Magnetic Fields

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Magnetic Fields
By Engr. Hinesh Kumar Lecturer I.B.T, LUMHS
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Magnetism
Since ancient times, certain materials, called
magnets, have been known to have the property of
attracting tiny pieces of metal. This attractive
property is called magnetism.
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Magnetic Poles
The strength of a magnet is concentrated at the
ends, called north and south poles of the
magnet.
A suspended magnet N-seeking end and S-seeking
end are N and S poles.
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Magnetic Attraction-Repulsion
attraction
repulsion
Magnetism is the force of ___________ or
___________ of magnetic materials.
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Magnetic Attraction-Repulsion
Magnetic Forces Like Poles Repel
Unlike Poles Attract
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Magnetic Field

• A field of force surrounding a permanent magnet
  or a moving charged particle, in which another
  permanent magnet or moving charge experiences a
  force
• The lines of force surrounding a permanent magnet
  or a moving charged particle.
• Its a vector quantity. 
• Its units Tesla, Gauss

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Magnetic Field
magnetic field
A __________ ______ is an area around a magnet
that applies a force to magnetic materials
without touching them.
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The magnetic field actually keeps going out
forever, it just gets weaker the farther away
from the magnet it is.
It eventually gets too weak to move anything.
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Magnetic Field Lines
We can describe magnetic field lines by imagining
a tiny compass placed at nearby points.
The direction of the magnetic field B at any
point is the same as the direction indicated by
this compass.
Field B is strong where lines are dense and weak
where lines are sparse.
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Properties

• Magnetic field lines are continuous and unbroken,
  forming closed loops. 
• A magnetic field line can never cross another
  field line
• Magnetic field lines are defined to begin on the
  north pole of a magnet and terminate on the south
  pole.
• If magnetic monopoles existed, then magnetic
  field lines would begin and end on them.

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Field Lines Between Magnets
Unlike poles
Attraction
Leave N and enter S
Repulsion
Like poles
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Electromagnets

• Electromagnets
• An electromagnet is formed when a ________ in an
  electric circuit is wrapped around an _____ _____
  producing a magnetic field.
• The magnet that results loses its magnetism if
  the electric current ______ ________.
• Electric current is simply the flow of
  ______________.
• (or the flow of charged particles, like
  electrons)

wire
iron core
stops flowing
electricity
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• Generators
• A generator changes ____________ energy into
  ___________ energy when a coil of wire is rotated
  near a magnet.

mechanical
electrical
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• Simple Electric Motors
• A motor changes ___________ energy into
  ____________ energy by rotating
• an electromagnet between _______ of a magnet.

mechanical
electrical
poles
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• How it works
• The coil of the electromagnet is connected to a
  source of ___________.
• When electricity flows through the electromagnet,
  a ___________ field is produced.

electricity
magnetic
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attached
spin

• The rotating coil of wire can be _________ to an
  object to make it _____.
• Examples ________ on an electric car, ___
  blades, a ______ ____.

wheels
fan
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attached
spin

• The rotating coil of wire can be _________ to an
  object to make it _____.
• Examples ________ on an electric car, ___
  blades, a ______ ____.

disco ball
wheels
fan
But, what good is a disco ball without lights or
music?