Electric Circuits: Find Vg & Why is it -2V?

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Homework Help Overview

The discussion revolves around an electric circuit problem where participants are trying to determine the value of Vg for the circuit to be valid, noting that the answer is -2V. The original poster questions why the voltage is negative.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss the implications of the negative voltage, with some suggesting that the terminals may be drawn incorrectly. There are also questions about the direction of current and its effect on the calculations.

Discussion Status

The discussion is active, with participants exploring different interpretations of the circuit's configuration and the implications of the voltage sign. Some guidance has been provided regarding the direction of current and its relationship to the voltage calculations.

Contextual Notes

There are references to a provided answer key, which suggests a potential constraint on the discussion, as well as a focus on the defined direction of current in the circuit.

sevag00
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Homework Statement



Hi. I have an electric circuit attached below. The question is to find the value Vg in order for the interconnection to be valid. The answer is -2V.
My question is, why is the voltage minus?
 

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You did the calculation - if you read the diagram correctly you set the [+] terminal to have a higher voltage than the [-] terminal. The minus sign means that the terminals are drawn the wrong way around.
As to "why", you may have done the calculation wrong or maybe that's just the way the physics works out for that configuration.
 
Simon Bridge said:
You did the calculation - if you read the diagram correctly you set the [+] terminal to have a higher voltage than the [-] terminal. The minus sign means that the terminals are drawn the wrong way around.
As to "why", you may have done the calculation wrong or maybe that's just the way the physics works out for that configuration.
I doubt there is miscalculation, because the book had already given the answer key.
 
sevag00 said:

Homework Statement



Hi. I have an electric circuit attached below. The question is to find the value Vg in order for the interconnection to be valid. The answer is -2V.
My question is, why is the voltage minus?

Show how you would determine the potential of the controlled source on the left.
 
ib=8A, Vx= ib/4 = 8/4=2V
 
Last edited:
sevag00 said:
ib=8A, Vx= ib/4 = 8/4=2V

Check the defined direction of ib. Is the 8 A source really driving current in the direction indicated?
 
Oh. You mean they are in opposite direction. So the current ib is negative, right?
 
sevag00 said:
Oh. You mean they are in opposite direction. So the current ib is negative, right?

Right.
 
Good. Thanks for the help.
 

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