Are MAGNETIC Personalities
Always Attractive?
Robert A. Schill, Jr.
University of Nevada, Las Vegas
Dept. of Electrical and Computer Engineering
4505 Maryland Parkway; Box 454026
Las Vegas, NV 89154-4026
(702) 895-1526/4183 Lab: (702) 895-1430
FAX: (702) 895-4075
e-mail: schill@ee.unlv.edu
URL: http://www.ee.unlv.edu/~schill
Dangerous Equipment
z
PLEASE FOLLOW DIRECTIONS
y In some cases we will use high currents
y In other cases we will be using fire
y Unless directed DO NOT TOUCH
z
Some experiments may be performed at
home
y Always keep Mom or Dad informed on the
experiment you want to perform before you
conduct the experiment
z
Science is FUN when one is Careful
Robert A. Schill, Jr.
Lied Discovery Children's Museum, Las Vegas, NV
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What is a Magnetic Field?
Robert A. Schill, Jr.
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Early Philosophers - Webster’s World
Encyclopedia 1999
z
300 BC
y The Chinese Book of the Devil Valley Master refers to lodestone
lining up with the earth's magnetic field.
z
?? BC
y Discovery in the west that the lodestone attracts iron
z
270 AD
y Chinese use compass for locating south
z
1044 AD
y Chinese use compass for navigation
z
12 th Century
y Arab physicist - “We know that the magnet loves the lodestone, but
we do not know whether the lodestone also loves the magnet or is
attracted to it against its will.”
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Experiment - Sewing Needle Compass
Robert A. Schill, Jr.
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LODESTONE
z
Natural magnetic iron
ore called magnetite
z
First known magnet.
z
Iron filings are
attached to this stone
z
Iron oxide (rust) is
seen on the right of
the lodestone
Beulah Junior School Class 5P, Minerals, Crystals and their Properties,
National Science, Engineering and Technology Week 13-22 March, 1998.
Robert A. Schill, Jr.
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More Recent Philosophers - Webster’s
World Encyclopedia 1999
z
1600 William Gilbert
z
1635
z
1749
1819
1821
1831
z
z
z
z
z
z
1832
1835
1845
z
1873
1966
z
1981
z
Clearly explains that the earth behaves like a magnet in
Gilbert’s De Magnete.
Henry Gellibrand Reports that compass north varies from year to year
in a given place, in a regular way.
John Canton
Develops a method for making an artificial magnet.
Hans Oersted
Magnetic current affects a compass needle
Michael Faraday Creates the first two electrical motors.
Michael Faraday Discovers electromagnetic induction, discovered
earlier but not published by Joseph Henry.
Joseph Henry
Discovers transformer effect.
Michael Faraday Discovers self-induction, independently of Joseph Henry.
Michael Faraday
Discovers the Faraday effect: a magnetic field makes
the plane of polarized light rotate.
James C. Maxwell Influenced (among other things) by Faraday.
various authors The earth's magnetic field is shown to reverse,
swapping north and south poles.
Blakemore & Frankel Discovery that bacteria have a magnetic sense.
Robert A. Schill, Jr.
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[6/22/99]
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BUT What is a Magnetic Field?
Robert A. Schill, Jr.
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Role Play
z
z
Collisional force - Billiard Ball Force
Force at a Distance
Robert A. Schill, Jr.
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Philosophical Question - Has no REAL
answer!
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z
z
z
We only experience the force created by the
magnetic field.
Philosophers/Scientists needed a way to make
a connection between the object creating the
force and the object experiencing the force.
They devised (dreamed up)
up a mechanism or
model to describe FORCE AT A DISTANCE.
The magnetic field line was the mechanism
which allows one to visualize a “force field”
touching the object feeling the force.
Robert A. Schill, Jr.
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How is a Magnetic Field Generated?
z
Magnetic Field Generated
y By moving charge
y By current (which is a moving
charge)
z
Like the very early Chinese,
we will use a compass to
examine the direction of the
magnetic field.
z
Experiment - Current Generated
Magnetic Field
Robert A. Schill, Jr.
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Orientation of Magnetic Field
I
B
z
Right Hand Rule
z
y Place thumb of right hand in
the direction of current
y Fingers on right hand curl in the
direction of the magnetic field
Robert A. Schill, Jr.
z
Valid for Long Straight
Wire
Useful for Guessing at
Field Orientation
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Force Acting on Parallel Wires
Containing a Current
z Experiment - Force Between
Wire
Wire
Currents
2
1
z
F1
I2
I1
B2
F2
X
F1
Observations
y Direction of magnetic field
generated by wire 1 at wire 2
y Direction of current in wire 2
y Direction of the force on wire
2
y What about wire 1? Does it
move too? Which direction?
Is this reasonable? Why?
B1
.
Can we relate this to a
F2
Right-Hand-Rule?
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Robert A. Schill, Jr.
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Wire
1
Direction of Magnetic Force
Wire
2
F1
I2
I1
B2
I; Direction of Current at P
z
B; Direction
of Magnetic
Field at P
Direction of
Force at Point P
Robert A. Schill, Jr.
P
F2
X
.
F1
Right Hand Rule
F2
for Force at P due to I & B
y Point straightened fingers on
right hand in the direction of
the current at point P
y Bend fingers in the direction
of magnetic field at point P
y Thumb on right hand points
in direction of force
experienced at P
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B1
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If We Need A Current To Generate a
Magnetic Field, Then How Do Magnets
Work?
z
z
z
Magnets do not require
batteries to work!
Material Effect
Electrons Exhibit
y Orbital Motion
y Spin Motion
Robert A. Schill, Jr.
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Model for Magnetic Materials - 1
z
z
z
Imagine that Magnetic Material
consist of many atomic current
loops - (dipole moments, m)
Originally in the absence of a
magnetic field, the current
loops are randomly oriented.
In presence of a magnetic field,
the current loops align in such
a manner that the tiny
magnetic fields, m, of each
loop adds to that of the
external field, B.
Electromagnetics by John D. Kraus, 4th edition, 1992.
Robert A. Schill, Jr.
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Model for Magnetic Materials - 2
N
S
Electromagnetics by John D. Kraus, 4th edition, 1992.
z
Tiny atomic current loops
cancel inside material if
atomic loops are uniform
Robert A. Schill, Jr.
z
Yields a large loop current
on outside of magnet due to
atomic loop currents
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Permanent Magnet vs Electromagnet
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Permanent Magnet - Experiment Field Lines in 3-D Using Iron Filings
y Does not require an external current
y Material is hard to demagnetize
(ceramic & aluminum-nickel-cobalt
alloy (alnico))
z
Electromagnet - Experiment - Build
Electromagnet
y Magnetic field generated by an
external current usually in the shape of
a coil (solenoid) wrapped around a
magnetic material (iron)
y When current is turned off, easy to
demagnetize.
Robert A. Schill, Jr.
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Some Flavors of Magnetic Materials
z
z
Diamagnetic - weakly repels
applied magnetic field; orbital
motion of electron dominates
(Reverse Magnet - levitates)
(Bismuth, Cu, H2O, gold)
(Faraday 1846)
Ferromagnetic - strongly
attracted by a magnetic field;
electron spin align within each
section (domain) of the
material (iron, cobalt, nickel)
Robert A. Schill, Jr.
z
Paramagnetic - weakly
attracted by a magnetic
field; orbit and spin magnetic
moments compete. The
magnetic moments align with
the applied field causing the
total field to be slightly
increased. At high enough
temperatures, all strong
magnetic materials
become paramagnetic.
Experiment - Demagnetizing
(aluminum, potassium)
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Is the Earth’s Magnetic Field Important?
N
S
NGDC - National Geophysical Data Center
z
z
z
The earth’s magnetic field shields the earth
from harmful cosmic radiation.
The earth’s field acts as a magnetic bottle. Ions
are trapped in the atmosphere. Low frequency
radio waves bounce off of these ions to other
parts of the world.
Appears to have a biological significance
Robert A. Schill, Jr.
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How Solar Wind Affects the Earth’s
Magnetic Field and Its Consequences.
Electromagnetics by John D. Kraus, 4th edition, 1992.
Robert A. Schill, Jr.
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The Auroras
Borealis Goddess of Dawn
in the North
Geo Data Center from the
University of Alaska Fairbanks
3 Luminous bands or
streamers of light that are
sometimes visible in the
night skies of northern
regions. They are caused
by the ejection of charged
particles into the magnetic
field of the earth. (Northern
lights).
Robert A. Schill, Jr.
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About a 10% Decline in the Earth’s
Magnetic Field Over a 100 Year Period
1900
2000
National Geophysical Data Center
z
z
z
z
Magnetic (North/South) pole reversal are common
Occurs about once every half a million years or so
Currently unable to predict next pole reversal
Last field reversal occurred about 700,000 years
ago
Robert A. Schill, Jr.
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[6/22/99]
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Do Magnetic Fields Affect Animals and
People?
z
z
Bioelectromagnetism
Living things
y
y
y
y
y
y
Astronauts
Pigeons
Salamanders
Tadpoles
Honey bee
Bacteria
Robert A. Schill, Jr.
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Salamanders Fall Asleep (Anesthetized) in
Large Magnetic Field
z
The Body Electric Electromagnetism and the
Foundation of Life, R.O. Becker and G. Selden,
Morrow Publications, 1985.
Robert A. Schill, Jr.
Robert Becker (1963)
y At 3,000 G the animal was
motionless and unresponsive
to all stimuli - EEG
(electroencephalogram)
showed simple delta brain
waves
y Decreasing the magnetic field
the animal recovered within
seconds - Normal EEG
y No apparent side effects
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Cosmonauts (Soviet Astronauts),
Pigeons, Honeybees, and Bacteria
z
z
Honing Pigeons - navigated by earth’s magnetic
field even when sun is shining
Early cosmonauts experienced bone-calcium loss
and muscle cramps in space above the earth’s
magnetic for an extended amount of time.
y Health maintained when artificial magnetic
fields were placed in space capsule
z
z
Honey bees disoriented in large magnetic fields
Freshwater Bacteria cultured in an iron rich
medium travel either North or South
y Contain magnetite like particles
Robert A. Schill, Jr.
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UNLV Research: Interaction of DC & 60 Hz
Magnetic Fields With Tadpoles
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UNLV Research - Dr. Karin Hoff and
Dr. Robert Schill, Jr.
y Designed and built magnetic coils
x Solenoid Coil
x Helmholtz Coil
z
z
z
Robert A. Schill, Jr.
Respond?
How?
Why?
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Exp. Set-up and Tentative Conclusions
y Body posture of tadpole is
sensitive to magnetic field
y Tadpoles feel presence of
small magnetic fields - less
than 1/7 of earth’s field
x Earth’s magnetic field - 0.5 G
x Hair Dryer - 0.3 G at 6”
x Vacuum Cleaner 0.06 G at 1’
x Analog Clock 0.015 G at 1’
Eye
Tadpole
Robert A. Schill, Jr.
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Film Clip & Current Research Goal
z
What Health
Benefits Exist?
y Mechanism?
z
Film Clip
y 0-30 min Field Off
y 30-60 min; 0.07 G
60 Hz Field On
Dr. Hoff & Schill’s Research
June 1999.
Robert A. Schill, Jr.
Picture from:
This Week in Green Valley Paper
Nov. 21, 1997.
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Some Interesting Applications of
Magnetic Fields
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z
z
Ore Separation
Magnetic Levitation (MAGLEV) Vehicles
Pulse Power Nuclear Fusion
Robert A. Schill, Jr.
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Ore Separation
z
z
z
z
Robert A. Schill, Jr.
Electromagnetic is
typically used
At Room
Temperature, the only
materials with strong
magnetic properties
are Iron, Cobalt, and
Nickel Alloys
Aluminum, Copper,
etc.: NOT magnetic.
Would you touch
that?
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MAGLEV vs Other Forms Transportation
z
z
A fast, inexpensive means of transportation is
crucial in today’s business and society.
Typical Travel Speeds for Various Modes of
Transportation
y
y
y
y
y
z
z
Walking - 2 mph roughly (~ 15 to 20 miles per day)
Horse - roughly 30 miles per day comfortably
Car - 55 to 70 mph
Plane - 360 mph on average
MAGLEV - 250 to 300+ mph in near future
~ 1/3 Travel Energy Cost of a conventional plane
Green Transportation Technology - minimal air
and noise pollution
Robert A. Schill, Jr.
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How MAGLEV Vehicles Float
The EPRI Journal:
Jan./Feb. 1997
Vol. 22, No. 1.
y Electrodynamic, repulsion-type --American/Japan
x Levitation magnets on top of a guide rail
x Superconducting magnets on bottom side of vehicle (15 cm air gap)
y Electromagnetic, attraction-type -- German
x Conventional iron-core magnets on the vehicle
x Attracting magnets under the guide rail (1cm air gap)
Robert A. Schill, Jr.
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Different MAGLEV Designs
Swissmetro Project
The EPRI Journal: January/February 1997 Vol. 22, Number 1.
Robert A. Schill, Jr.
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Fusion Process
G. Yonas, Fusion and the Z Pinch, Scientific American, Aug. 1998.
z
z
z
Forcing together Deuterium and Tritium nuclei
Fuse into a form of Helium
Emits large amount of energy
Robert A. Schill, Jr.
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Pulse Power Fusion Process
z
G. Yonas, Fusion and the Z Pinch, Scientific American, Aug. 1998.
Robert A. Schill, Jr.
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A Successful Mechanism Leading to
Pulsed Power Fusion - Z Pinch
JxB
B
Rigid Return
Conductor
I
I
r
B
rc
I
Plasma
JxB
Plasma
Z-Pinch Mechanism
Robert A. Schill, Jr.
Z-Pinch Coaxial Geometry
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Building a Wire Array - Close-Up View
z
Wire Array - Single/Double
y ~1/10 th Dia. human hair
y 0.7 microns thick
y Array dia. ~ shot glass
z
Wire Material
y Al, Ti, Cu, W (Tungsten)
The pictures on this slide and the next three or four slides are from
Sandia National Laboratory in Albuquerque, New Mexico.
Robert A. Schill, Jr.
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Cartoon Picture of PBFA-Z or Z
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PBFA-Z or Z
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ARCS AND SPARKS: OPEN SHUTTER PICTURE Z
Robert A. Schill, Jr.
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Time Varying Fields
z
z
z
Robert A. Schill, Jr.
Static (Non time varying)
models begin to loose their
meaning as the fields
change slowly from a
constant state to a time
varying state.
Electric and Magnetic fields
are linked together - are one
The greater the fields
with time, the stronger the
link.
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What Does This Link Mean?
B-Field
E-Field
z
z
z
The Electric Field and
the Magnetic Field
feed off of each other.
The Electric and
Magnetic fields
circulate or link with
each other.
This is the key to
understanding how
light and radio waves
propagate through
space (radiation) without a source on.
Robert A. Schill, Jr.
z
z
E-Field
This implies that a time varying
magnetic field may generate
(induce) a voltage in a circuit. A
time varying electric field may
generate (induce) a current in a
circuit.
Recall in Static theory
y Magnetic fields were linked only to
current
y Electric fields are linked only to
voltages (potential differences)
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How Do The Fields Change?
Role Play
z
z
z
Nature resists change.
Induced voltages and currents are generated
in such a manner that it supports the field that
was present a moment ago.
Real quantities take time to change. Einstein
said that nothing can travel faster than the
speed of light. This statement of causality
implies that the chicken can never come
before the egg.
Robert A. Schill, Jr.
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Transformer Action - Magnetic Field Varies
with Time and Medium is Stationary
Experiment - Underwater Light
z A time varying magnetic field
B1(t) Decreasing with tgenerates (induces) a voltage
in a second coil which in turn
Coil 2
Light
drives a current to light the
I2
Bulb
light bulb.
z The time varying magnetic
field may be thought of as the
voltage source (electromotive
I1
v(t)
force) for the second circuit.
Coil 1
z
Robert A. Schill, Jr.
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z
Direction of
Motion
B
B
I
+
Motional Action Magnetic Field
Constant and
Medium Moves
-
Direction of
Motion
Experiment - Electromagnetic Catapult &
Electromagnetic Brake
z
z
z
The number of magnetic field lines enclosed by
the circuit changes. A current is generated in the
circuit to oppose this change.
The moving circuit may be thought of as being
the voltage source for the circuit.
If a physical battery is placed in the circuit, the
moveable rod will exhibit motion.
Robert A. Schill, Jr.
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Robert A. Schill, Jr.
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