Understanding Conventional vs Electron Flow in Node Voltage Analysis

In summary, the question asks the person to find I_o and V_o. The person forgot to mention that voltage is constant in a parallel circuit, so they solved for V using voltage and current.
  • #1
LocationX
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The question asks me to find [tex]i_o[/tex] and [tex]V_o[/tex]

I'm not sure how to do it since I don't know which way the current goes on the 8 ohms resistor. any ideas?
 

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  • #2
Current enters from the negative side and exits from the positives. Current always flows from the negative side of the battery (electron convention).

I wish I could help you more, but I can't see the posted image.
 
  • #3
that's not really true because my book has examples that have current going into the positive side. All that does is switch the voltage from negative to positive, or vise versa,
 
  • #4
The attachment is still awaiting approval. Depending on how complicated the circuit is, you don't know what direction the current is going until you solve the circuit. You pick a direction to set up your equation (and make sure to label you circuit so you remember which direction you picked). If you picked right, the current will be positive. If you picked wrong, the current will be negative.

You didn't explain what you're trying to do, so without seeing the attachment, it's hard to give a good answer. In general, for node voltage analysis, you can set all the currents as leaving the node (obviously at least one has to be going into the node, but that illustrates just how insignificant the initial direction you pick is). If using mesh current, just set all the currents to go either clockwise or counter-clockwise - doesn't matter which, but things are generally easier to keep straight if all the directions are the same.
 
  • #5
okay, the image is up, any ideas oh how to find I and v?
 
  • #6
Node voltage analysis. Put your ground on the bottom and you only have one node to solve for (Node A). Set all your currents coming out of the top node (this means the current source is giving you -6 Amps).

You need to make a substitution for Io in the dependent source. If you know ohm's law, you should be able to figure out what to substitute in place of Io.

Setting up your equation is the hard part. If you set it up right, you only have one variable to solve for. You have a parallel circuit, so vo is easy once you figure out the voltage at Node A.
 
  • #7
ah! okay, forgot that voltage was constant in a parallel circut. I just set the current to add up to 6A and solve for voltage...

V/2+V/8+V/8=6

so V=8
thanks
 
  • #8
LocationX said:
that's not really true because my book has examples that have current going into the positive side. All that does is switch the voltage from negative to positive, or vise versa,

Current is the flow of electrons through a conductor. And as we know electrons have a negative(-) charge. This would make perfect sense to have the electrons start off from the negative terminal of the power source and end up at the positive ternimal. So I really can't understand why some books have current flowing from the positive ternimal. That isn't really happening right? I know that we have two conventions used. I too was taught using the conventional method, but I really perfere the electron convention. But I still fail to see why we have two. Anyone care to explain?
 

1. What is node voltage analysis?

Node voltage analysis is a method used to analyze electrical circuits and determine the voltage of each node in the circuit. It is based on Kirchhoff's Current Law and Ohm's Law.

2. How is node voltage analysis performed?

To perform node voltage analysis, you first need to identify all the nodes in the circuit and label them. Then, create equations for each node using Kirchhoff's Current Law and Ohm's Law. Finally, solve the equations to find the voltage of each node.

3. What are the advantages of using node voltage analysis?

Node voltage analysis is a systematic and efficient method for analyzing circuits. It allows for easy identification of unknown voltages and can be applied to both linear and nonlinear circuits.

4. Are there any limitations to node voltage analysis?

Node voltage analysis can only be used for circuits with independent voltage sources. It also assumes that the circuit is in steady-state conditions and does not take into account the effects of inductance and capacitance.

5. Can node voltage analysis be used for circuits with multiple voltage sources?

Yes, node voltage analysis can be used for circuits with multiple voltage sources. In these cases, a superposition theorem can be used to analyze the circuit by considering each voltage source separately.

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