Can I find a general solution to this circuit?

In summary, the conversation discusses finding an equivalent resistance for a circuit with multiple ##R_3## resistors. The speaker mentions using a general solution and suggests looking up "ladder circuit" methods. They also mention a relationship between the resistance of the circuit and the number of ##R_3## resistors, making it easier to solve for large values of ##n##.
  • #1
Lotto
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16
Thread moved from the technical forums to the schoolwork forums
TL;DR Summary: I have to find an equivalent resistance of the circuit below, dependent on the amount of ##R_3## - resistors.

Here is the circuit:
circuit2.jpg

I think there is no general solution. When I want to calculate it, I have to do ##((((R_1+2R_2)^{-1}+{R_3}^{-1})^{-1}+2R_2)^{-1}+{R_3}^{-1})^{-1}...##, so it is kind of crazy. Is there any general solution dependent on the amount of ##R_3## - resistors ##n##? So something like ##R_{\mathrm {eq} _n}=....##.
 
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  • #2
Google "ladder circuit". You will find methods for dealing with problems like this.
 
  • #3
Lotto said:
TL;DR Summary: I have to find an equivalent resistance of the circuit below, dependent on the amount of ##R_3## - resistors.

Here is the circuit:
View attachment 326155
I think there is no general solution. When I want to calculate it, I have to do ##((((R_1+2R_2)^{-1}+{R_3}^{-1})^{-1}+2R_2)^{-1}+{R_3}^{-1})^{-1}...##, so it is kind of crazy. Is there any general solution dependent on the amount of ##R_3## - resistors ##n##? So something like ##R_{\mathrm {eq} _n}=....##.
My first step would be to leave out the two R1s. Those can be put back in later.
The resistance of the remaining system is a function R(n). Can you figure out the relationship between R(n) and R(n+1)?
 
  • #4
haruspex said:
My first step would be to leave out the two R1s. Those can be put back in later.
The resistance of the remaining system is a function R(n). Can you figure out the relationship between R(n) and R(n+1)?
Yes, I did it and I made an approximation when ##n## is big, so we can say that ##R_n \approx R_{n-1}##, similary as when we solve an infinite ladder circuit. Then it was easy to solve.
 

FAQ: Can I find a general solution to this circuit?

What is a general solution in the context of electrical circuits?

A general solution in the context of electrical circuits refers to a comprehensive mathematical expression or set of expressions that describe the behavior of the circuit's voltages and currents over time. This includes solutions to differential equations that account for all possible initial conditions and external inputs.

What methods can be used to find the general solution to a circuit?

Several methods can be used to find the general solution to a circuit, including Kirchhoff's laws (KVL and KCL), mesh and nodal analysis, Thevenin's and Norton's theorems, and the use of Laplace transforms. These methods help to set up and solve the necessary differential equations that describe the circuit's behavior.

Can SPICE simulations provide a general solution to a circuit?

SPICE simulations can provide numerical solutions to specific instances of a circuit's behavior under given conditions. While they are extremely useful for practical analysis and design, they do not provide a general analytical solution. SPICE results are typically used to validate the behavior predicted by general solutions.

What are the challenges in finding a general solution to complex circuits?

Finding a general solution to complex circuits can be challenging due to the presence of multiple components with different characteristics (resistors, capacitors, inductors, etc.), non-linear elements, and the need to solve higher-order differential equations. Additionally, the interdependencies between various circuit elements can make the mathematical analysis quite intricate.

Is it always possible to find a general solution to any circuit?

While it is often possible to find a general solution to many circuits, there are cases where it may be impractical or extremely difficult, especially for highly complex or non-linear circuits. In such cases, numerical methods, approximations, and simulations are commonly used to analyze and predict circuit behavior.

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