Potential difference in capacitor help

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Homework Help Overview

The problem involves a circuit with capacitors C_1, C_2, and C_3, where the switch transitions from position A to position B, affecting the charge and potential differences across the capacitors. Participants are exploring the implications of this switch on the charge distribution and potential differences after the transition.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the initial conditions of the capacitors and the effects of switching the circuit configuration. Questions arise about how to calculate the charge and potential differences after the switch is flipped, as well as the equivalent capacitance of the capacitors involved.

Discussion Status

Some participants have begun calculations based on the initial voltage and capacitance values, while others are questioning the assumptions regarding charge distribution after the switch is flipped. There is an ongoing exploration of the relationships between charge, capacitance, and potential difference.

Contextual Notes

Participants note that C_2 and C_3 are initially uncharged and that the problem consists of multiple parts, each requiring careful consideration of the circuit's behavior after the switch is flipped. There is a focus on the implications of connecting uncharged capacitors to a charged capacitor.

rayhan619
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Homework Statement



Initially, the switch in the figure is in position A and capacitors C_2 and C_3 are uncharged. Then the switch is flipped to position B. (Figure attached)
a) Afterward, what is the charge on C_1 capacitor?
b) Afterward, what is the potential difference across C_1 capacitor?
c) Afterward, what is the charge on C_2 capacitor?
d) Afterward, what is the potential difference across C_2 capacitor?
e) Afterward, what is the charge on C_3 capacitor?
f) Afterward, what is the potential difference across C_3 capacitor?

Homework Equations



V= IR

The Attempt at a Solution



How do I start this problem?
 
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rayhan619 said:
... (Figure attached)
... How do I start this problem?

This would be a start.
 


and here is the figure...
 

Attachments

  • 1.jpg
    1.jpg
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So what do you think is going to happen?

What is the equivalent capacitance of the additional capacitors that are not initially connected?
 


we know C = Q/V
V = 100 V
C1 = 15*10^-6 F
so Q = C1V = 100 V(15*10^-6 F) = 1.5*10^-3 C

C2 and C3 is in series. so 1/C = (1/C2 + 1/C3) = (1/30*10^-6)+(1/30*10^-6) = 66666.67
so C = 1.5*10^-5

would the Q be same after switching to point b? If yes, then we can figure out V using above equation.
 


rayhan619 said:
we know C = Q/V
V = 100 V
C1 = 15*10^-6 F
so Q = C1V = 100 V(15*10^-6 F) = 1.5*10^-3 C

C2 and C3 is in series. so 1/C = (1/C2 + 1/C3) = (1/30*10^-6)+(1/30*10^-6) = 66666.67
so C = 1.5*10^-5

would the Q be same after switching to point b? If yes, then we can figure out V using above equation.

When the connection is broken then there is a fixed charge on the C1. When the switch connects to C2 and C3 then the charge will be shared according to what the equivalent capacitance for all 3 of them.

C2 and C3 = 2*C1

C2 and C3 equivalent C = C1

When you put them in || you have then C1 + C1 = 2 C1

Q = V*C

So with the new C = 2*old C and charge the same, then Vnew = 1/2*Vold
 


there are like 6 parts of this problem.
so for part a)
C = Q/V
V = 100 V
C1 = 15*10^-6 F
so Q = C1V = 100 V(15*10^-6 F) = 1.5*10^-3 C
and how do I get the potential difference?
 


When uncharged capacitors are connected to the charged capacitors the common potential difference is given by V = (C1V1 + o)/(C1 + C2)
 

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