Electromagnetism

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Electromagnetism

• University of British Columbia
• Physics 420
• By Jason Cheung

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What is a Field?

• A region of space characterized by a physical
  property having a determinable value at every
  point in the region
• Examples gravitational field, Electric field
  ,and magnetic field

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Gravitational Field

• Defined as

A acceleration
G gravitational constant
r distance to the center of the big
object
m mass of big object
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Electric Field

• Electric field is defined as the electric force
  per unit Charge
• It is the surrounding charges that create an
  electric field

E Electric Field F Electric Force q Charge
E is measure in Force/Coulomb
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Cathode Ray Tube Demo (CRT)
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Magnetic Field

• Magnetic field is a field that exerts a force on
  a moving charge
• A magnetic field can be caused either by another
  moving charge or by a changing of electric field
  or magnetic dipoles of materials

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• Magnetic Field is measure in Tesla

A simple formula to calculate Magnetic Field
B magnetic field F Magnetic Force Q
charge V velocity of the moving charge
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Battery Demo
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• Charge moving in a magnetic field obeys the Right
  Hand Rule
• There are two types of RHR
• Right Hand Rule 1
• Right Hand Rule 2

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Right Hand Rule 1

• The thumb represents the velocity of which the
  charge is going
• The remaining fingers tell you the direction of
  the magnetic field
• example

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Right Hand Rule 2

• I direction of the charge
• B direction of the Magnetic Field
• F Force act on the charge
• Palm Push Positive (Remember!!)

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Right Hand Rule Question
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Magnetism

• What is magnetism?
• Magnetism is one of the phenomena by which
  materials exert an attractive or repulsive force
  on other materials.
• What causes magnetism in material?
• It is the unpaired electrons in the electron
  orbit cause magnetism

• example of pair and unpaired
• N is unpaired,
• O is paired (one of them)

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Remember SPDF?? (Chem 11)

• Electrons fall into electron shell according to
  Hunds rule.
• Examples

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Nitrogen
-Electrons
-Protons and Neutrons
1s2
2p3
2s2
Right
Electron Configuration of Nitrogen
Wrong
Wrong
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There are four types of magnetism

• 1.Ferromagnetic
• 2.Paramagnetic
• 3.Diamagnetic
• 4.Ferrimagnetic (Not going to cover)

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Magnetism is Measure in Magnetic Susceptibility
(?m)
The more susceptibility of a material has, the
more magnetic property it processes
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Ferromagnetic

• Any material that possess magnetization WITHOUT
  an external magnetic field is ferromagnetic
• large and positive susceptibility
• Examples of ferromagnetic materials

Cobalt (Co) Susceptibility 70
Iron (Fe) Susceptibility 200
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Iron electron configuration
Fe 1s2,2s2,2p6,3s2,3p6,4s2,3d6
Ar 1s2,2s2,2p6,3s2,3p6 Ar Core
Fe Ar,4s2,3d6
Ar
-The electrons seems to align spontaneously -Pure
quantum mechanics effect
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Why are some Ferromagnetic doesnt attract one
another?

• Has to do with the magnetic domain of the material

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Ferromagnetic material demo
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Paramagnetic

• Any material that possess magnetization (i.e.
  attraction with other magnetized material) WITH
  an external magnetic field is paramagnetic
• small and positive susceptibility
• Examples of paramagnetic materials

Aluminum Al Susceptibility 2.210-5
Platinum Pt
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Aluminum electron configuration
Ne.3s2.3p1
What is the differences between the two?!
Compare to Iron (Fe)
Ar
Fe Ar,4s2,3d6
the dipoles do not interact with one another and
are randomly oriented in the absence of an
external field due to thermal agitation,
resulting in zero net magnetic moment
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Paramagnetic and Ferromagnetic Demo (magnets and
levitation)
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Diamagnetic

• very weak and negative susceptibility to magnetic
  fields.
• Negative susceptibility repel against magnetic
  fields (diamagnetism)
• Positive susceptibility attract to magnetic
  fields (para ferromagnetism)

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Diamagnetism

• Examples of diamagnetic materials

Gold
Human (mostly)
Copper
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Diamagnetic Levitation Demo
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Applications of Magnetism
MRI (magnetic resonance images)
Superconductors
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Applications of Magnetism

• Maglev Trains