Voltage of a Capacitor using Kirchhoff's Loop Rule

In summary, the conversation discusses using Kirchhoff's Loop Rule to solve for the voltages of five capacitors in a network. The solution requires a system of equations, but it is important to ensure the number of equations matches the number of unknowns. It is also important to consider all possible loops in the network.
  • #1
unknownv2
1
0
(Sorry, meant to post this in Introductory Physics Homework, if someone could please move it.)


1. Homework Statement


Use Kirchhoff's Loop Rule to solve for the voltages of the five capacitors in the network shown below.

Z36ydF0.jpg

Homework Equations



For Capacitance, C = q/v
Kirchoff's juction law states that the total current into a junction must equal the total current leaving the function and that the sum of the potential differences around any loop or closed path is zero.

08d7bd7060be987d4da37b7fc263a740.png


The Attempt at a Solution


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My work can be found here: (Warning large image)

https://i.imgur.com/RMDZrAP.jpg

The solution requires a system of equations to solve and I have:

1) ## -V_1 - V_5 - V_2 + V_A = 0##
2) ## -V_3 - V_5 - V_4 + V_A = 0##
3) ## -Q_5 + Q_4 + Q_2= 0##
4) ## -Q_1 - Q_3 + Q_5= 0##1 and 2 translate to:
1) ##\frac{-Q_1}{C_1} + \frac{-Q_5}{C_5} + \frac{-Q_2}{C_2} + 24 = 0##
2) ##\frac{-Q_3}{C_3} + \frac{-Q_5}{C_5} + \frac{-Q_4}{C_4} + 24 = 0##

It doesn't seem possible to solve those system of equations so I assume I messed up somewhere on creating the equations.Questions:

1) Can an open/close loop be created by the voltage connections on both sides of the capacitor, without necessarily returning to the original entrance of the voltage? Such as, if the voltage enters on the left side, can it leave through the right? I'm thinking enters from left (##V_L##) to ##C_1## through ##C_5## then ##C_4## then out the right (##V_R##) side, as an example?

2) How many equations would be needed for the system of equations? Does that depend on the number of junctions or the number of capacitors? So would I need 5 equations total before I can solve this?
 

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  • #2
Hello V, welcome to PF :smile: !

You either want to reduce the number of unknowns or increase the number of equations.

As to the first: if you pick the voltage at two smart points you can described all the voltage differences
As to the second: there's more loops to be found than you now mention -- that should also answer your first question: think loops, not paths
 
  • #3

1. What is Kirchhoff's Loop Rule and how does it apply to capacitors?

Kirchhoff's Loop Rule, also known as Kirchhoff's Voltage Law, states that the sum of the voltage drops around a closed loop in a circuit must equal the sum of the voltage sources in that loop. This rule applies to capacitors because they store and release electrical energy, resulting in changes in voltage within the circuit.

2. How do you calculate the voltage of a capacitor using Kirchhoff's Loop Rule?

To calculate the voltage of a capacitor using Kirchhoff's Loop Rule, you need to first draw a circuit diagram and identify all the voltage sources and their directions. Then, use the equation V = Q/C, where V is the voltage, Q is the charge on the capacitor, and C is the capacitance. Finally, use Kirchhoff's Loop Rule to set up an equation with all the voltage drops and sources, and solve for the voltage of the capacitor.

3. Can Kirchhoff's Loop Rule be applied to circuits with multiple capacitors?

Yes, Kirchhoff's Loop Rule can be applied to circuits with multiple capacitors. Each capacitor will have its own voltage drop, which can be calculated using the equation V = Q/C. The total voltage of the circuit can be found by adding up all the voltage drops and sources using Kirchhoff's Loop Rule.

4. How does the voltage of a capacitor change over time?

The voltage of a capacitor changes over time as it charges or discharges. When a capacitor is connected to a voltage source, it begins to charge and its voltage increases. As it reaches its maximum voltage, it stops charging and remains at that voltage until it is disconnected from the source. When a capacitor is disconnected, it begins to discharge and its voltage decreases over time.

5. What factors affect the voltage of a capacitor in a circuit?

The voltage of a capacitor in a circuit is affected by the capacitance of the capacitor, the charge on the capacitor, and the voltage sources in the circuit. The capacitance determines how much charge a capacitor can store, while the charge on the capacitor determines its current voltage. The voltage sources in the circuit can either increase or decrease the overall voltage of the capacitor depending on their directions and magnitudes.

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