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Are MAGNETIC Personalities Always Attractive?
Robert A. Schill, Jr.University of Nevada, Las Vegas
Dept. of Electrical and Computer Engineering4505 Maryland Parkway; Box 454026
Las Vegas, NV 89154-4026(702) 895-1526/4183 Lab: (702) 895-1430
FAX: (702) 895-4075e-mail: [email protected]
URL: http://www.ee.unlv.edu/~schill
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Dangerous Equipment
PLEASE FOLLOW DIRECTIONSIn some cases we will use high currentsIn other cases we will be using fireUnless directed DO NOT TOUCH
Some experiments may be performed at home
Always keep Mom or Dad informed on the experiment you want to perform before you conduct the experiment
Science is FUN when one is Careful
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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What is a Magnetic Field?
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Early Philosophers - Webster’s World Encyclopedia 1999
300 BCThe Chinese Book of the Devil Valley Master refers to lodestone lining up with the earth's magnetic field.
?? BCDiscovery in the west that the lodestone attracts iron
270 ADChinese use compass for locating south
1044 ADChinese use compass for navigation
12 th CenturyArab physicist - “We know that the magnet loves the lodestone, but we do not know whether the lodestone also loves the magnet or isattracted to it against its will.”
Experiment - Sewing Needle Compass
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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LODESTONE
Natural magnetic iron ore called magnetiteFirst known magnet. Iron filings are attached to this stoneIron 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. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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More Recent Philosophers - Webster’s World Encyclopedia 1999
1600 William Gilbert Clearly explains that the earth behaves like a magnet in Gilbert’s De Magnete.
1635 Henry Gellibrand Reports that compass north varies from year to year in a given place, in a regular way.
1749 John Canton Develops a method for making an artificial magnet.1819 Hans Oersted Magnetic current affects a compass needle 1821 Michael Faraday Creates the first two electrical motors.1831 Michael Faraday Discovers electromagnetic induction, discovered
earlier but not published by Joseph Henry.1832 Joseph Henry Discovers transformer effect.1835 Michael Faraday Discovers self-induction, independently of Joseph Henry.1845 Michael Faraday Discovers the Faraday effect: a magnetic field makes
the plane of polarized light rotate.1873 James C. Maxwell Influenced (among other things) by Faraday.1966 various authors The earth's magnetic field is shown to reverse,
swapping north and south poles.1981 Blakemore & Frankel Discovery that bacteria have a magnetic sense.
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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BUT BUT What is a Magnetic Field?
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Role PlayRole Play
Collisional force - Billiard Ball Force Force at a Distance
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Philosophical Question - Has no REALREALanswer!
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 updreamed 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. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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How is a Magnetic Field Generated?Magnetic Field Generated
By moving chargeBy current (which is a moving charge)
Like the very early Chinese, we will use a compass to examine the direction of the magnetic field.
Experiment - Current Generated Magnetic Field
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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I
B
Orientation of Magnetic Field
Right Hand RulePlace thumb of right hand in the direction of currentFingers on right hand curl in the direction of the magnetic field
Valid for Long Straight WireUseful for Guessing at Field Orientation
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Force Acting on Parallel Wires Containing a Current
Experiment - Force Between CurrentsObservations
Direction of magnetic field generated by wire 1 at wire 2Direction of current in wire 2Direction of the force on wire 2What about wire 1? Does it move too? Which direction? Is this reasonable? Why?
Can we relate this to a Right-Hand-Rule?
B2X F1
I1
F1
Wire1
.
F2
I2F2
Wire2
B1
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Direction of Magnetic Force
I; Direction of Current at P
B; Direction of Magnetic Field at P
Direction of Force at Point P
P
Right Hand Rule for Force at P due to I & B
Point straightened fingers on right hand in the direction of the current at point PBend fingers in the direction of magnetic field at point PThumb on right hand points in direction of force experienced at P
B2X F1
I1
F1
Wire1
.
F2
I2F2
Wire2
B1
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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If We Need A Current To Generate a Magnetic Field, Then How Do Magnets
Work?Magnets do not require batteries to work!Material EffectElectrons Exhibit
Orbital Motion
Spin Motion
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Model for Magnetic Materials - 1Imagine 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. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Model for Magnetic Materials - 2
Tiny atomic current loops cancel inside material if atomic loops are uniform
Yields a large loop current on outside of magnet due to atomic loop currents
NN
SS
Electromagnetics by John D. Kraus, 4th edition, 1992.
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Permanent Magnet vs ElectromagnetPermanent Magnet - Experiment -Field Lines in 3-D Using Iron Filings
Does not require an external currentMaterial is hard to demagnetize (ceramic & aluminum-nickel-cobalt alloy (alnico))
Electromagnet - Experiment - Build Electromagnet
Magnetic field generated by an external current usually in the shape of a coil (solenoid) wrapped around a magnetic material (iron)When current is turned off, easy to demagnetize.
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Some Flavors of Magnetic MaterialsDiamagnetic - weakly repelsapplied magnetic field; orbital motion of electron dominates (Reverse Magnet - levitates) (Bismuth, Cu, H2O, gold) (Faraday 1846)Ferromagnetic - stronglyattracted by a magnetic field; electron spin align within each section (domain) of the material (iron, cobalt, nickel)
Paramagnetic - weaklyattracted 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)
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Is the Earth’s Magnetic Field Important?
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
N
SNGDC - National Geophysical Data Center
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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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. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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The Auroras Borealis -
Goddess of Dawn in the North
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).
Geo Data Center from the University of Alaska Fairbanks
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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About a 10% Decline in the Earth’s Magnetic Field Over a 100 Year Period
Magnetic (North/South) pole reversal are commonOccurs about once every half a million years or soCurrently unable to predict next pole reversalLast field reversal occurred about 700,000 years ago
1900 2000National Geophysical Data Center
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Do Magnetic Fields Affect Animals and People?
BioelectromagnetismLiving things
AstronautsPigeonsSalamandersTadpolesHoney beeBacteria
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Salamanders Fall Asleep (Anesthetized) in Large Magnetic Field
Robert Becker (1963)At 3,000 G the animal was motionless and unresponsive to all stimuli - EEG (electroencephalogram) showed simple delta brain waves Decreasing the magnetic field the animal recovered within seconds - Normal EEGNo apparent side effects
The Body Electric Electromagnetism and theFoundation of Life, R.O. Becker and G. Selden,
Morrow Publications, 1985.
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Cosmonauts (Soviet Astronauts), Pigeons, Honeybees, and Bacteria
Honing Pigeons - navigated by earth’s magnetic field even when sun is shiningEarly cosmonauts experienced bone-calcium loss and muscle cramps in space above the earth’s magnetic for an extended amount of time.
Health maintained when artificial magnetic fields were placed in space capsule
Honey bees disoriented in large magnetic fieldsFreshwater Bacteria cultured in an iron rich medium travel either North or South
Contain magnetite like particles
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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UNLV Research: Interaction of DC & 60 Hz Magnetic Fields With Tadpoles
UNLV Research - Dr. Karin Hoff and Dr. Robert Schill, Jr.
Designed and built magnetic coilsSolenoid CoilHelmholtz Coil
Respond?How?Why?
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Exp. Set-up and Tentative ConclusionsBody posture of tadpole is sensitive to magnetic fieldTadpoles feel presence of small magnetic fields - less than 1/7 of earth’s field
Earth’s magnetic field - 0.5 GHair Dryer - 0.3 G at 6”Vacuum Cleaner 0.06 G at 1’Analog Clock 0.015 G at 1’
Tadpole
Eye
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Film Clip & Current Research GoalWhat Health Benefits Exist?
Mechanism?Film Clip
0-30 min Field Off30-60 min; 0.07 G 60 Hz Field On
Picture from: This Week in Green Valley PaperNov. 21, 1997.
Dr. Hoff & Schill’s ResearchJune 1999.
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Some Interesting Applications of Magnetic Fields
Ore SeparationMagnetic Levitation (MAGLEV) VehiclesPulse Power Nuclear Fusion
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Ore SeparationElectromagnetic is typically usedAt Room Temperature, the only materials with strong magnetic properties are Iron, Cobalt, and Nickel AlloysAluminum, Copper, etc.: NOT magnetic.Would you touch Would you touch that?that?
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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MAGLEV vs Other Forms TransportationA fast, inexpensive means of transportation is crucial in today’s business and society.Typical Travel Speeds for Various Modes of Transportation
Walking - 2 mph roughly (~ 15 to 20 miles per day)Horse - roughly 30 miles per day comfortablyCar - 55 to 70 mphPlane - 360 mph on averageMAGLEV - 250 to 300+ mph in near future
~ 1/3 Travel Energy Cost of a conventional planeGreen Transportation Technology - minimal air and noise pollution
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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How MAGLEV Vehicles Float
Electrodynamic, repulsion-type --American/JapanLevitation magnets on top of a guide railSuperconducting magnets on bottom side of vehicle (15 cm air gap)
Electromagnetic, attraction-type -- GermanConventional iron-core magnets on the vehicleAttracting magnets under the guide rail (1cm air gap)
The EPRI Journal:Jan./Feb. 1997Vol. 22, No. 1.
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Different MAGLEV Designs
Swissmetro Project
The EPRI Journal: January/February 1997 Vol. 22, Number 1.
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Fusion Process
Forcing together Deuterium and Tritium nucleiFuse into a form of HeliumEmits large amount of energy
G. Yonas, Fusion and the Z Pinch, Scientific American, Aug. 1998.
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Pulse Power Fusion Process
G. Yonas, Fusion and the Z Pinch, Scientific American, Aug. 1998.
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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A Successful Mechanism Leading to Pulsed Power Fusion - Z Pinch
J x B
B
I
Plasma
J x B
B
I
Ir
rc
Plasma
Rigid ReturnConductor
Z-Pinch Mechanism Z-Pinch Coaxial Geometry
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Building a Wire Array - Close-Up View
Wire Array - Single/Double~1/10 th Dia. human hair0.7 microns thickArray dia. ~ shot glass
Wire MaterialAl, Ti, Cu, W (Tungsten)
The pictures on this slide and the next three or four slides are fromSandia National Laboratory in Albuquerque, New Mexico.
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Cartoon Picture of PBFA-Z or Z
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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ARCS AND SPARKS: OPEN SHUTTER PICTURE Z
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Time Varying Fields
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 oneThe greater the fields with time, the stronger the link.
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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What Does This Link Mean?
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) with-out a source on.
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
Magnetic fields were linked only to currentElectric fields are linked only to voltages (potential differences)
E-FieldB-Field
E-Field
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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How Do The Fields Change?
Nature resists change.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.
Role PlayRole Play
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Transformer Action - Magnetic Field Varies with Time and Medium is Stationary
Experiment - Underwater LightA time varying magnetic field generates (induces) a voltage in a second coil which in turn drives a current to light the light bulb.The time varying magnetic field may be thought of as the voltage source (electromotive force) for the second circuit.
v(t)
LightBulb
B (t) Decreasing with t1
Coil 11I
2ICoil 2
Robert A. Schill, Jr. Lied Discovery Children's Museum, Las Vegas, NV [6/22/99]
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Motional Action -Magnetic Field Constant and
Medium MovesExperiment - Electromagnetic Catapult & Electromagnetic BrakeThe 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.
Direction ofMotion
Direction ofMotion
B
+
I
-
B