Engineering Electromagnetics 1 0909'301'0102 Autumn 2001

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Engineering Electromagnetics 10909.301.01/02
Autumn 2001
Lecture 4aSeptember 25, 2001

• Prof. Peter Mark Jansson MScEng PP PE
• ECE Department
• Rowan University
• http//engineering.rowan.edu/jansson/autumn01/eem
  ag1/

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Plan
9/25/00

• Quiz 1 Grade Distribution
• Electrostatics
• Review Key Concepts
• Recall Battle Plan
• Discrete (Point) Charges
• Electric Field and Potential
• Spherical Coordinate System
• Line Charge
• Plane Charge

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Distribution
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EEMAG-1 Topics Today
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Recall Battle Plan
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Recall Coulombs Law

• Electric Force between 2 charges
• Where r is distance between the two charges
• And the unit vector is in the direction pointing
  from charge 1 toward the charge 2

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Spherical Coordinate System
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Example 1

• Two charges
• 0.7 mC at (2,3,6)
• 4.9 ?C at (0,0,0)
• What is force acting on the 0.7 mC charge?

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N Point Charges

• Electric Field due to N point charges
• Where rn is distance between observation point
  and nth charge
• And the unit vector is in the direction pointing
  from the nth charge toward the observation point

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Example 2

• Three charges
• 200 nC at (0,0,0)
• 200 nC at (2,0,0)
• 200 nC at (0,2,0)
• What is total force acting on a 500 nC charge
  located at (2,2,0)?

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Example 3

• Two charges
• 20 nC at (1,0,0)
• -20 nC at (0,1,0)
• What is E-field intensity in free space at (0,0,1)

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Recall Spherical Coordinate System
DEMOchargedist
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Point Charges

• Superposition principle
• Equipotential spherical surfaces surround each
  point charge
• E-field proportional to

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Recall Cylindrical Coordinate System
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Line Charge

• Electric Field due to Line Charge
• Where ?l is the electric charge in coulombs per
  meter
• And the unit vector ? is in the direction
  pointing from the line charge toward the
  observation point

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Example 4

• Line charge from z 0 to ?
• Uniform 100 nC/m
• What is E-field intensity in free space at
  (0,0,2)? What is force on a charge of 1 ?C
  placed there?

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Line Charge

• Equipotential cylindrical surfaces surround a
  uniformly charged line
• E-field proportional to

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Recall Cylindrical Coordinate System
DEMOchargedist
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Plane Charge

• Electric Field due to Plane Charge
• Where ?s is a uniform electric charge density in
  coulombs per square meter
• And the unit vector x is in the direction
  pointing from the plane charge toward the
  observation point

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Plane Charge

• Constant Vector independent of coordinates
  pointing away from the plane
• E-field proportional to

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Summary