Transcript Review 21-22

Quiz Thursday
• Ch.21-22
• one 3x5 inch card notes f/b (do not bring
larger)
• constants provided – units are not
provided
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Paul A. Tipler • Gene Mosca
Physics for Scientists
and Engineers
Fifth Edition
Chapter 21:
The Electric Field I:
Discrete Charge Distributions
Copyright © 2004 by W. H. Freeman & Company
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Electric Charge
qproton = +e
qneutron = 0
qelectron = -e
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Types of Materials
Materials covered
• Conductors
• Insulators
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Charging by Induction
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Electric Field
•
•
•
•
E = F/qo. (N/C = V/m)
lines leave (+) and enter (-)
F = qE.
E = E1 + E2 + … (sum of all E fields)
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Unit Vectors and E
Ex. Calculate unit vector
pointing from (1, 0) to (6, 2):
r1/r1 = {(6, 2) – (1, 0)}/(29). = (5,2)/ (29)
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Paul A. Tipler • Gene Mosca
Physics for Scientists
and Engineers
Fifth Edition
Chapter 22:
The Electric Field II: Continuous
Charge Distributions
Copyright © 2004 by W. H. Freeman & Company
9
E due to Charge Distributions
• E = integral of all charge-contributions
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Uniformly Charged Line of Charge:
Eqn. 22-8
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Uniformly Charged Disk
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Electric Flux
• Flux = integral E “dot” A
• Related to charge distribution
Case where E is spatially uniform:
• f = E·A = EAcosq.
• f = +EA (E,A in same direction)
• f = -EA (E, A in opposite direction)
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Flux & Lines of E
• equal lines  equal flux
• Ex. 4 lines  EA1cos0° = EA2cosq.
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Permittivity
 o  8.85 10 C / Nm
12
k
2
2
1
4o
fnet  4kQinside 
Qinside
o
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Ex. Gauss’s Law
E
1

2o R
fnet  fleft  fcyl  fright
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Uniformly Charged Sphere
Uniformly Charged Shell
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Discontinuity of E
En 
1
o
   4k
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E near conductor
• E = /o.
• perpendicular to surface
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