Finding 2 Unknown Currents and Voltage with Resistance

In summary, the problem is trying to find the power of a 6Ω resistor in parallel with two other resistors.
  • #1
RainbowTuba
3
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.
 
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  • #2
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?
 
  • #3
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?
 
  • #4
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...
 
  • #5
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...
 

FAQ: Finding 2 Unknown Currents and Voltage with Resistance

1. What is the purpose of finding two unknown currents and voltage with resistance?

The purpose of finding two unknown currents and voltage with resistance is to determine the values of the current and voltage in a circuit, which can then be used to analyze and understand the behavior of the circuit. This information can also be used to troubleshoot any issues or make necessary adjustments to the circuit.

2. How do you determine the resistance of a circuit?

The resistance of a circuit can be determined by using Ohm's law, which states that resistance (R) is equal to the voltage (V) divided by the current (I). So, R = V/I. This equation can be rearranged to solve for any of the variables, depending on which values are known.

3. What equipment is needed to find two unknown currents and voltage with resistance?

To find two unknown currents and voltage with resistance, you will need a power source, a resistor, a voltmeter, and an ammeter. The power source provides the voltage in the circuit, the resistor creates the resistance, and the voltmeter and ammeter measure the voltage and current, respectively.

4. Can the values of the unknown currents and voltage be found without using a resistor?

No, a resistor is necessary to create a known resistance in the circuit, which is needed to solve for the unknown currents and voltage. Without a resistor, the circuit would have an infinite resistance and no current would flow, making it impossible to find the values of the unknowns.

5. Are there any limitations to using this method to find unknown currents and voltage with resistance?

Yes, there are some limitations to this method. It assumes that the circuit is linear and follows Ohm's law, which may not always be the case. It also does not take into account the effects of temperature, which can alter the resistance of certain materials. Additionally, using a voltmeter and ammeter can introduce some error into the measurements, so the values obtained may not be completely accurate.

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