Unit_01_3_Web_Lecture_Notes

# Unit_01_3_Web_Lecture_Notes - line representation of the...

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Notes from lecture: 25 Jan 2008. The electric force on a point particle with charge q in an external electric field ext E r (by external, we mean that the field ext E r is not due to the particle itself) is given by ext E q F r r = . So if 0 > q , then ext E r and F r point in the same direction, while 0 < q would mean that ext E r and F r point in opposite directions. Since the electric field is a vector field, we sometimes draw it as a collection of arrows. In such a representation, the relative length of the arrows at different locations is proportional to the relative magnitude of the field at those locations. For example, the vector field representation for the electric field due to a stationary point particle with charge 0 > q looks like: An equivalent way to represent electric fields is to use lines rather than arrows. See the handout Electric Field Line Model for a discussion of the rules for this representation. The electric field

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Unformatted text preview: line representation of the electric field above is ext E r ext E r F r F r q > 0 q < 0 Imagine that, instead of a point particle, the charge > q were to be distributed uniformly on the surface of a spherical shell. By symmetry, the field outside the shell must be the same as that of a point charge, as shown below. The field is zero everywhere inside the shell. Therefore, the magnitude of the field due the charged spherical shell has a discrete jump at the surface of the shell (see below) Since the electric field obeys the superposition principle, you can use the above discussion about field due to a charged spherical shell to describe a charged solid sphere. To do so, represent the solid sphere as a sequence of concentric spherical shells. To find the total field at any one point, simply add the values of the field due to each of the concentric shells....
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## This note was uploaded on 05/15/2008 for the course PHYS 2208 taught by Professor Fulbright, r during the Spring '07 term at Cornell.

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Unit_01_3_Web_Lecture_Notes - line representation of the...

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