+ PROBLEM: How to find for CONTINUOUS source(s) (Sect. 3.3.2)?

+ Continuous charge distribution
line charge density , (C/m); charge
surface charge density , ; charge
volume charge density , ; charge

+ line charge:
surface charge:
volume charge:
Keys: Pick a convenient coordinates; determine dl, dS or dv (note: these are scalars).
Write position vector of the observation point (fixed), i.e. a fixed vector from the origin to the point of interest.
Write position vector of the source point (varying along the source), i.e. the vector that starts from the origin and scans over the charged object.
Exploit symmetry of charge distribution and expand unit vectors into rectangular ones if necessary.
Example 3.2: Coulomb's law for a continuous line charge
Example 3.4: Coulomb's law for a continuous ring of charges

+ Steps (Sect 3.3): Pick a convenient coordinates,
Use dl, ds or dv depending on the type of sources,
Identify the position vector of the observation point (a variable), the position vector of the source point (the integration variable disappearing after integration) and compute the distance between observation point and each source point .

+ to V (Sect 3.5): work or energy with
relative ; absolute
Example 3.5: Absolute potential for a point

+ V to : Maxwell's equation,
So is irrotational or conservative
Stroke's theorem implies
Path independent --

+ system of point charges:
Example 3.6: Potential of a system of point charges
line charge:
surface charge:
volume charge:
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HW #14	Due 3/29/07