PHYSICS%20212%20Electricity%20and%20Magnetism

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PHYSICS 212 Electricity and Magnetism
1. Electric Fields

• Fundamental properties of electric charge
• Charging by induction and conduction
• Coulombs law and the electric force
• Electric fields
• Electric field lines
• Problems / Vectors

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Charge Conservation
Experiments show that

• Electric charge cannot be created nor destroyed
  
• CONSERVATION OF CHARGE
• Total charge of an object is always an integer
  multiple of a basic charge e
• CHARGE QUANTIZATION

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Types of Charge

• Two types of charge
• Named and -
• Like charges repel
• Unlike charges attract
• Repulsion and attraction are
  FORCES

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Forces on Charges
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Coulombs Law

• The force between charges is given byCOULOMBS
  LAW

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Meaning of Symbols

• Coulombs constant
• Unit vector pointing from charge 1 to charge 2
  
• The distance between the charges
• The force exerted on charge 2 by charge 1

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Atomic Structure

• Atoms
• Nucleus
• is very small less than 10-15 m in diameter,
  but heavy
• Contains protons and neutrons
• plus
• Electrons
• Diameter approx. 10-10 m
• are very light but make up the volume of the
  atom

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Materials

• Materials are atoms bound together by
  electrons
• Electrons are on the outside
• Produce the quality of Solidness
• Different materials hold their electrons with
  different forces
• Rubbing one material on the other displaces
  electrons
• one material becomes positive the other
  negative

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Charging by Induction
Charging by induction
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Charging by Conduction
Charging by conduction
- - - - - -


- - -
- - -

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Coulombs Law
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Force due to Many Sources

• at a point r
• The electric Force due to many point charge
  sources on a charge q
• is the vector sum of all forces due to source
  charges

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Diagram of Many Sources
F
F1
Q1
q
Q2
F2
r
F3
Q3
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Vector Sum
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Force Due to Continuous Source

• The Electric Force due to a continuous
  distribution of point charge
  sources
• A charged solid
• at a point r on a charge q
• is the vector integral of all forces due to
  the source charges

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Diagram of Continuous Source
F
q
Q
r
dF
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Vector Integral
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Electric Field
The Electric Field is the Force per unit charge
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Mathematical Expression
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Meaning of Symbols

• at a point r
• The Electric Field due to many point charge
  sources
• is the vector sum of all fields due to source
  charges

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Diagram of Field due to Point Sources
E1
Q1
E
E2
Q2
r
E3
Q3
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Vector Sum of Fields
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Diagram of Field Due to Continuous Source
E
Q
r
dE
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Vector Integral
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Electric Field Lines

• Electric Field lines are lines that have Electric
  Field vectors as tangent lines at each point.

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Picture of Field Lines
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Picture of Field Lines
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Picture of Field Lines
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Picture of Field Lines