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Tesla TalesCarlos R. VillaNational High Magnetic Field Laboratory
National Science Teachers AssociationSan Antonio, TexasApril, 2013
NHMFL Overview
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
NHMFL Overview
User Laboratory Close to 1100 User Visits in 2010 NSF & State of Florida Funded Research Free To Scientist
Research In Many Fields (Not Just Magnets!!) Materials Science, Physics, Engineering,
Chemistry, Biology, Biomedical, Geochemistry, Microscopy…
Center for Integrating Research & Learning
Educational component of NHMFL’s grant
K-12 education outreach Over 10,000 students
visited this school year
Professional development
Workshops and conferences
facebook.com/MaglabEducation
Special Opportunity - RET 2013
RET program 6 weeks in the
summer $3600 stipend
Magnet Review
Gauss Measurement Of
Magnetic Field Named For Carl
Friedrich Gauss Tesla
Measurement Of Larger Magnetic Fields
Named For Nikola Tesla
10,000 Gauss = 1 Tesla
Tesla Tales
Magnetism Ferromagnetic, paramagnetic,
diamagnetic 1820 Revolution
Oersted & Ampere Faraday’s laws of induction Lenz’s Law Free electron theory of conduction BCS theory of superconductivity
Magnetism
Motion of electrons create magnetic fields
In some atoms, spins cancel out Pauli exclusion
Whenever all electrons spin the same direction: magnetic field is produced
Magnetic domains In magnets: lined up
Ferromagnetism: Permanent Magnets
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…
Field can be lost Curie Point Electric Current▪ Degaussing
Bang It
Ferromagnetism: Temporary Magnets
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
Paramagnetism: Temporary Magnets
No force aligning domains Randomly distributed
Domains temporarily aligned by strong field
Will lose magnetic field when original field is removed Examples: Aluminum can, copper wire,
gold jewelry, tungsten, etc…
Diamagnetism: Counter Aligned Magnets
Domains temporarily aligned by strong field Will align in order to oppose
original field 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!
Ferromagnetism Lab: Magnetic Fields
Magnets attract and repel
Seeing fields Bar magnet As many compasses
as possible
Ferromagnetism Lab: Temporary Magnets
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!
Ferromagnetism Lab: Compass Creation
Magnetize An Item Allow It To Float Must Turn Freely▪ Needle▪ Petri Dish▪ Coffee Stirrer▪ Water▪ Permanent Magnet
Diamagnetism Lab
Superconductors are diamagnetic YBCO or BSSCO works well
▪ Kit available from Colorado Superconductor Inc.
1820: Oersted Discovery
An electrical current can create a magnetic field
Oersted set up lecture demonstration Used battery to
supply current Showed compass
needle deflecting near the wire
Oersted Lab
Deflect a compass needle Battery Aluminum foil Compass Wire Assorted other items
Place the compass: Above the wire Below the wire
1820: Ampere’s Law
Moving electrical charges produce magnetic fields
Simple experiment Two straight wires Current passed
through Wires bowed toward
or away Led to
electromagnets
Ampere Lab
Materials Copper wire Iron rod (or nail) Battery
Extensions: 2 batteries▪ In line?
Aluminum, wooden rod▪ Will they work?
Ampere Lab: Part II
Right hand rule Direction of field (Biot-
Savart Law) Poles (Winding
direction) Use compass
Variables: Neatness Number of winds Wire gauge Battery strength
1831: Faraday’s Laws
A change in magnetic field produces an electric current Induction
Magnetic flux: The change needed to induce current
Faraday Lab
Use copper wire to attach LED lights on a plastic pipe.
Drop NIB magnet through pipe (and through copper wires)
Induction of electricity
1835: Lenz’s Law
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 Rollercoasters Electric car braking
feedback
Lenz Lab
Changing Magnetic Flux Produces An Induced Electric Field
Copper Tube, NIB Magnet
Eddy Currents
1900: Free Electron Theory
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
Free Electron Theory Lab
Current electricity Electrons flow through a wire▪ Slow movement
Circuit needed Complete circuits using Alien Ball Turn on the light bulb
Turn on two light bulbs Create more advanced circuits▪ Parallel & series
1957: BCS Theory
BCS: Bardeen, Cooper, Schreiffer At low temperatures, some metals lose
resistance Atoms nearly stationary
Superconductivity results from the formation of Cooper pairs Two electrons partnered One follows the other
Results in frictionlessflow of electrons
BCS Lab
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
Additional ResourcesSTOP FAKING IT: ELECTRICITY & MAGNETISMBILL ROBERTSON
DRIVING FORCE: THE NATURAL MAGIC OF MAGNETSJAMES D. LIVINGSTON
Additional ResourcesA SHORT HISTORY OF NEARLY EVERYTHINGBILL BRYSON
THE NATURE OF SCIENCEJAMES TREFIL
Additional ResourcesHIDDEN ATTRACTION: THE MYSTERY & HISTORY OF MAGNETISMGERRIT L. VERSCHUUR
THE COLD WARS: A HISTORY OF SUPERCONDUCTIVITYJEAN MATRICON & GEORGES WAYSAND
Additional Resources
http://education.magnet.fsu.edu MagLab Alpha; Science, Optics, & You;
other curriculum MagLab audio slideshows
RET Program K-12 Programs MagLab Educator’s Club
Thank You
Carlos R. VillaNational High Magnetic Field [email protected] • 850-644-7191