Introduction to Physical Systems Dr. E.J. Zita, The Evergreen State College, 30.Sept.02 Lab II Rm 2272, [e-mail], 360-867-6853

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Introduction to Physical SystemsDr. E.J. Zita,
The Evergreen State College, 30.Sept.02Lab II Rm
2272, zita_at_evergreen.edu, 360-867-6853
Program syllabus, schedule, and details online at
http//academic.evergreen.edu/curricular/physys/06
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Zita_at_evergreen.edu, 2272 Lab II TA Jada Maxwell
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Introduction to ElectromagnetismDr. E.J. Zita,
The Evergreen State College, 16.Jan.2007

• 4 realms of physics
• 4 fundamental forces
• 4 laws of EM
• statics and dynamics
• conservation laws
• EM waves
• potentials
• Ch.1 Vector analysis
• Ch.2 Electrostatics

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4 realms of physics, 4 fundamental forces
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Four laws of electromagnetism
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Electrostatics

• Charges make E fields and forces
• charges make scalar potential differences dV
• E can be found from V
• Electric forces move charges
• Electric fields store energy (capacitance)

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Magnetostatics

• Currents make B fields
• currents make magnetic vector potential A
• B can be found from A
• Magnetic forces move charges and currents
• Magnetic fields store energy (inductance)

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Electrodynamics

• Changing E(t) make B(x)
• Changing B(t) make E(x)
• Wave equations for E and B
• Electromagnetic waves
• Motors and generators
• Dynamic Sun

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Some advanced topics

• Conservation laws
• Radiation
• waves in plasmas, magnetohydrodynamics
• Potentials and Fields
• Special relativity

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Ch.1 Vector Analysis
Dot product A.B Ax Bx Ay By Az Bz A B
cos q Cross product AxB A B sin q
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Examples of vector products

• Dot product work done by variable force

• Cross product
• angular momentum
• L r x mv

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Differential operator del

• Del differentiates each component of a vector.
• Gradient of a scalar function slope in each
  direction
• Divergence of vector dot product what flows
  out
• Curl of vector cross product circulation

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Practice 1.15 Calculate the divergence and
curl of v x2 x 3xz2 y - 2xz z
Ex If v E, then div E charge if v B,
then curl B current.
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Separation vector differs from position vector
Position vector location of a point with
respect to the origin.
Separation vector from SOURCE (e.g. a charge at
position r) TO POINT of interest (e.g. the place
where you want to find the field, at r).
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Ch.2 Electrostatics charges make electric
fields

• Charges make E fields and forces
• charges make scalar potential differences dV
• E can be found from V
• Electric forces move charges
• Electric fields store energy (capacitance)

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Gauss Law practice
What surface charge density does it take to make
Earths field of 100V/m? (RE6.4 x 106 m) 2.12
(p.75) Find (and sketch) the electric field E(r)
inside a uniformly charged sphere of charge
density r.
2.21 (p.82) Find the potential V(r) inside and
outside this sphere with total radius R and total
charge q. Use infinity as your reference point.
Compute the gradient of V in each region, and
check that it yields the correct field. Sketch
V(r).