Solve the Circuit: Find R1-R7 to Calculate A to B Resistance

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Homework Help Overview

The discussion revolves around calculating the equivalent resistance in a circuit with multiple resistors labeled R1 through R7. The original poster presents a circuit diagram and specifies the resistance values for each resistor, seeking assistance in determining the total resistance between points A and B.

Discussion Character

  • Exploratory, Problem interpretation, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to calculate the total resistance by identifying resistors in parallel and series but expresses confusion about the correct arrangement of resistors. Some participants suggest starting with specific combinations of resistors and working towards the overall total, while others question the placement of combined resistances within the circuit.

Discussion Status

Participants are actively engaging in clarifying the arrangement of resistors and the process for calculating equivalent resistance. There is a mix of interpretations regarding the placement of combined resistances, and while some guidance has been offered, there is no explicit consensus on the correct approach yet.

Contextual Notes

The original poster is working under the constraints of a homework assignment, which may impose specific methods or expectations for solving the problem. There is an ongoing discussion about the assumptions related to the circuit configuration and the relationships between the resistors.

spoonthrower
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AxxxxxxR1xxxxxxxxxxxxxR2xxxxxxxxR3xxxxxxx
ooooooooooooooXoooooooooXooooooooooox
ooooooooooooooXoooooooooXooooooooooox
ooooooooooooooR4ooooooooR5oooooooooR6
ooooooooooooooXoooooooooXooooooooooox
BxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxR7xxxxxx

For the circuit above the x's represent the wire and R represents the resistance. o's just fill in open space - ignore them. Find the equivalent resistance between points A and B.
R1=5 ohms
R2=4 ohms
R3=6 ohms
R4=10 ohms
R5=8 ohms
R6=7 ohms
R7=3 ohms

So i need to find the total resistance in the circuit. I know that R4,5, and 6 are in parallel so their resistance should add up like 1/(1/10+1/8+1/7) to give 2.72 ohms. so the rest of the resistances are in series so you just add them all up right? when i add them all together with 2.72 ohms, I am not getting the right answer. What am i doing wrong? please help. thanks.
 
Last edited:
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R3, 6 and 7 are in series. Start by trying to calculate their combined resistance first.
 
Adding to what andrevdh suggests, a good place to start is the at the end of the circuit. After you've found a combined resistance Rcr for those andrevdh described, you can then work your way towards the right. Notice R5 is now in parallel with your new combined resistance Rcr; you can combine these two to get a new combined resistance. Can you see the process?
 
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i do not see how Rcr is in parallel with R5 at all. If it is in parallel with R5 that means that when u add Rcr up, it would have to be at the R6 location. Why can't u place the new Rcr at the R3 location. i am really confused.
 
spoonthrower said:
i do not see how Rcr is in parallel with R5 at all. If it is in parallel with R5 that means that when u add Rcr up, it would have to be at the R6 location. Why can't u place the new Rcr at the R3 location. i am really confused.

You could put the combined resistance Rcr (combined from R3, R6 and R7) anywhere in the branch at the extreme right. You could place it wheer R3 is or wher R6 is or where R7 is. In *all* three cases, Rcr is still in parallel with R5
 
got it. thank you so much.
 

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