional superconductors work?
B)the BCS theory
were known for almost half a century before, in 1957, physicists John Bardeen,
Leon N. Cooper and John Robert Schrieffer finally advanced a theory that
worked. In their honor, this fundamental theory of superconductivity is
generally known as the Bardeen-Cooper-Schrieffer, or BCS, theory. In case
you're wondering, XTC was a New Wave band from Swindon, England, and "The
Aquitaine Progression" was a book by Robert Ludlum, but it sounded cool.
superconductors that fit the BCS model are called "classical." What's
the designation for superconductors that do NOT jibe with this theory?
a decade or two of the BCS theory being published, researchers began
discovering other superconductors, such as heavy-fermion systems and
high-temperature superconducting cuprates that broke the model. Today,
superconductors that fit the BCS model are called “classical,” while those that
don’t are known as "exotic." The means by which these exotic
superconductors operate remains the subject of hot debate. "Strange"
and "top" are designations used to describe quarks.
of the following elements become superconductors at low temperatures and
silicon and uranium
B)aluminum, lead, mercury and tin
cobalt, iron, manganese and nickel
of materials, including 27 metallic elements -- such as aluminum, lead, mercury
and tin -- become superconductors at low temperatures and pressures. Another 11
chemical elements -- including selenium, silicon and uranium -- transition to a
superconductive state at low temperatures and high pressures. The magnetic
elements chromium, cobalt, iron, manganese and nickel are not superconductors.
superconductors are what type of material?
A)alloys or compounds
vast majority of superconductors are alloys or compounds.
type of superconductor exhibits perfect diamagnetism in every superconducting
of the above
cooled below its critical temperature, a Type I superconductor not only
exhibits zero electrical resistivity, it also displays perfect diamagnetism.
Type II superconductors display perfect diamagnetism while in one
superconducting state but not in the other.