Magnetism Magnetism 3/28/14 3/28/14
Dec 15, 2015
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 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!