Magnetism

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Magnetism

• 1. History of Magnetism
• 2. Properties of Magnetism
• 3. Earth and Magnetism
• 4. Electricity and Magnetism

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1. History of Magnetism

• Naturally magnetized rock.
• According to myth a boy named Magnus discovered
  magnetite and named it after himself.
• Magnetite was actually named after Magnesia,
  Greece where it was first discovered.
• It was used in the first compasses.
• People thought it had healing powers.

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2. Properties of Magnets

• Have 2 poles- north and south
• Opposite poles attract (northsouth)
• Similar poles repel (N/N and S/S)
• When a magnet breaks in half each piece creates 2
  new poles.

South
North
N
S
N
N
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Properties of Magnets

• Making a magnet
• Magnetic Induction
• Ways to destroy a magnet
• Drop it
• Heat it
• Hit it

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Magnetic Fields

• Magnetic Fields are the invisible forces around
  magnets.

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Quick Quiz

• What rock is naturally magnetized?
• Where was magnetite first discovered?
• What poles attract?
• What is the myth about magnetite?
• What does a magnetic field look like??
• What mysterious power does magnetite supposedly
  have?

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Inside a Magnet

• is anything that takes up space.
• Matter
• Matter is made up of
• elements.
• The smallest part of an element is called an
• atom.
• An atom has a center called a
• nucleus.
• Inside the nucleus are
• protons
• which are positively charged particles.
• Outside of the nucleus are
• electrons which are
• negatively charged particles.

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Atom

• Center of the atom
• Nucleus
• Positively charged particles
• Protons
• Negatively charged particles
• electrons

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Inside a Magnet

• A magnet is created when the domains are aligned.
• When the domains are not in line then the object
  does not have a magnetic field.

Not a Magnet- domains not aligned
Magnet- domains aligned
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Quick Quiz II

• What does the domain look like inside a magnet?
• What is the smallest part of an element?
• What is matter?
• What is the center of an atom called?
• What is a proton?
• What is an electron?

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3. Earth as a Magnet

• Compass
• Magnetic N S pole
• Magnetosphere
• Aurora
• Mid-Ocean Ridge
• Magnetic Declination

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William Gilbert

• In the 1500s Sir William Gilbert suggested that
  the Earth acts like a giant magnet.

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Compasses

• Red needle in compass always points to magnetic
  north.
• Magnetic declination is the difference between
  magnetic north and true north.
• In Westerly, RI the magnetic declination is about
  12 degrees.
• Red Fred is in the shed.
• The Earth has two magnetic poles.

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Magnetosphere

• Solar Winds- flow of charged particles coming
  from the sun. These change the shape of the
  magnetosphere.

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Auroras

• Auroras are brightly colored lights in the sky
  caused by charged particles from solar winds
  getting into the atmosphere.

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Auroras are sometimes called the northern and
southern lights
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The aurora borealis is seen in the north while
the aurora australis is seen in the south.
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Mid-Ocean Ridge

• Place in the Atlantic ocean floor where lava from
  the core of the Earth comes to the surface and
  hardens to rock.
• There is proof here that the Earths magnetic
  poles have flipped every million years.

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Magnetic Declination- angle between true north
and where a compass points
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Magnetosphere

• The magnetosphere
• is the magnetic field surrounding the Earth.
• The magnetosphere protects us from
• solar winds.
• The magnetic north and south is where the solar
  winds break through and cause the
• auroras.
• The half of the magnetosphere facing the sun is
  squished. The other half is expanded and spread
  apart.

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Quick Quiz III

• How is an aurora formed?
• What does the magnetosphere do?
• How long do the magnetic poles take to switch
  usually?
• How many magnetic poles does the Earth have?
• What is magnetic declination?
• What does red Fred in the shed mean?

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Electricity and Magnetism

• Circuits
• Electric current
• Electromagnetism
• Motors

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Circuits

• Parts of a circuit
• Wires and Switch
• Resistor- device that uses electric energy
• Power source

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Material Types

• Conductor-
• material that allows electric current through
  easily.
• Insulators-
• materials that DONT allow electric currents
  through easily.

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Electromagetism

• Hans Christian Oersted discovered that a wire
  with a current running through it created a
  magnetic field. The wire made the compass needle
  move.

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Electromagnetism

• Add picture

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Electromagnets

• Solenoid
• current carrying coil of wire
• Core
• magnetic center
• SoleniodCore
• Electromagnet

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Electric Motors
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Parts of a Motor

• Three main parts
• Cap
• Casing
• Armature

• Permanent magnets
• Brushes
• Electromagnets
• Commutator
• Shaft

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How does an electric motor work?

• 1. Electric current goes from the battery to the
  brushes in the cap.
• 2. The brushes touch the commutator and the
  current goes into the solenoid.
• 3. The solenoid and core creates an electromagnet
  with the same pole as the permanent magnet it is
  next to.
• 4. The electromagnet repels from the permanent
  magnet it is next to causing the whole armature
  to turn.
• 5. The other brush touches the armature causing
  the opposite pole to be created.
• 6. This pole is the same as the permanent magnet
  it is next to causing the armature to continue
  spinning.