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Magnetism Magnetism Physics Physics La Ca La Ca ñ ñ ada High School ada High School Dr.E Dr.E

Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

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Page 1: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

MagnetismMagnetismPhysicsPhysics

La CaLa Caññada High Schoolada High School

Dr.EDr.E

Page 2: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

MagnetismMagnetism11

• Magnetism is a force that attracts certain Magnetism is a force that attracts certain metalsmetals

• Magnets have two poles that act both Magnets have two poles that act both similarly and differently than electrical similarly and differently than electrical charges actcharges act

• Easy to detect magnetism, although it is not Easy to detect magnetism, although it is not easy to measure its strengtheasy to measure its strength

• Make a magnet by rubbing steel against Make a magnet by rubbing steel against another magnetanother magnet

Page 3: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Properties of MagnetismProperties of Magnetism• Magnetism is a force that attracts iron, Magnetism is a force that attracts iron,

nickel and cobaltnickel and cobalt• Combinations of these metals as alloys can Combinations of these metals as alloys can

become permanent sources of magnetismbecome permanent sources of magnetism• A lodestone is the naturally occurring A lodestone is the naturally occurring

magnetite that has the chemical formula magnetite that has the chemical formula Fe3O4

Page 4: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Magnetism is SafeMagnetism is Safe• Electrical charges can give a person a shock Electrical charges can give a person a shock

or even kill the personor even kill the person

• Magnetism doesn't seem to have any Magnetism doesn't seem to have any harmful effectsharmful effects

• People who claim that magnets are even People who claim that magnets are even beneficial to your healthbeneficial to your health

• Some companies sell magnetic Some companies sell magnetic materials that attach to your body materials that attach to your body to help relieve chronic pain. to help relieve chronic pain.

Page 5: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Magnets Attract IronMagnets Attract Iron• A magnet A magnet

– an object made of a material that attracts iron, an object made of a material that attracts iron, nickel and cobalt, as well as alloys of these nickel and cobalt, as well as alloys of these metalsmetals

– both attracts and repels other magnets. both attracts and repels other magnets.

• Magnetic force attracts and repels acts at a Magnetic force attracts and repels acts at a distance distance

• A few rare-earth materials such as bismuth A few rare-earth materials such as bismuth are actually repelled by a magnetare actually repelled by a magnet

Page 6: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Magnet has Two PolesMagnet has Two Poles• Opposite ends of a magnet are called its Opposite ends of a magnet are called its

north and south polesnorth and south poles– should be called the "north seeking" and should be called the "north seeking" and

"south seeking" poles, because they seek "south seeking" poles, because they seek the Earth's North Pole and South Pole, the Earth's North Pole and South Pole, respectivelyrespectively

• Like poles repelLike poles repel– north pole of magnet will push the north north pole of magnet will push the north

pole of another magnetpole of another magnet

Page 8: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Magnetic Field NatureMagnetic Field Nature• Magnetism originates Magnetism originates

in the motion of the in the motion of the electronselectrons

• Spinning electrons act Spinning electrons act like tiny magnetslike tiny magnets

• Cancellation of this Cancellation of this effect occurs in most effect occurs in most materialsmaterials

• Iron, nickel, cobalt are Iron, nickel, cobalt are exceptionsexceptions

Page 9: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Magnet – Electrical DifferenceMagnet – Electrical Difference

• Every magnet has a Every magnet has a north pole and a north pole and a south polesouth pole

• A magnet always A magnet always has a N and S polehas a N and S pole– If you cut a magnet If you cut a magnet

in half, each piece in half, each piece will still have a N will still have a N and S poleand S pole

Page 10: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Magnetic DomainsMagnetic Domains• The magnetic north-The magnetic north-

south axes of groups south axes of groups of iron atoms line up of iron atoms line up in the same directionin the same direction– Magnetic domainsMagnetic domains

• Domains are Domains are randomly oriented randomly oriented unmagnetized ironunmagnetized iron

Page 12: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

MagnetizationMagnetization

• An external magnetic field will twist An external magnetic field will twist the domains into alignmentthe domains into alignment– Domains are randomly oriented in Domains are randomly oriented in

unmagnetizedunmagnetized iron iron

– Incomplete alignment of domains in Incomplete alignment of domains in slightly magnetizedslightly magnetized iron iron

– Virtually all of the domains are aligned in Virtually all of the domains are aligned in strongly magnetizedstrongly magnetized iron iron

Page 13: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Detecting Magnetic FieldDetecting Magnetic Field• Iron filings on a Iron filings on a

piece of paper piece of paper – Spread fine iron Spread fine iron

filings on a piece of filings on a piece of paper laid on top of paper laid on top of a magneta magnet• Outline of the Outline of the

magnetic lines of magnetic lines of force or the force or the magnetic fieldmagnetic field

Page 14: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Detecting Magnetic FieldDetecting Magnetic Field• Compass Compass

– Thin magnet or Thin magnet or magnetized iron magnetized iron needle balanced on a needle balanced on a pivotpivot

– needle will rotate to needle will rotate to point toward the point toward the opposite pole of a opposite pole of a magnetmagnet

– One end marked N One end marked N and the other Sand the other S

Page 15: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

A Compass A Compass →→Magnetic FieldMagnetic Field

Page 16: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Measuring Magnetic Strength Measuring Magnetic Strength

• Not easy to measure Not easy to measure the strength of a the strength of a magnetic fieldmagnetic field

• Gauss meter is used Gauss meter is used to measure a to measure a magnetic fieldmagnetic field– meters uncommon meters uncommon

due to limited usedue to limited use

Page 17: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Electric Currents and Magnetic FieldElectric Currents and Magnetic Field

• Spinning or rotating Spinning or rotating electrons are electrons are responsible for responsible for magnetism in ironmagnetism in iron

• Moving charges set up Moving charges set up magnetic fieldsmagnetic fields

• Compasses (bar Compasses (bar magnets) line up in magnets) line up in circles around a wire circles around a wire carrying current.carrying current.

Page 18: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Iron Filings form Concentric Iron Filings form Concentric Circles around WireCircles around Wire

Page 19: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Electric Currents and Magnetic FieldElectric Currents and Magnetic Field33

• Magnetic field lines around a long wire Magnetic field lines around a long wire which carries an electric current form which carries an electric current form concentric circles around the wireconcentric circles around the wire

• The direction of the magnetic field is in The direction of the magnetic field is in the direction the fingers if your right the direction the fingers if your right hand curls around the wire with your hand curls around the wire with your thumb in the direction of the currentthumb in the direction of the current

Page 20: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Electric Currents and Magnetic FieldElectric Currents and Magnetic Field

Page 21: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Magnetic LevitationMagnetic Levitation• Trains float above guide Trains float above guide

way due to magnetic fieldway due to magnetic field

• Travel at speeds of up to Travel at speeds of up to 300 mph (500 kph)300 mph (500 kph)                                                                                           

Page 22: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Magnetic LevitationMagnetic Levitation

‘‘Superman the Superman the Ride’ works due Ride’ works due

to magnetic to magnetic levitationlevitation

Page 23: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Magnetic Forces on Moving Magnetic Forces on Moving Charged ParticlesCharged Particles

If charge particles move in a magnetic field, If charge particles move in a magnetic field, they experience a sideways forcethey experience a sideways force

Page 24: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Magnetic Forces on Current Magnetic Forces on Current Carrying WiresCarrying Wires

• Moving electrons in wire are pushed up, or Moving electrons in wire are pushed up, or down, depending on their directiondown, depending on their direction

Page 25: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Measuring CurrentsMeasuring Currents• Coils of current-carrying wires set up Coils of current-carrying wires set up

magnetic field perpendicular to plane of coilmagnetic field perpendicular to plane of coil

• Compass needle aligns itself with the field Compass needle aligns itself with the field lineslines

Page 26: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Current-Measuring ApparatusCurrent-Measuring Apparatus

• Electromagnet tends to Electromagnet tends to align its north face align its north face with the iron magnet's with the iron magnet's south facesouth face

• A spring resists this A spring resists this tendency to twist; the tendency to twist; the greater the current, the greater the current, the greater the deflection greater the deflection of the needleof the needle

Page 27: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Earth as a Earth as a Giant magnetGiant magnet• Earth's magnetic field is thought to be Earth's magnetic field is thought to be

generated deep inside the planetgenerated deep inside the planet

• An inner core of solid iron is surrounded by An inner core of solid iron is surrounded by an outer core of molten ironan outer core of molten iron

• They rotate at different rates, and the They rotate at different rates, and the interaction between the regions creates what interaction between the regions creates what scientists call a "hydromagnetic dynamo."scientists call a "hydromagnetic dynamo."

Page 28: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Earth’s Magnetosphere LayerEarth’s Magnetosphere Layer44

• Also named Van Allen Belts Also named Van Allen Belts • Protects the Earth from celestial bodies, Protects the Earth from celestial bodies,

harmful cosmic rays and particlesharmful cosmic rays and particles• Belts at thousands of kilometers above the Belts at thousands of kilometers above the

earth protect the living things on the Earth earth protect the living things on the Earth

from the fatal energy from the fatal energy that would otherwise that would otherwise

reach it from spacereach it from space

Page 29: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Earth’s Magnetic FieldEarth’s Magnetic Field55

• The Earth has a The Earth has a magnetic field with magnetic field with north and south polesnorth and south poles– reaches 36,000 miles reaches 36,000 miles

into space. into space. – surrounded in a surrounded in a

region called the region called the magnetospheremagnetosphere

– prevents most of the prevents most of the particles from the sun, particles from the sun, carried in solar wind, carried in solar wind, from hitting the Earthfrom hitting the Earth

Page 30: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

AuroraAurora• High Speed electrons

and protons from space travel along magnetic field lines

• Field lines are nearly horizontal near the equator which protects the atmosphere

• The field lines are nearly vertical at high latitude, thus the high speed particles can enter the atmosphere

Page 31: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain
Page 32: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain
Page 33: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Magnetic Pole LocationMagnetic Pole Location• Location of magnetic pole is not fixedLocation of magnetic pole is not fixed• Geographic north is called the Earth's Geographic north is called the Earth's

North Magnetic Pole by conventionNorth Magnetic Pole by convention• The North Magnetic Pole is actually the The North Magnetic Pole is actually the

south pole of the Earth's magnetic fieldsouth pole of the Earth's magnetic field– the north pole of a compass was defined the north pole of a compass was defined

as the pole that points to the geomagnetic as the pole that points to the geomagnetic northnorth

Page 34: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain
Page 35: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Earth’s Magnet FlipsEarth’s Magnet Flips• Magnetosphere can flip its orientation so that the Magnetosphere can flip its orientation so that the

field lines which were pointed toward the north field lines which were pointed toward the north pole change and point toward the south polepole change and point toward the south pole– record preserved in magnetic rocks which lie along record preserved in magnetic rocks which lie along

the ocean floorthe ocean floor

• Magnetism in these rocks points first in one Magnetism in these rocks points first in one direction, then in another direction, giving the direction, then in another direction, giving the ocean floor a stripped appearance (from a ocean floor a stripped appearance (from a magnetic point of viewmagnetic point of view– many times in the past the north pole has become the many times in the past the north pole has become the

south pole, and vice versasouth pole, and vice versa

Page 36: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain
Page 37: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

The Sun is The Sun is a Great Big a Great Big

MagnetMagnet

Page 38: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Sun’s Magnet FieldSun’s Magnet Field• The Sun is a big magnetThe Sun is a big magnet

• During solar minimum the Sun's magnetic During solar minimum the Sun's magnetic field resembles that of an iron bar magnet, field resembles that of an iron bar magnet, with great closed loops near the equator and with great closed loops near the equator and open field lines near the polesopen field lines near the poles

• The Sun's dipolar field is about as strong as The Sun's dipolar field is about as strong as a refrigerator magnet, or 50 gaussa refrigerator magnet, or 50 gauss

• Earth's magnetic field is 100 times weakerEarth's magnetic field is 100 times weaker

Page 39: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

SunspotsSunspots• Sunspots are places where intense magnetic Sunspots are places where intense magnetic

loops -- hundreds of times stronger than the loops -- hundreds of times stronger than the ambient dipole field -- poke through the ambient dipole field -- poke through the photospherephotosphere

• Sunspot magnetic fields overwhelm the Sunspot magnetic fields overwhelm the underlying dipoleunderlying dipole

• The Sun's magnetic field isn't confined to The Sun's magnetic field isn't confined to the immediate vicinity of our starthe immediate vicinity of our star

• The solar wind carries it throughout the The solar wind carries it throughout the solar systemsolar system

Page 40: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain
Page 41: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Magnetic Fields on the SunMagnetic Fields on the Sun

The Earth fits inside the loop

• Plasma, like iron Plasma, like iron filings, follows filings, follows magnetic field magnetic field lineslines

• Coronal loops Coronal loops created by hot, created by hot, glowing plasma glowing plasma flow along flow along magnetic field magnetic field lineslines

Page 42: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

Cell Phones and PagersCell Phones and Pagers• When there are many sun spots, it is called the When there are many sun spots, it is called the

solar maximumsolar maximum– lots of solar flares lots of solar flares – strong solar windstrong solar wind– radiation is also extra strongradiation is also extra strong

• All this solar activity can interfere with radio All this solar activity can interfere with radio waveswaves– cell phones and pagers don't work all the time cell phones and pagers don't work all the time – can hear solar static on car radio. can hear solar static on car radio.

Page 43: Magnetism Physics La Cañada High School Dr.E. Magnetism 1 1 Magnetism is a force that attracts certain metalsMagnetism is a force that attracts certain

BibliographyBibliography1.1. Magnetism information fromMagnetism information from School for Champions Website by Ron Kurtus (revised School for Champions Website by Ron Kurtus (revised

29 January 2002)29 January 2002) @ http://www.school-for-champions.com/science/magnetism.htm, @ http://www.school-for-champions.com/science/magnetism.htm, 4/15/044/15/04

2.2. Magnetism: Chapter 9Magnetism: Chapter 9 by by Joseph F. Alward, PhD, Department of Physics, University Joseph F. Alward, PhD, Department of Physics, University of the Pacificof the Pacific @ http://sol.sci.uop.edu/~jfalward/physics17/chapter9/chapter9.html @ http://sol.sci.uop.edu/~jfalward/physics17/chapter9/chapter9.html, , 4/15/044/15/04

3.3. HyperPhysicsHyperPhysics by Carl R. (Rod) Nave Department of Physics and Astronomy Georgia by Carl R. (Rod) Nave Department of Physics and Astronomy Georgia State UniversityState University @ http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magcur.html @ http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magcur.html, , 4/15/044/15/04

4.4. Creation of the UniverseCreation of the Universe The Qur’an and LifeThe Qur’an and Life by Harun Yahyaby Harun Yahya @ @ http://www.creationofuniverse.com/html/science_06.html , 4/15/04 http://www.creationofuniverse.com/html/science_06.html , 4/15/04

5.5. Earth’s Magnetic Field Earth’s Magnetic Field by Windows to the Universe, Last modified June 3, 2003by Windows to the Universe, Last modified June 3, 2003 @ @ http://www.windows.ucar.edu/tour/link=/earth/Magnetosphere/overview.html , http://www.windows.ucar.edu/tour/link=/earth/Magnetosphere/overview.html , 4/16/044/16/04

6.6. Windows to Universe Windows to Universe by Windows to the Universe, Last modified June 3, 2003by Windows to the Universe, Last modified June 3, 2003 @ @ http://www.windows.ucar.edu/spaceweather/location_mag_poles.html, 4/16/04http://www.windows.ucar.edu/spaceweather/location_mag_poles.html, 4/16/04

7.7. New clues to Earth's magnetic flip-flopsNew clues to Earth's magnetic flip-flops by CNN News, April 7, 2004by CNN News, April 7, 2004 @http://www.cnn.com/2004/TECH/space/04/07/poles.reverse/, 4/16/04@http://www.cnn.com/2004/TECH/space/04/07/poles.reverse/, 4/16/04