Transcript TeslaTales_SanAntoniox

Carlos R. Villa
National High Magnetic Field Laboratory
National Science Teachers Association
San Antonio, Texas
April, 2013
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One Of Three National Labs In The Southeast U.S.
One Of A Dozen High Magnetic Field Labs In The World
 Only One In Western Hemisphere
 Largest And Highest Powered In The World
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User Laboratory
 Close to 1100 User Visits in 2010
 NSF & State of Florida Funded
 Research Free To Scientist
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Research In Many Fields (Not Just Magnets!!)
 Materials Science, Physics, Engineering,
Chemistry, Biology, Biomedical, Geochemistry,
Microscopy…
Educational
component of
NHMFL’s grant
 K-12 education
outreach
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 Over 10,000 students
visited this school year
Professional
development
 Workshops and
conferences
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facebook.com/MaglabEducation
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RET program
 6 weeks in the summer
 $3600 stipend
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Gauss
 Measurement Of Magnetic
Field
 Named For Carl Friedrich
Gauss
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Tesla
 Measurement Of Larger
Magnetic Fields
 Named For Nikola Tesla
 10,000 Gauss = 1 Tesla
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Magnetism
 Ferromagnetic, paramagnetic, diamagnetic
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1820 Revolution
 Oersted & Ampere
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Faraday’s laws of induction
Lenz’s Law
Free electron theory of conduction
BCS theory of superconductivity
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Motion of electrons create magnetic fields
In some atoms, spins cancel out
 Pauli exclusion
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Whenever all electrons spin the same
direction: magnetic field is produced
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Magnetic domains
 In magnets: lined up
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Electrons tend to line up in groups (Domains)
Domains reinforce other domains
 Turn material magnetic
▪ Examples: Refrigerator Magnets, Bar Magnets, Magnetite,
Horseshoe Magnets, Hematite, etc…
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Field can be lost
 Curie Point
 Electric Current
▪ Degaussing
 Bang It
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Domains temporarily aligned
Will keep magnetic field until tampered
 Examples:
▪ Paperclips, scissors, staples, thumb tacks, pins,
screwdrivers, refrigerator door, car doors, etc…
▪ Anything that is magnetic, but will not keep its field
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No force aligning domains
 Randomly distributed
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Domains temporarily aligned by strong field
Will lose magnetic field when original field is
removed
 Examples: Aluminum can, copper wire, gold
jewelry, tungsten, etc…
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Domains temporarily
aligned by strong field
 Will align in order to
oppose original field
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Faraday’s second law of
induction
 When a material whose
atoms do not normally
have a magnetic field is
placed in a strong field,
their electrons will adjust
in such a way as to create
their own magnetic field
opposing the external one.
 WATER!
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Magnets attract and
repel
Seeing fields
 Bar magnet
 As many compasses as
possible
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Paper clips
 Argument driven inquiry
 How long will temporary
magnets hold?
▪ 36 months!
 Do they have poles?
▪ They attract and repel!
 Can they be
unmagnetized?
▪ Yes, but they can also hold
fields!
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Magnetize An Item
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Allow It To Float
 Must Turn Freely
▪ Needle
▪ Petri Dish
▪ Coffee Stirrer
▪ Water
▪ Permanent Magnet
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Superconductors are diamagnetic
 YBCO or BSSCO works well
▪ Kit available from Colorado Superconductor Inc.
An electrical current
can create a magnetic
field
 Oersted set up lecture
demonstration
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 Used battery to supply
current
 Showed compass needle
deflecting near the wire
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Deflect a compass
needle
 Battery
 Aluminum foil
 Compass
 Wire
 Assorted other items
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Place the compass:
 Above the wire
 Below the wire
Moving electrical
charges produce
magnetic fields
 Simple experiment
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 Two straight wires
 Current passed through
 Wires bowed toward or
away
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Led to electromagnets
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Materials
 Copper wire
 Iron rod (or nail)
 Battery
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Extensions:
 2 batteries
▪ In line?
 Aluminum, wooden rod
▪ Will they work?
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Right hand rule
 Direction of field (Biot-
Savart Law)
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Poles (Winding direction)
 Use compass
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Variables:
 Neatness
 Number of winds
 Wire gauge
 Battery strength
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A change in magnetic
field produces an
electric current
 Induction
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Magnetic flux: The
change needed to
induce current
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Use copper wire to
attach LED lights on a
plastic pipe.
Drop NIB magnet
through pipe (and
through copper wires)
Induction of electricity
An induced current in a
wire (by flux) will flow
to create a field that
opposes the flux
 Eddy currents created
 Used in magnetic
braking systems
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 Rollercoasters
 Electric car braking
feedback
Changing Magnetic
Flux Produces An
Induced Electric Field
 Copper Tube, NIB
Magnet
 Eddy Currents
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Electrical conduction in a solid is caused by
the bulk motion of electrons
 Each metal atom contributes an electron that is
free to roam
 Voltage briefly accelerates the electrons
▪ Resistance is friction
 Each electron is everywhere
▪ Like a wave in a pool
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Current electricity
 Electrons flow through a wire
▪ Slow movement
 Circuit needed
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Complete circuits using Alien Ball
Turn on the light bulb
 Turn on two light bulbs
 Create more advanced circuits
▪ Parallel & series
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BCS: Bardeen, Cooper, Schreiffer
At low temperatures, some metals lose
resistance
 Atoms nearly stationary
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Superconductivity results from the formation of
Cooper pairs
 Two electrons partnered
 One follows the other
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Results in frictionless
flow of electrons
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Repeat Ampere lab
Measure resistance with digital multimeter at
each step
 Raise temperature with hot water
 Lower temperature with ice water
 Lower temperature with liquid nitrogen*
• Always adhere to safety guidelines
• Goggles, Cryogenic gloves, and covered footwear
STOP FAKING IT:
ELECTRICITY & MAGNETISM
DRIVING FORCE: THE NATURAL
MAGIC OF MAGNETS
BILL ROBERTSON
JAMES D. LIVINGSTON
A SHORT HISTORY OF
NEARLY EVERYTHING
BILL BRYSON
THE NATURE OF SCIENCE
JAMES TREFIL
HIDDEN ATTRACTION: THE
MYSTERY & HISTORY OF
MAGNETISM
GERRIT L. VERSCHUUR
THE COLD WARS: A HISTORY
OF SUPERCONDUCTIVITY
JEAN MATRICON & GEORGES
WAYSAND
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http://education.magnet.fsu.edu
 MagLab Alpha; Science, Optics, & You; other
curriculum
 MagLab audio slideshows
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RET Program
K-12 Programs
MagLab Educator’s Club
Carlos R. Villa
National High Magnetic Field Laboratory
[email protected] • 850-644-7191