Determine the current in this circuit

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    Circuit Current
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Discussion Overview

The discussion revolves around determining the current in a circuit involving multiple resistors. Participants are analyzing circuit diagrams to clarify the connections between resistors and the power supply, focusing on the implications of these connections for calculating current.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses uncertainty about how to determine the direction of current flow in the circuit.
  • Another participant provides an updated circuit diagram to clarify the connections.
  • A participant points out discrepancies between the original and modified circuit diagrams, emphasizing that the connections of the resistors are not the same in both cases.
  • One participant suggests looking up information about nodes in circuits, indicating that understanding this concept may help clarify the situation.
  • Another participant reiterates that the connections of the 13 Ohm resistor differ between the original and the modified diagrams, which affects the circuit's configuration.

Areas of Agreement / Disagreement

Participants appear to agree on the importance of accurately representing the circuit connections, but there is disagreement regarding the interpretation of the diagrams and how they affect the calculation of current.

Contextual Notes

There are unresolved assumptions about the definitions of nodes and how they relate to the circuit's behavior. The discussion does not clarify the mathematical steps needed to determine the current.

tensor0910
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Homework Statement



Find the current Ig[/B]
upload_2018-2-26_10-23-18.png


Homework Equations


[/B]
V1 = R1/(R1 + R2) * Vs

1/Rtotal = 1/R1 + 1/R2 + 1/R3...example

The Attempt at a Solution


I know what I did wrong, but I don't know how to avoid it. Here's what I mean.

upload_2018-2-26_10-29-1.png


How do you know which way its suppose to be?
 

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Last edited by a moderator:
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I added onto the old picture. Hopefully this clears things up.

upload_2018-2-26_10-47-7.png
 

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In your "How do I know it's this...and not this" pictures, look at the resistor connections and they are obviously not the same. In the original circuit, the 5 Ohm and the 20 Ohm resistors are in parallel. One end of them is connected to the 6 Ohm resistor and the other end is connected to both the 13 Ohm resistor and the negative of the power supply. This is exactly the same connections as in your "How do i know it's this" picture. But in your "and not this" picture, the ends that are connected to the 6 Ohm resistor are now connected to the negative of the power supply. It's just not the same connections.
 
Look up about how to determine what a Node is. Wikipedia has some pretty good info on this. I'd put more now, but I'm on my phone.
 
In original and in the left hand diagram the 13R has one end connected to the -ve side of the voltage source. In the right hand diagram is doesn't. So the right hand ("and not this") circuit is different to the original.
 
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