Hw: All Chapter 3 problems and exercises Reading: Chapter 3.
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Transcript of Hw: All Chapter 3 problems and exercises Reading: Chapter 3.
Chapter 2 hw quiz
What is the electric field at the center of a circle of radius R if the top half of the circle has a uniform charge +Q spread over the perimeter and the bottom half has a negative charge, -Q, uniformly spread over the perimeter?
+Q
-Q
One-dimensional problem:
dxxFWx
x
)(2
1
dx
dUxF )(
dxdx
dUx
x
2
1
)]()([ 12 xUxU
P218 Review: Conservative forces
Two-dimensional problem:
dyFdxFrdFWr
r
y
r
r
x
r
r 2
1
2
1
2
1
)]()([ 12 rUrU
y
UF
x
UF yx
;
veconservatiW does NOT depend on path!
veconservatiW around the closed path is zero!
Chapter 3. Electric Potential
• Constant electric field
• The Electric Potential: V
- Single Charge
- Dipole
EqF
- conservative? potential energy function?
)]()([)]()([1
lim 12120
00
2
1
rVrVrUrUq
rdEq
r
r
ExxVConstE )(
For a point charge at the origin:
r
qrV
04
1)(