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Unformatted text preview: apacitors in Parallel
V1 = V2 = V3 (same potential top and bottom)
Total charge: Qtot = Q1 + Q2 + Q3
CeqV = C1V + C2V + C3V Ceq = C1 + C2 + C3
Basic law for combining
capacitors in parallel
Works for N capacitors
PHY2049: Chapter 25 12 Capacitors in Series
q1 = q2 = q3 (same current charges all capacitors)
Total potential: V = V1 + V2 + V3
q/Ceq = q/C1 + q/C2 + q/C3 1
1
1
1
=
+
+
Ceq C1 C2 C3
Basic law for combining
capacitors in series
Works for N capacitors PHY2049: Chapter 25 13 ConcepTest
Two identical parallel plate capacitors are shown in an
endview in Figure A. Each has a capacitance of C.
If the two are joined together at the edges as in Figure B,
forming a single capacitor, what is the final capacitance?
(a) C/2
(b) C
(c) 2C
Area is doubled
(d) 0
(e) Need more information A
PHY2049: Chapter 25 B
14 ConcepTest
Each capacitor is the same in the three configurations.
Which configuration has the lowest equivalent capacitance?
(1)
(2)
(3)
(4) A
C/2 (series)
B
C
They all have identical capacitance C C C C C
A B
PHY2049: Chapter 25 C
15 Energy in a Capacitor
Capacitors have energy associated with them
Grab a charged capacitor with two hands and find out! Calculate energy
Continually move charge from – to + surface
dU = V dQ
Q
Q2 1
2
V=Q/C U =
Q / C dQ =
= CV ∫0 ( ) 2C 2 Q2 1
U=
= 2...
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This note was uploaded on 07/31/2011 for the course PHY 2049 taught by Professor Any during the Summer '08 term at University of Florida.
 Summer '08
 Any
 Physics, Capacitance, Charge, Electric Fields

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