MagnetismMagnetism

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BellworkBellwork

►Where is the Earth’s north Where is the Earth’s north magneticmagnetic pole located? pole located?

*Turn in the lab.*Turn in the lab.►Near the south geographic pole or Near the south geographic pole or

Antarctica.Antarctica.

BW Aside: Compass BW Aside: Compass HistoryHistory

►Invented Invented around 200 around 200 B.C. in ChinaB.C. in China

►Used Used loadstones to loadstones to align with the align with the Earth’s Earth’s Magnetic fieldMagnetic field

Today’s AgendaToday’s Agenda

►BellworkBellwork►Magnetism Pre-QuizMagnetism Pre-Quiz►Notes on MagnetismNotes on Magnetism►Homework: Magnetic FieldsHomework: Magnetic Fields

Due DatesDue Dates

►Tues. (4/1): Rough draft of the Tues. (4/1): Rough draft of the Science Fiction Story dueScience Fiction Story due

►Wed. (4/2): Magnetic Fields H.W. Wed. (4/2): Magnetic Fields H.W. duedue

►Tues. (4/8): Final draft of the Tues. (4/8): Final draft of the Science Fiction Story dueScience Fiction Story due

Pre-QuizPre-Quiz►1) Magnets can attract and repel 1) Magnets can attract and repel

certain materials.certain materials.►2) Magnets repel non metals.2) Magnets repel non metals.►3) Magnets will attract / repel all 3) Magnets will attract / repel all

metals. metals. ►4) Moving electrons are the 4) Moving electrons are the

source of magnetism.source of magnetism.►5) The larger the magnet the 5) The larger the magnet the

stronger the magnetic force.stronger the magnetic force.

Pre-QuizPre-Quiz►6) Magnetic fields are three 6) Magnetic fields are three

dimensional.dimensional.►7) Only magnets have magnetic 7) Only magnets have magnetic

fields.fields.►8) A magnet can have only one 8) A magnet can have only one

magnetic pole.magnetic pole.►9) Magnetism will be blocked by 9) Magnetism will be blocked by

materials that are insulators.materials that are insulators.►10) The magnetic north pole is 10) The magnetic north pole is

located near the geographical North located near the geographical North Pole.Pole.

Pre-Quiz AnswersPre-Quiz Answers►1) Magnets can attract and repel 1) Magnets can attract and repel

certain materials.certain materials.►TRUETRUE►2) Magnets repel non metals.2) Magnets repel non metals.►FALSEFALSE►3) Magnets will attract / repel all 3) Magnets will attract / repel all

metals.metals.►FALSEFALSE

Pre-Quiz AnswersPre-Quiz Answers►4) Moving electrons are the 4) Moving electrons are the

source of magnetism.source of magnetism.►TRUETRUE►5) The larger the magnet the 5) The larger the magnet the

stronger the magnetic force.stronger the magnetic force.►FALSEFALSE►6) Magnetic fields are three 6) Magnetic fields are three

dimensional.dimensional.►TRUETRUE

Pre-Quiz AnswersPre-Quiz Answers

►7) Only magnets have magnetic 7) Only magnets have magnetic fields.fields.

►FALSEFALSE►8) A magnet can have only one 8) A magnet can have only one

magnetic pole.magnetic pole.►FALSEFALSE

Pre-Quiz AnswersPre-Quiz Answers

►9) Magnetism will be blocked by 9) Magnetism will be blocked by materials that are insulators.materials that are insulators.

►FALSEFALSE►10) The magnetic north pole is 10) The magnetic north pole is

located near the geographical located near the geographical North Pole.North Pole.

►FALSEFALSE

Gravity vs. Electromagnetic Gravity vs. Electromagnetic ForceForce

►The Electromagnetic force is 10The Electromagnetic force is 102020 time stronger then gravity!time stronger then gravity!

MagnetismMagnetism► Opposite poles Opposite poles

attractattract► Like poles repelLike poles repel► Magnetic poles Magnetic poles

ALWAYSALWAYS come in come in pairspairs

► Magnetic fields Magnetic fields are produced by are produced by the the motionmotion of an of an electric chargeelectric charge

Magnetic FieldsMagnetic Fields

Magnetic Field LinesMagnetic Field Lines

►Start at the north pole and end on Start at the north pole and end on the south polethe south pole

Atomic Level of MagnetismAtomic Level of Magnetism(source of magnetism)(source of magnetism)

► Electrons spin about their axisElectrons spin about their axis► Electrons orbit around the nucleusElectrons orbit around the nucleus

Magnetic MaterialsMagnetic Materials

►IronIron►NickelNickel►CobaltCobalt- These are the only three These are the only three

elements that the electron’s spin elements that the electron’s spin and orbit align with each otherand orbit align with each other

- Other elements’ spins and Other elements’ spins and orbits cancel outorbits cancel out

Magnetic DomainsMagnetic Domains

► Magnetic Domain:Magnetic Domain: A microscopic A microscopic cluster of atoms cluster of atoms with their magnetic with their magnetic fields alignedfields aligned

► Heating or Heating or dropping a magnet dropping a magnet will weaken it will weaken it (causing the (causing the domains to become domains to become unaligned)unaligned)

Breaking a MagnetBreaking a Magnet

► If you break a If you break a magnet in half magnet in half you end up with you end up with two smaller two smaller magnetsmagnets

► Even all the way Even all the way down to the down to the atomic levelatomic level

Right Hand RuleRight Hand Rule

►Right-Hand Rule:Right-Hand Rule: determines the determines the direction of the magnetic field direction of the magnetic field around a current-carrying wire around a current-carrying wire   

Right Hand RuleRight Hand Rule

► Point your thumb Point your thumb in the direction of in the direction of the current (I)the current (I)

► The curl of your The curl of your fingers shows the fingers shows the direction of the direction of the magnetic field (B)magnetic field (B)

                                   

Right Hand Rule Symbols

• Vector arrows and loops

• A dot “●” means out of the page

• An ex “X” means into the page

• Label the symbols I = currentB = magnetic field

• Dots “●” and exes “X” must be in pairs!