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

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SUMMARY

The voltage Vg in the given electric circuit is determined to be -2V, indicating that the terminals are incorrectly oriented in the diagram. The negative voltage signifies that the positive terminal is actually at a lower potential than the negative terminal, which is a common occurrence in circuit analysis. The calculations performed, including the current ib of 8A and the derived voltage Vx of 2V, confirm the validity of the answer provided in the textbook.

PREREQUISITES
  • Understanding of basic electric circuit theory
  • Familiarity with voltage polarity and its implications
  • Knowledge of current direction and its effect on circuit analysis
  • Ability to interpret circuit diagrams accurately
NEXT STEPS
  • Study the principles of voltage sources and their configurations
  • Learn about Kirchhoff's Voltage Law (KVL) and its applications
  • Explore the concept of controlled sources in electrical circuits
  • Review examples of circuit analysis involving negative voltages
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Electrical engineering students, circuit designers, and anyone involved in analyzing or troubleshooting electric circuits.

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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