Conductors

1
Conductors
2
Reminder
For sheets of charge
s Q/A
?0 8.8x10-12 C2/Nm2
For large plates (or close distances), the
strength of the field does NOT depend on distance
from the plate.
3
Field lines for a Plate
?()
4
Two Parallel Plates
5
Two Parallel Plates
?()
6
Two Parallel Plates
Enet
?()
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Two Parallel Plates
Enet
Enet
?()
8
Two Parallel Plates
Enet
Enet
?()
Enet 0
9
What do the field lines look like?
?()
10
How big is E?
Enet
?()
11
How big is E?
?()
12
0
Prob. 27 Points A and B are located as shown
between two large uniformly charged parallel
plates. Which of the following correctly
describes what happens to the electric fields at
A and B if the plate on the right (-Q) is removed?
a. The field at A drops more than the field at
B. b. The field at B drops more than the field at
A. c. Both fields remain the same. d. Both fields
drop by the same amount.
13
?()
0
Symmetry
2 infinite insulating sheets with fixed charge.
14
0
One day, Greg, Ill be sitting at that desk.
15
?()
0
B
2 infinite insulating sheets with fixed charge.
SUPERPOSITION
16
0
B
What direction is the electric field to the
bottom plate?
17
?()
0
B
What direction is the electric field to the side
plate? How long is is compared to the one from
the bottom plate?
18
?()
0
B
19
?0 Q/A
Charged conducting plate
0
Whats wrong with this picture?
20
Charged conducting plate
?0 Q/A
0
?L ?0/2
?R ?0/2
Free charge always goes to surface of conductor.
21
Charged conducting plate
?0 Q/A
0
?L ?0/2
?R ?0/2
EL ?L/2e0
EL ?0/4e0
What is the electric field inside the conductor?
22
Charged conducting plate
?0 Q/A
0
?L ?0/2
?R ?0/2
What is the electric field inside the conductor?
23
Charged conducting plate
?0 Q/A
0
?L ?0/2
?R ?0/2
The electric field is zero everywhere inside the
conductor.
What is the electric field inside the conductor?
24
0
The charge on a conductor will always
redistribute to keep the electric field zero
inside the conductor.
E-M Shielding
25
Electroscope
0
26
0
27
Faradays Bucket
0
28
0
29
0
Boston Museum of Science
30
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