Kirchhoff's laws question circuit?

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Homework Help Overview

The discussion revolves around a circuit analysis problem involving Kirchhoff's laws. The original poster is attempting to find the current i1 and the resistance R in a given circuit configuration, which includes resistors of 2 Ohm, 4 Ohm, and 8 Ohm.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss applying Kirchhoff's laws and current division to analyze the circuit. There are attempts to determine the voltage across the 4 Ohm resistor and the current through the 8 Ohm resistor. Questions arise about the relationship between the currents in different branches of the circuit.

Discussion Status

Participants are actively engaging with the problem, exploring various interpretations of the circuit's behavior. Some guidance has been offered regarding the application of nodal analysis, and there is a recognition of the need to clarify the currents at specific nodes.

Contextual Notes

There is uncertainty regarding the potential at a specific node, which is noted as a factor that could aid in determining the current through the 2 Ohm resistor. The original poster expresses a desire to explore the problem further.

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Homework Statement



I have the circuit in the figure.I have to find i1 and R

Homework Equations



I am thinking about applying the division of the current and any of the K's laws but I don't know where to start.Can you pleas give me a hint?

The Attempt at a Solution


I tried to find the voltage in the 4 Ohm resistance and it is 8 Volt.Since 4 oHm is in parallel with 8 Ohm ,then their voltage equals.This is how far I have got.
http://i.imgur.com/FoQmlFl.jpg?1?3770
 
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Elaia06 said:
I tried to find the voltage in the 4 Ohm resistance and it is 8 Volt.Since 4 oHm is in parallel with 8 Ohm ,then their voltage equals.This is how far I have got.

Find the current through the 8Ω resistor. What new current can you label on the diagram?
 
It's 1 A.Does that mean that the current through R is 3A?
 
Elaia06 said:
It's 1 A.Does that mean that the current through R is 3A?

Yes. Where does the 3A come from (what other current must be 3A)?
 
The one running through 2 Ohm?
 
Elaia06 said:
The one running through 2 Ohm?

Yes and no. Certainly the 3 A flows there, but i1 also flows through that resistor. Can you place the 3 A on the appropriate wire leading from the node? Any ideas what you might do with that knowledge?
 
I want to find the current in 2 Ohm so I can apply the K's law in the nod...but I don't know how
 
Elaia06 said:
I want to find the current in 2 Ohm so I can apply the K's law in the nod...but I don't know how

Suppose that you happened to know the potential of that node. Would you be able to find that current then?
 
yes.This sounds like a puzzle.I'll have a look at it myself later.Thank you anyway.
 
  • #10
Elaia06 said:
yes.This sounds like a puzzle.I'll have a look at it myself later.Thank you anyway.

Good idea :smile:

As a hint, consider applying nodal analysis at the node (KCL with a bit of KVL thrown in ) :wink:
 
  • #11
O mi god that's what I want thinking! Thanks a lot mate!
 

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