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Unformatted text preview: es add; Ceq # C1 0 C2 0 % C # (b) From Figure 24.57c, Qtot # CeqV # (2.19 "10!6 F)(12.0 V) # 2.63"10!5 C. From Figure 24.57b, Qtot # 2.63 "10!5 C.
Q4.8 2.63 " 10!5 C
#
# 5.48 V . U 4.8 # 1 CV 2 # 1 (4.80 " 10!6 F)(5.48 V)2 # 7.21" 10!5 J # 72.1 $ J
2
2
C4.8 4.80 " 10!6 F
This one capacitor stores nearly half the total stored energy.
Q2
EVALUATE:! U #
. For capacitors in series the capacitor with the smallest C stores the greatest amount of
2C
energy.
V4.8 # Figure 24.57
24.58. IDENTIFY:! Apply the rules for combining capacitors in series and parallel. For capacitors in series the voltages add
and in parallel the voltages are the same.
SET UP:! When a capacitor is a moderately good conductor it can be replaced by a wire and the potential across it is zero.
EXECUTE:! (a) A network that has the desired properties is sketched in Figure 24.58a. Ceq # C 0 C # C . The total
22
capacitance is the same as each individual capacitor, and the voltage is spilt over each so that V # 480 V.
(b) If one capacitor is a moderately good conductor, then it can be treated as a “short” and thus removed from the
circuit, and one capacitor will have greater than 600 V across it.
EVALUATE:! An alternative solution is two in parallel in series with two in parallel, as sketched in Figure 24.58b. Figure 24.58 2416 Chapter 24 24.59. (a) IDENTIFY:! Replace series and parallel combinations of capacitors by their equivalents.
SET UP:! The network is sketched in Figure 24.59a. C1 # C5 # 8.4 $ F
C2 # C3 # C4 # 4.2 $ F
Figure 24.59a
EXECUTE:! Simplify the circuit by replacing the capacitor combinations by their equivalents: C3 and C4 are in series and can be replaced by C34 (Figure 24.59b):
1
1
1
#
0
C34 C3 C4
1
C 0 C4
#3
C34
C3C4
Figure 24.59b
C34 # C3C4
. 4.2 $ F /. 4.2 $ F / # 2.1 $ F
#
4.2 $ F 0 4.2 $ F
C3 0 C4 C2 and C34 are in parallel and can be replaced by their equivalent (Figure 24.59c):
C234 # C2 0 C34
C234 # 4.2 $ F 0 2.1 $ F
C234 # 6.3 $ F
Figure 24.5...
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This document was uploaded on 03/11/2014 for the course PHYSICS 240 at University of Michigan.
 Fall '08
 DaveWinn
 Physics

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