MAGNETISMMAGNETISM

MAGNETISM –THE ABILITY OF CERTAIN MAGNETISM –THE ABILITY OF CERTAIN MATERIALS TO ATTRACT IRON, COBALT MATERIALS TO ATTRACT IRON, COBALT

OR NICKEL.OR NICKEL.

CLASSIFICATION OF MAGNETSCLASSIFICATION OF MAGNETS

NATURAL MAGNETSNATURAL MAGNETS ARTIFICIAL PERMANENT MAGNETSARTIFICIAL PERMANENT MAGNETS ELECTROMAGNETELECTROMAGNET

NATURAL MAGNET -EARTHNATURAL MAGNET -EARTH

NATURAL MAGNETS--NATURAL MAGNETS--LODESTONESLODESTONES

LODESTONES BECAME LODESTONES BECAME MAGNETIZED BY LYING IN MAGNETIZED BY LYING IN THE EARTH’S MAGNETIC THE EARTH’S MAGNETIC

FIELD FOR THOUSANDS OF FIELD FOR THOUSANDS OF YEARSYEARS

THE ANCIENT GREEKS RECOGNIZED THE ANCIENT GREEKS RECOGNIZED THE MAGNETISM OF LODESTONES THE MAGNETISM OF LODESTONES

MORE THAN 2500 YEARS AGOMORE THAN 2500 YEARS AGO

THE SPHERE OF ARCHIMEDES

ARTIFICIAL PERMANENT ARTIFICIAL PERMANENT MAGNETSMAGNETS

HARD STEEL HARD STEEL MAGNETIC COMPASSMAGNETIC COMPASS ALNICOALNICO

HARD STEEL—HORSHOE HARD STEEL—HORSHOE MAGNETMAGNET

MAGNETIC COMPASSMAGNETIC COMPASS

The magnetic compass was brought to Europe in the Middle Ages from the Chinese who had been using the compass for over 1500 years

ALNICO—ALLOY OF: ALNICO—ALLOY OF:

AL—ALUMINIUMAL—ALUMINIUM

NI—NICKELNI—NICKEL

CO—COBALTCO—COBALT

ALUMINUM CAN NOT BE ALUMINUM CAN NOT BE MAGNETIZEDMAGNETIZED

ALNICO—SUPER STRONG ALNICO—SUPER STRONG MAGNETSMAGNETS

ELECTROMAGNETS ELECTROMAGNETS TEMPORARY MAGNETS TEMPORARY MAGNETS

PRODUCED BY MEANS OF PRODUCED BY MEANS OF ELECTRIC CURRENT. ELECTRIC CURRENT.

ELECTROMAGNETELECTROMAGNET

MRI ELECTROMAGNETMRI ELECTROMAGNET

LAWS OF MAGNETISMLAWS OF MAGNETISM

EVERY MAGNET HAS TWO POLES EVERY MAGNET HAS TWO POLES LIKE MAGNETIC POLES REPEL: LIKE MAGNETIC POLES REPEL:

UNLIKE POLES ATTRACTUNLIKE POLES ATTRACT THE FORCE OF ATTRACTION OR THE FORCE OF ATTRACTION OR

REPULSION FOLLOWS INVERSE REPULSION FOLLOWS INVERSE SQUARE LAW ( NOT ACCURATE)SQUARE LAW ( NOT ACCURATE)

EVERY MAGNET HAS TWO EVERY MAGNET HAS TWO POLES-POLES-

NORTH & SOUTHNORTH & SOUTH

LIKE MAGNETIC POLES REPELEACH LIKE MAGNETIC POLES REPELEACH OTHEROTHER

UNLIKE POLES ATTRACT EACH OTHERUNLIKE POLES ATTRACT EACH OTHER

THE FORCE OF ATTRACTION THE FORCE OF ATTRACTION OR REPULSION BETWEEN OR REPULSION BETWEEN

TWO MAGNETSTWO MAGNETS

THE FORCE IS PROPORTIONAL TO THE THE FORCE IS PROPORTIONAL TO THE PRODUCT OF THE MAGNETIC POLE PRODUCT OF THE MAGNETIC POLE

STRENGTHS DIVIDED BY THE SQUARE STRENGTHS DIVIDED BY THE SQUARE OF THE DISTANCE BETWEEN THEM OF THE DISTANCE BETWEEN THEM

PpF = k

d2

NATURE OF MAGNETISMNATURE OF MAGNETISM

BREAKING A MAGNET WILL RESULT IN BREAKING A MAGNET WILL RESULT IN EACH FRAGMENT BECOMING A WHOLE EACH FRAGMENT BECOMING A WHOLE

MAGNETMAGNET

HEATING OR HAMERING STEEL IN HEATING OR HAMERING STEEL IN PROXIMITY TO A MAGNET –WILL PROXIMITY TO A MAGNET –WILL MAGNETIZE IT.MAGNETIZE IT.

STROKING OF IRON WITH MAGNET STROKING OF IRON WITH MAGNET WILL MAGNETIZE ITWILL MAGNETIZE IT

GENTLY JARRING A TEST TUBE OF GENTLY JARRING A TEST TUBE OF IRON FILINGS NEAR A MAGNET WILL IRON FILINGS NEAR A MAGNET WILL MAGNETIZE ITMAGNETIZE IT

MAGNETIZATIONMAGNETIZATION

AN ELECTRIC CHARGE AN ELECTRIC CHARGE SPINNING ON ITS AXIS WILL SPINNING ON ITS AXIS WILL CREATE MAGNETIC FIELDCREATE MAGNETIC FIELD

MOVING CHARGED PARTICLE MOVING CHARGED PARTICLE WILL INDUCE MAGNETIC WILL INDUCE MAGNETIC

FIELD FIELD

THE SMALL MAGNET THE SMALL MAGNET CREATED BY ELECTRON CREATED BY ELECTRON

ORBIT IS CALLED A ORBIT IS CALLED A MAGNETIC DIPOLEMAGNETIC DIPOLE

ACCUMULATION OF MANY ATOMIC ACCUMULATION OF MANY ATOMIC MAGNETS WITH THEIR DIPOLES MAGNETS WITH THEIR DIPOLES ALIGNED CREATES A MAGNETIC ALIGNED CREATES A MAGNETIC

DOMAINDOMAIN

THE MAGNETIC DIPOLES IN THE MAGNETIC DIPOLES IN BAR MAGNET GENERATE BAR MAGNET GENERATE IMAGINARY LINES OF THE IMAGINARY LINES OF THE

MAGNETIC FIELDMAGNETIC FIELD

MAGNETIC LINES OF FORCE MAGNETIC LINES OF FORCE ARE CLOSE LOOPSARE CLOSE LOOPS

MAGNETIC LINES OF FORCEMAGNETIC LINES OF FORCEEARTHEARTH

MAGNETIC LINES OF FORCEMAGNETIC LINES OF FORCEBAR MAGNETBAR MAGNET

THE STRENGTH OF THE STRENGTH OF MAGNETIC FIELD IS MAGNETIC FIELD IS

EXPRESSED IN SI UNIT EXPRESSED IN SI UNIT TESLATESLA

1 TESLA = 10,000 GAUSSES

MAGNETIC ELEMENT TWO MAGNETIC ELEMENT TWO OR MORE ELECTRONS OR MORE ELECTRONS SPINNING IN THE SAME SPINNING IN THE SAME

DIRECTIONDIRECTION

NUCLEUS

A MAGNETIC ELEMENT CAN A MAGNETIC ELEMENT CAN EXISTS EITHER IN EXISTS EITHER IN

MAGNETIZED OR NON-MAGNETIZED OR NON-MAGNETIZED STATE MAGNETIZED STATE

MAGNETIZED MAGNETIC MAGNETIZED MAGNETIC MATERIALMATERIAL

NON-MAGNETIZED MAGNETIC NON-MAGNETIZED MAGNETIC MATERIALMATERIAL

IN NONMAGNETIC MATERIALS JUST AS IN NONMAGNETIC MATERIALS JUST AS MANY ELECTRONS SPIN IN ONE MANY ELECTRONS SPIN IN ONE

DIRECTION AS IN OTHER.DIRECTION AS IN OTHER.THEIR OPPOSING MAGNETIC FIELDS THEIR OPPOSING MAGNETIC FIELDS

CANCEL OUTCANCEL OUT

NUCLEUS

AURORA BOREALISAURORA BOREALIS

CHARACTERISTICS OF THE CHARACTERISTICS OF THE LINES OF FORCELINES OF FORCE

FROM NORTH TO SOUTH OUSIDE THE FROM NORTH TO SOUTH OUSIDE THE MAGNET IN THE SPACEMAGNET IN THE SPACE

FROM SOUTH TO NORTH INSIDE THE FROM SOUTH TO NORTH INSIDE THE MAGNETMAGNET

IF IN THE SAME DIRECTION THEY WILL IF IN THE SAME DIRECTION THEY WILL REPELREPEL

MAGNETIC FIELD IS DISTORTED BY MAGNETIC FIELD IS DISTORTED BY MAGNETIC MATERIALS BUT NOT AFFECTED MAGNETIC MATERIALS BUT NOT AFFECTED BY NON-MAGNETIC MATERIALSBY NON-MAGNETIC MATERIALS

LINES OF FORCELINES OF FORCE

LINES OF FORCELINES OF FORCE

N S

N S

REPEL

LINES OF FORCELINES OF FORCE

N S

S N

ATTRACT

NONMAGNETIC MATERIALS DO NONMAGNETIC MATERIALS DO NOT AFFECT THE LINES OF NOT AFFECT THE LINES OF FORCE OF MAGNETIC FIELDFORCE OF MAGNETIC FIELD

MAGNETIC MATERIALS LIKE MAGNETIC MATERIALS LIKE IRON AFFECT THE LINES OF IRON AFFECT THE LINES OF

FORCEFORCE

MAGNETIC INDUCTION MAGNETIC INDUCTION (MAGNETIZATION)(MAGNETIZATION)

MAGNETIZATION –DOMAINS MAGNETIZATION –DOMAINS MOVEMOVE

MAGNETIC MAGNETIC PERMEABILITYPERMEABILITY

EASE WITH WHICH A GIVEN EASE WITH WHICH A GIVEN MATERIAL CAN BE MATERIAL CAN BE

MAGNETIZEDMAGNETIZED

MAGNETIC MAGNETIC RETENTIVITYRETENTIVITY

MATERIAL RESISTANCE TO MATERIAL RESISTANCE TO MAGNETIZATIONMAGNETIZATION

SOFT IRON HIGH SOFT IRON HIGH PERMEABILITY LOW PERMEABILITY LOW

RETENTIVITYRETENTIVITY

HARD STEEL LOW HARD STEEL LOW PERMEABILITY HIGH PERMEABILITY HIGH

RETENTIVITYRETENTIVITY

““EASY COME—EASY GO”EASY COME—EASY GO”

MAGNETIC CLASSIFICATION OF MAGNETIC CLASSIFICATION OF MATTERMATTER

FERROMAGNETICFERROMAGNETIC

PARAMAGNETIC MATERIALSPARAMAGNETIC MATERIALS

NONMAGNETIC MATERIALSNONMAGNETIC MATERIALS

DIAMAGNETIC MATERIALSDIAMAGNETIC MATERIALS

FERROMAGNETIC FERROMAGNETIC MATERIALS –IRON, MATERIALS –IRON, COBALT, NICKEL. COBALT, NICKEL.

STRONGLY ATTRACTED STRONGLY ATTRACTED BY MAGNETSBY MAGNETS

PARAMAGNETIC PARAMAGNETIC MATERIALS—PLATINUM. MATERIALS—PLATINUM. FEEBLY ATTRACTED BY FEEBLY ATTRACTED BY

MAGNETSMAGNETS

NONMAGNETIC NONMAGNETIC MATERIALS—COPPER, MATERIALS—COPPER,

WOOD, GLASS. THEY ARE WOOD, GLASS. THEY ARE NOT ATTRACTED TO NOT ATTRACTED TO

MAGNETS.MAGNETS.

DIAMAGNETIC DIAMAGNETIC MATERIALS—BERYLLIUM MATERIALS—BERYLLIUM

& BISMUTH. FEEBLY & BISMUTH. FEEBLY REPELLED BY MAGNETSREPELLED BY MAGNETS

DETECTION OF DETECTION OF MAGNETISM ---COMPASSMAGNETISM ---COMPASS

GEOGRAPHIC NORTH POLE IS GEOGRAPHIC NORTH POLE IS MAGNETIC SOUTH POLE?????MAGNETIC SOUTH POLE?????

S. GEOGRAPHIC

N. GEOGRAPHICS. MAGNETIC

N. MAGNETIC

SMALL MAGNETSSMALL MAGNETS