Can I find a general solution to this circuit?

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SUMMARY

The discussion focuses on finding the equivalent resistance of a circuit with a variable number of ##R_3## resistors. Participants conclude that there is no general solution for the equivalent resistance that can be expressed simply as a function of ##n##, the number of ##R_3## resistors. Instead, they derive a complex formula involving multiple resistances and suggest approximating the relationship between successive resistances, particularly for large ##n##, similar to solving an infinite ladder circuit. The key takeaway is that while a straightforward formula may not exist, understanding the recursive relationship can simplify calculations.

PREREQUISITES
  • Understanding of equivalent resistance in electrical circuits
  • Familiarity with recursive functions in mathematics
  • Knowledge of ladder circuits and their properties
  • Basic proficiency in circuit analysis techniques
NEXT STEPS
  • Research methods for solving infinite ladder circuits
  • Explore recursive relationships in electrical resistance calculations
  • Study the impact of varying resistor values on equivalent resistance
  • Learn about advanced circuit analysis tools like SPICE simulations
USEFUL FOR

Electrical engineers, physics students, and hobbyists interested in circuit design and analysis will benefit from this discussion, particularly those dealing with complex resistor networks.

Lotto
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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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Google "ladder circuit". You will find methods for dealing with problems like this.
 
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)?
 
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.
 

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