Magnetic Fields

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Magnetic Fields
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• The forces between magnets, electrical charges,
  and masses act at a distance and are explained by
  magnetic fields, electrical fields, and
  gravitational fields.
• magnetic fields can be visualized by iron filings
  which become small magnets by induction and act
  like the needle of a compass.
• magnetic flux - the number of magnetic field
  lines passing through a surface. The flux per
  unit area is proportional to the strength of the
  magnetic field.

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Magnetic Field! (Shown by FLUX)
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The Earths Magnetic Field
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• The direction of the magnetic field lines is
  defined as the direction to which the N-pole of a
  compass points when it is placed in the magnetic
  field.

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More FLUX
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Right Hand Rule

• In 1820, the Danish physicist Hans Christian
  Oersted (1777-1851) discovered that electric
  currents in wires produced magnetic fields. The
  circular lines indicate that magnetic field lines
  form closed loops.
• You can find the direction of the field using the
  first right-hand rule.

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• The strength of the magnetic field around a long,
  straight wire is varies directly to the current
  flowing in the wire and inversely with the
  distance from the wire.
• electromagnet - consists of a coil of wire
  carrying a current usually wrapped around a bar
  or tube of iron.
• The right-hand rule indicates the N-pole of the
  magnet by the direction of the thumb.
• Increasing the number of loops in an
  electromagnet increases the strength of the
  magnetic field. The strength of the field of an
  electromagnet is proportional to the current and
  to the number of loops, and depends on the nature
  of the core.

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Application of the RHR
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Field Vectors, and the RHR
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FORCES CAUSED BY MAGNETIC FIELDS

• Michael Faraday (1791-1867), discovered that a
  wire with an electrical current flowing through
  it would experience a force at right angles to
  the direction of the magnetic field and the
  current. The direction of the force on a
  current-carrying wire in a magnetic field can be
  found by expanding the right-hand rule. The
  direction of Force is perpendicular and away from
  the palm.

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Field Vectors, the RHR and Magnetic Forces
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Finding the Strength of the Field

• The magnitude of the force is given by the
  formula F B I L
• Where F is Force B is magnetic Field Strength I
  is current
• L is the length of the wire that is in the
  magnetic field

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