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 Laboratoryvilla@magnet.fsu.edu • 850-644-7191