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Unformatted text preview: capacitor with the smaller C has the
larger V.
IDENTIFY:! The two capacitors are in parallel so the voltage is the same on each, and equal to the applied voltage Vab .
SET UP:! Do parts (a) and (b) together. The network is sketched in Figure 24.17.
EXECUTE:! V1 # V2 # V V1 # 52.0 V
V2 # 52.0 V
Figure 24.17 C # Q / V so Q # CV
Q1 # C1V1 # . 3.00 $ F /. 52.0 V / # 156 $ C. Q2 # C2V2 # . 5.00 $ F / . 52.0 V / # 260 $ C.
EVALUATE:! To produce the same potential difference, the capacitor with the larger C has the larger Q. 246 Chapter 24 24.18. IDENTIFY:! For capacitors in parallel the voltages are the same and the charges add. For capacitors in series, the
charges are the same and the voltages add. C # Q / V .
SET UP:! C1 and C2 are in parallel and C3 is in series with the parallel combination of C1 and C2 .
EXECUTE:! (a) C1 and C2 are in parallel and so have the same potential across them: Q2 40.0 " 10!6 C
#
# 13.33 V . Therefore, Q1 # V1C1 # (13.33 V)(3.00 " 10!6 F) # 80.0 " 10!6 C . Since C3 is
C2 3.00 " 10!6 F
in series with the parallel combination of C1 and C2 , its charge must be equal to their combined charge:
V1 # V2 # 24.19. 24.20. C3 # 40.0 " 10!6 C 0 80.0 " 10!6 C # 120.0 " 10!6 C .
1
1
1
1
1
(b) The total capacitance is found from
and Ctot # 3.21 $ F .
#
0
#
0
!6
Ctot C12 C3 9.00 " 10 F 5.00 " 10!6 F
Q
120.0 " 10!6 C
Vab # tot #
# 37.4 V .
Ctot
3.21 " 10!6 F
Q 120.0 " 10!6 C
EVALUATE:! V3 # 3 #
# 24.0 V . Vab # V1 0 V3 .
C3 5.00 " 10!6 F
IDENTIFY and SET UP:! Use the rules for V for capacitors in series and parallel: for capacitors in parallel the voltages
are the same and for capacitors in series the voltages add.
EXECUTE:! V1 # Q1 / C1 # .150 $ C / / . 3.00 $ F / # 50 V
C1 and C2 are in parallel, so V2 # 50 V
V3 # 120 V ! V1 # 70 V
EVALUATE:! Now that we know the voltages, we could also calculate Q for the other two capacitors.
1
1
1
!A
IDENTIFY and SET UP:! C # 0 . For two capacitors in series,
#0
.
Ceq C1 C2
d...
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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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