Circuits: Solve Using Nodal and mesh Analysis

Click For Summary
The discussion focuses on solving a circuit using nodal and mesh analysis, specifically addressing the application of Kirchhoff's Current Law (KCL) and Kirchhoff's Voltage Law (KVL). The user initially expresses confusion about the configuration of resistors R1, R2, and R3, questioning whether they are in parallel. It is clarified that these resistors are not in parallel since they do not share the same voltage across their terminals. The user successfully formulates node voltage equations for nodes A, B, and C, indicating progress in their understanding of the circuit analysis. The conversation emphasizes the importance of correctly identifying resistor configurations to apply nodal analysis effectively.
Saladsamurai
Messages
3,009
Reaction score
7

Homework Statement


prob224.jpg

fig224.jpg




Homework Equations


KCL & KVL:


The Attempt at a Solution



Ok folks :smile: I am not sure where to go from here. Someone suggested changing the 144V to its Thevenin equivalent, which I have done below. I know that I am supposed to apply KCL at each node A,B, and C. And then I represent each current in terms of voltages. Now I am a little confused as to how to proceed.

I am trying got convince myself that R1, R2, and R3 are in parallel because their leads are all connected, but I am not sure yet. The voltage drop across R1 is definitely just VA since I can pass from A across the resistor and directly to ground. But for R2 and R3, I feel like the voltages at B and C need to be considered.

Any thoughts?


mysol.jpg
 
Physics news on Phys.org
I think you meant to say that you've changed the voltage supply and its series resistance to its Norton equivalent.

Also, one leg in common does not a parallel connection make; R1, R2, and R3 are not in parallel.

With the network as shown in your second diagram, you are in a position to write the node voltage equations by inspection.
 
gneill said:
I think you meant to say that you've changed the voltage supply and its series resistance to its Norton equivalent.

Also, one leg in common does not a parallel connection make; R1, R2, and R3 are not in parallel.

With the network as shown in your second diagram, you are in a position to write the node voltage equations by inspection.

So they are not in parallel because they do not share the same voltage, correct?

I think I have it now:

Node A:

48 - V_A/3 - (V_B - V_A)/4 - (V_C - V_A)/4 = 0

Node B:

(V_B - V_A)/4 - (V_C - V_B)/3 - V_B/2 = 0

Node C:

-V_C/12 + (V_C - V_B)/3 + (V_C - V_A)/4 = 0

Now I need to move forward to the mesh analysis.
 
For components to be in parallel, both ends of each need to be directly connected to each other.

It looks like you're on the right track. Keep up the good work!
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

Similar threads

  • · Replies 12 ·
Replies
12
Views
2K
Replies
5
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 1 ·
Replies
1
Views
796
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 18 ·
Replies
18
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
Replies
7
Views
2K
Replies
13
Views
2K