Calculate resistance for this diagram

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Homework Help Overview

The discussion revolves around calculating the equivalent resistance in a circuit diagram involving resistors. Participants are examining the configuration of the resistors and the implications of a horizontal line in the diagram.

Discussion Character

  • Conceptual clarification, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants explore whether the resistors are in parallel and discuss the significance of the horizontal line in the diagram. There are attempts to apply the formula for resistors in parallel, and questions arise about the behavior of current in the circuit.

Discussion Status

The discussion is active, with participants questioning assumptions about the circuit configuration and providing insights into the implications of having a zero-ohm path. There is no explicit consensus on the final equivalent resistance, but several lines of reasoning are being explored.

Contextual Notes

Participants are navigating the implications of the circuit layout and the presence of a wire, which is treated as a zero-ohm resistor, affecting current flow. The original poster's initial assumption about the resistors being in parallel is challenged.

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Homework Statement



Calculate the equivalent resistance. (Diagram attached)

Homework Equations



1/Rp=(1/R1)+(1/R2)

The Attempt at a Solution



1/25+1/5=1/Rp
Rp=4.17 ohm

is it correct?
 

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No. Are those resistors in parallel? Hint: What's the significance of the horizontal line in the middle of the diagram?
 
Doc Al said:
No. Are those resistors in parallel? Hint: What's the significance of the horizontal line in the middle of the diagram?

No! They are not. There are 2 paths generated, one through both the resistors and the other through only the 5 ohm resistor. So I arrived at the result:
(1/(5+20))+(1/5)=1/Rp
 
Those resistors are not in parallel, but I don't know how you got that new result (which looks like an application of the resistors in parallel formula). Please attempt to answer my other question:

Doc Al said:
What's the significance of the horizontal line in the middle of the diagram?
 
Doc Al said:
Those resistors are not in parallel, but I don't know how you got that new result (which looks like an application of the resistors in parallel formula). Please attempt to answer my other question:

well, it provides a no resistor path for current. So is the answer 5 ohm?
 
Yes! You can treat the wire as being a 0 ohm resistor in parallel with the 20 ohm resistor. Use the formula for parallel resistors to find the equivalent resistance of those two = 0.
 
Doc Al said:
Yes! You can treat the wire as being a 0 ohm resistor in parallel with the 20 ohm resistor. Use the formula for parallel resistors to find the equivalent resistance of those two = 0.

But will you please tell me why won't the current divide at the first branch (as my teacher told me)?
 
Since one of those branches has zero resistance, all of the current "chooses" that branch.
 
Thanx!
 

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