MAGNETISM

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MAGNETISM

• By Mr. Todd
• Notes provided by Mr. Martonik

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I. The Nature of Magnetism

• A.     What is Magnetism? 
• 1. Magnetism-a force of attraction or repulsion
  of magnetic materials due to an arrangement of
  electrons.
• 2.Loadstone is a rock that contains the mineral
  magnetite that attracted materials containing
  iron.

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• B.     What is a Magnetic Pole?
• 1.     A magnetic pole is an area of the magnet
  where the magnetic effect is the strongest.
• 2.     One pole of a magnet always points North.
  It is labeled the North Pole!

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• C.     What is a Magnetic Field? 
• 1.     A magnetic field is a region of magnetic
  force around the magnet.
• 2.     Magnet field lines spread from pole to
  pole (they curve). Arrows face toward the south
  pole.

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• 3.     Like poles repel unlike poles attract

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• 4. If a magnet breaks in two, you will have
• 2 smaller magnets with both poles.

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• D.     Inside a Magnet
• 1.     Electron Spin
•  
• a. The magnetic properties of a material depend
  on the structure of its atom.
• b. A moving electron produces a magnetic field
  it acts as if it is spinning as it orbits the
  nucleus.

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• 2.     Magnetic Domains
• A.      In most materials the magnetic fields of
  the atoms point in random directions and then
  cancel each other out.

ALUMINUM NAIL (PLASTIC, GLASS, ETC..)
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• B. In certain materials the magnetic fields
  of the spinning electrons are aligned with one
  another. This alignment is called magnetic
  domain.

IRON NAIL
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• 3.  Magnetic Materials
• A. Ferromagnetic material is a material that
  shows a strong magnetic effect
• (ex. Iron, Nickel, Cobalt).

IRON NAIL (BEFORE BEING PLACED IN A MAGNETIC
FIELD)
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•  E.     How Can You Make a Magnet?
• 1.     Take a ferromagnetic material and
• place it in a strong magnetic field or
  
• rub it with a strong magnet.
• 2.     Some may or may not keep their magnetism.
• 3. Magnetic domains all face the same direction

IRON NAIL (AFTER BEING PLACED IN A MAGNETIC
FIELD)
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• F.     How Can You Destroy or Break a Magnet?
• 1.     If a magnet is hit or drops, the domains
  will be knocked out of alignment.
• 2. Heating a magnet will destroy the magnetic
  field.

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• 3. A magnet that is broken in half will produce
  two smaller magnets. (The magnet will not be
  destroyed.)

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II. Electric Current and Magnetic Fields

• A. What is the Relationship Between and
  Electric Current and Magnetism?
• 1. In 1820 Danish Scientist Hans Christian
  Oersted saw that there was a relationship
  between magnets and electricity.

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• 2.   Electric current produces a magnetic field.
• 3.   Electricity flowing through a wire next to
  several compasses will cause the needles to
  align with the magnetic field produced.
• 4.  Atoms become magnetic because of moving
  electrons

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• B.     What are Conductors and Insulators?
• 1.   Conductors are materials where electrons
  move very freely (metals) (Electrons are loosely
  bound to their atoms).
• 2.      Insulators are materials where electrons
  do not move freely. (rubber, glass, sand,
  plastic) (Electrons are bound tight to their
  atoms).

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• C.     What is Electrical Resistance?
• 1.      A material that resists a flow of charges
  is
• called a resistor.
• 2. Electrons collide with a material (resistor).
  
• Heat energy as well as light energy can build
  up.
• 3. Tungsten- filament in a light bulb as a
  resistor.
• 4.  Super Conductors-a material which provides
• no electrical resistance (placed under low
  temps)

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III.   Electromagnets

• A.     What is a Solenoid?
• 1.      A solenoid is a current flowing through a
  wire creating a magnetic field around the wire.

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• 2.    Solenoid - a current carrying coil of wire
  with many loops. It creates a magnetic field
  which can be turned off or on with turning off or
  on the current.

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• B.     What is an Electromagnet?
• 1.      Electromagnet - a ferromagnetic material
  (iron) placed inside a solenoid. It produces a
  strong magnetic field.
• It is a strong magnet that can be turned off.
  (doorbells)