Finding 2 Unknown Currents and Voltage with Resistance

AI Thread Summary
The discussion revolves around solving for voltage (V), currents (I1, I2), and power in a circuit with known resistances and current sources. The initial approach using Kirchhoff's Current Law (KCL) was deemed incomplete, leading to confusion about combining the current sources. Participants clarified that the two current sources do not add directly due to their opposing directions, and suggested finding the net current driving through the resistors. The equivalent resistance was identified as 2Ω, which helps in calculating the output voltage. The conversation highlights the importance of correctly setting up equations and understanding circuit behavior to solve for unknowns effectively.
RainbowTuba
Messages
3
Reaction score
0

Homework Statement


Find V, I1, I2 and the power of the 6Ω resistor:
BbnJDSD.jpg

Known:
R1=6Ω
R2=3Ω
Iknown1=8
Iknown2=2
RTotal=2Ω

Homework Equations


P=V2/R
P=IV
V=IR

The Attempt at a Solution


To be honest, I've been staring at the problem for hours not knowing where to begin. I thought I'd start with a KCL equation to find I1 and I2, but I'm left with too many unknowns to continue on.
I tried using a point above the 6Ω resistor as a node to find the KCL: Using V1 as my voltage at the node.
-8 -I1+I2=0
= (V1-V)/3 = 8+(V1-V)/6
= V1=V+48
But I don't believe I'm setting up the equation right in the first place.
 
Physics news on Phys.org
RainbowTuba said:

Homework Statement


Find V, I1, I2 and the power of the 6Ω resistor:
BbnJDSD.jpg

Known:
R1=6Ω
R2=3Ω
Iknown1=8
Iknown2=2
RTotal=2Ω

Homework Equations


P=V2/R
P=IV
V=IR

The Attempt at a Solution


To be honest, I've been staring at the problem for hours not knowing where to begin. I thought I'd start with a KCL equation to find I1 and I2, but I'm left with too many unknowns to continue on.
I tried using a point above the 6Ω resistor as a node to find the KCL: Using V1 as my voltage at the node.
-8 -I1+I2=0
= (V1-V)/3 = 8+(V1-V)/6
= V1=V+48
But I don't believe I'm setting up the equation right in the first place.

Welcome to the PF.

This equation of yours: -8 -I1+I2=0 is incomplete.

Instead, what can you say when you have 2 current sources in parallel? What is the net current source that drives the parallel resistor combination?
 
berkeman said:
Welcome to the PF.

This equation of yours: -8 -I1+I2=0 is incomplete.

Instead, what can you say when you have 2 current sources in parallel? What is the net current source that drives the parallel resistor combination?

So I can find an equivalent resistance of the two, which would equal 2, and the net current source would be 10A.

I figured since the unknown current is a factor, simplifying the circuit would combine the two, is this incorrect?

So would I use
-2-8 -I1+I2=0
instead?
 
RainbowTuba said:
So I can find an equivalent resistance of the two, which would equal 2, and the net current source would be 10A.

I figured since the unknown current is a factor, simplifying the circuit would combine the two, is this incorrect?

So would I use
-2-8 -I1+I2=0
instead?

The two current sources drive their current through the resistors in opposite directions, so they don't add.

And once you have the correct net current driving through the resistors, combine the two resistors into the equivalent resistance to find Vout. Then use Vout and the individual resistance values to...
 
berkeman said:
The two current sources drive their current through the resistors in opposite directions, so they don't add.

And once you have the correct net current driving through the resistors, combine the two resistors into the equivalent resistance to find Vout. Then use Vout and the individual resistance values to...

Yes they do, so instead of -10 it would be -6. Combining the resistance and capacitance would lessen the unknowns by one, so R=2 and I is our unknown

So:
-6 = I
which would make V=IR=(-6)2=-12, my assumed direction of I was wrong, so V=12, am I on the right track?

I feel like I did something wrong...
 

Similar threads

Replies
26
Views
3K
Replies
1
Views
3K
Replies
4
Views
2K
Replies
13
Views
4K
Replies
17
Views
2K
Replies
7
Views
2K
Back
Top