# Solving Circuit: Find Total Capacitance & Understand Repercussions

• MathewsMD
In summary, the conversation was about trying to solve a circuit with four capacitors in which the total capacitance needed to be determined. The person seeking help was having trouble simplifying the circuit due to the multiple possible paths for current to flow. A suggestion was made to re-draw the circuit with the 4uF and 6uF capacitors horizontally and the two series capacitors in the middle. This would allow for easier identification of nodes and components. However, the person was still having trouble understanding this method and requested further clarification or a visual aid.
MathewsMD
I've been trying to solve this circuit but cannot come up with any proper circuit that depicts this is in a simplified form that would help me solve for the total capacitance of the system. I just find it odd since current can go both "up" and "down" through the two middle capacitors and it seems like there would be repercussions to the circuit (are there any?). I've been trying to deduce the capacitance by creating different arrangements but it just seems like there are too many possible paths for the current to flow. Any help would be greatly appreciated!

MathewsMD said:
I've been trying to solve this circuit but cannot come up with any proper circuit that depicts this is in a simplified form that would help me solve for the total capacitance of the system. I just find it odd since current can go both "up" and "down" through the two middle capacitors and it seems like there would be repercussions to the circuit (are there any?). I've been trying to deduce the capacitance by creating different arrangements but it just seems like there are too many possible paths for the current to flow. Any help would be greatly appreciated!

Was there supposed to be an attachment?

berkeman said:
Was there supposed to be an attachment?

Hi,

Oh wow, sorry, I just realized it didn't attach properly. Yes, here it is:

#### Attachments

• Screen Shot 2014-02-12 at 3.27.19 PM.png
2.2 KB · Views: 356
Ah, that helps. They are just trying to confuse you with the way they are drawing it.

Try this... Re-draw the circuit with the 4uF cap horizontally across the top, the 6uF cap horizontally across the bottom, and the two series caps horizontally across the middle. Be sure to keep the wires connected the same, so that the connections don't change. You end up with more of a horizontal rectangular circuit drawing.

Now, do you see some simplifications?

berkeman said:
Ah, that helps. They are just trying to confuse you with the way they are drawing it.

Try this... Re-draw the circuit with the 4uF cap horizontally across the top, the 6uF cap horizontally across the bottom, and the two series caps horizontally across the middle. Be sure to keep the wires connected the same, so that the connections don't change. You end up with more of a horizontal rectangular circuit drawing.

Now, do you see some simplifications?

I've tried to follow what you've said but doubt I fully understood what you meant...
Here's my following drawing but as you can already see, it is not the same circuit. I'm just not seeing how this can be easily decomposed yet.

Sorry for the hassle, but do you mind elaborating a little bit or showing a rough sketch please since I don't think I quite understood the transformation you wanted me to make?

#### Attachments

• Screen Shot 2014-02-12 at 8.14.37 PM.png
4 KB · Views: 391
Last edited:
Try this: Identify all the nodes and place a label on them (hint: Nodes a and b already have a label, and there's only one more. Remember that any contiguous wiring comprises the same node). Then make a list of all the components and the two nodes that they connect to. So for example the 4 μF capacitor connects to nodes a and b.

Now forget the original diagram and use the list to construct a new circuit diagram with the same node associations for each component. What do you come up with?

gneill said:
Try this: Identify all the nodes and place a label on them (hint: Nodes a and b already have a label, and there's only one more. Remember that any contiguous wiring comprises the same node). Then make a list of all the components and the two nodes that they connect to. So for example the 4 μF capacitor connects to nodes a and b.

Now forget the original diagram and use the list to construct a new circuit diagram with the same node associations for each component. What do you come up with?

Hmmm...

Let me see if I did this right.

Despite doing this, I just don't see how this helps with the simplification exactly...

#### Attachments

• Screen Shot 2014-02-12 at 8.52.23 PM.png
14.2 KB · Views: 399
• Screen Shot 2014-02-12 at 8.47.23 PM.png
4.9 KB · Views: 370
Can you share your list of components and node associations? (If you want you can combine the 7 and 5 μF capacitors into a single capacitor right away, since that combination is rather obvious from the original figure).

gneill said:
Can you share your list of components and node associations? (If you want you can combine the 7 and 5 μF capacitors into a single capacitor right away, since that combination is rather obvious from the original figure).

Okay. Yes, I understand those 2 are in series. In the first image posted in the 7th post in this thread, I made black dots to represent nodes on the original image.

MathewsMD said:
Okay. Yes, I understand those 2 are in series. In the first image posted in the 7th post in this thread, I made black dots to represent nodes on the original image.

Okay, well you've added dots to the top of the circuit, but they are still node b... remember, contiguous wire paths comprise a single node. You can trace a path from your dot to the terminal marked 'b' without passing through any components. So it's still node b.

So, how about writing out that list of components and which nodes they connect to?

gneill said:
Okay, well you've added dots to the top of the circuit, but they are still node b... remember, contiguous wire paths comprise a single node. You can trace a path from your dot to the terminal marked 'b' without passing through any components. So it's still node b.

So, how about writing out that list of components and which nodes they connect to?

There are two paths it can go from the top junction, though, right? Does not that mean it can be considered as a node? I'm sorry but do you mind providing some sort of visual aid on how you would go about solving this since I'm beginning to become a little confused with the wording.

MathewsMD said:
There are two paths it can go from the top junction, though, right? Does not that mean it can be considered as a node?
It's a node, but it's the same node as terminal b since there's a contiguous wire path from there to b.

I'm sorry but do you mind providing some sort of visual aid on how you would go about solving this since I'm beginning to become a little confused with the wording.

Identify the contiguous wire "islands" where components connect. They will be your nodes:

#### Attachments

• Fig1.gif
2.9 KB · Views: 519
gneill said:
It's a node, but it's the same node as terminal b since there's a contiguous wire path from there to b.

Identify the contiguous wire "islands" where components connect. They will be your nodes:

Thank you for the drawing! It definitely clarifies what you meant by the nodes. Now, despite that, I still seem to have some trouble actually drawing the circuit. I've come up with the follow circuit but it is still incorrect. Any further ideas?

#### Attachments

• Screen Shot 2014-02-12 at 10.10.08 PM.png
2.8 KB · Views: 354
List your components and node associations. The 6 μF capacitor connects to nodes...

Does someone please mind showing me the solution for this? I keep trying but can't seem to figure it out. I'd just like to learn the steps on how to simplify it. Any drawings would be extremely helpful! :)

MathewsMD said:
Does someone please mind showing me the solution for this? I keep trying but can't seem to figure it out. I'd just like to learn the steps on how to simplify it. Any drawings would be extremely helpful! :)

We can't do your homework for you here. Providing complete solutions is against the rules. We can only give hints, suggestions to follow, and point out errors or misconceptions.

Drawings have been provided! Suggestions have been provided! Try them!

gneill said:
We can't do your homework for you here. Providing complete solutions is against the rules. We can only give hints, suggestions to follow, and point out errors or misconceptions.

Drawings have been provided! Suggestions have been provided! Try them!

Haha sorry. It's just a random question I found online and it's been stumping me. Sorry, but even after going through the drawings, I still don't quite see how this can be simplified further. Sure, you've made the middle to capacitors an equivalent one by combining them since they're in series. When you talk about nodes, I'm just slightly confused and don't still exactly understand what you're trying to convey. I've redrawn them but just don't seem to see what you're trying to tell me. It just looks like the current can go through multiple paths in the drawn series and I feel like every time I redraw it is changing the circuit itself. Hence the reason for me asking for more possible images to work with incase I'm drawing/interpreting them wrong.

MathewsMD said:
Haha sorry. It's just a random question I found online and it's been stumping me. Sorry, but even after going through the drawings, I still don't quite see how this can be simplified further. Sure, you've made the middle to capacitors an equivalent one by combining them since they're in series. When you talk about nodes, I'm just slightly confused and don't still exactly understand what you're trying to convey. I've redrawn them but just don't seem to see what you're trying to tell me. It just looks like the current can go through multiple paths in the drawn series and I feel like every time I redraw it is changing the circuit itself. Hence the reason for me asking for more possible images to work with incase I'm drawing/interpreting them wrong.

Perhaps you might want to do a bit of web browsing, looking up the definition of what a node is?

The drawings already provided have specifically identified the nodes in your circuit. From that can you identify which nodes each individual component connects to? Make a list of components and the nodes that they connect to (assume that the equivalent capacitance for the 7 μF and 5 μF capacitors is one of the components). You should see a pattern.

MathewsMD said:
Thank you for the drawing! It definitely clarifies what you meant by the nodes. Now, despite that, I still seem to have some trouble actually drawing the circuit. I've come up with the follow circuit but it is still incorrect. Any further ideas?

Try this -- keep the left and right A and B nodes where they are, and mentally rotate the middle part clockwise 90 degrees. Then redraw the circuit in that new configuration, with all capacitor legs horizontal...

## 1. What is the purpose of finding the total capacitance in a circuit?

Finding the total capacitance in a circuit is important in understanding the overall behavior and performance of the circuit. Capacitance measures the ability of a circuit to store electric charge, so knowing the total capacitance can help determine the amount of charge that can be stored and how it will affect the circuit's operation.

## 2. How do I calculate the total capacitance in a circuit?

To calculate the total capacitance in a circuit, you need to add up the individual capacitance values of all the capacitors in the circuit. This can be done using the formula C = C1 + C2 + C3 + ..., where C is the total capacitance and C1, C2, C3, etc. are the individual capacitance values. Keep in mind that capacitors in parallel add up inversely (1/C = 1/C1 + 1/C2 + 1/C3 + ...), while capacitors in series add up directly (C = C1 + C2 + C3 + ...).

## 3. What are the repercussions of having a high total capacitance in a circuit?

A high total capacitance in a circuit means that the circuit can store a larger amount of electric charge. This can lead to longer charging times and slower discharge rates. It can also cause the circuit to be more sensitive to voltage changes and potentially damage sensitive components.

## 4. How does the placement of capacitors affect the total capacitance in a circuit?

The placement of capacitors in a circuit can affect the total capacitance in different ways. Placing capacitors in parallel will increase the total capacitance, while placing them in series will decrease the total capacitance. Additionally, the proximity of capacitors to other components can also affect their effective capacitance.

## 5. Can the total capacitance in a circuit ever be too high?

Yes, the total capacitance in a circuit can be too high. This can lead to slower charging and discharging times and can affect the overall performance of the circuit. It can also cause damage to sensitive components if the voltage is too high. It is important to carefully consider and calculate the total capacitance needed for a circuit to ensure optimal performance and safety.

Replies
4
Views
2K
Replies
5
Views
698
Replies
8
Views
725
Replies
39
Views
3K
Replies
11
Views
2K
Replies
12
Views
7K
Replies
13
Views
2K
Replies
8
Views
2K
Replies
3
Views
2K
Replies
11
Views
3K