Circuit with two voltage sources (Kirchoff Rules)

AI Thread Summary
The discussion revolves around solving a circuit problem using Kirchhoff's Rules, with specific resistor values and voltage provided. The user initially calculated the currents I1, I2, and I3 but received incorrect feedback from Web Assign, despite multiple attempts. A key oversight was identified regarding the connection of R2 to a 3-ohm resistor in series, which was crucial for accurate calculations. The user expressed surprise at missing this detail, and a fellow participant acknowledged the correction. This highlights the importance of careful analysis in circuit problems to ensure all components are correctly accounted for.
XianForce
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Homework Statement


The circuit shown in the figure below is connected for 3.10 min. (Assume R1 = 7.90 Ω, R2 = 2.60 Ω, and V = 16.0 V.)
28-p-021-alt.gif

The circuit shown in the figure below is connected for 3.10 min. (Assume R1 = 7.90 Ω, R2 = 2.60 Ω, and V = 16.0 V.)


Homework Equations


Kirchoff's Rules
V = IR


The Attempt at a Solution


So naming the current in the left segment I1 downwards, the current in the middle section I2 downwards, and the current in the right most section I3 upwards, I find from the junction rule that I1 + I2 = I3. Then using the current rule, I find that -16 +7.9 * I1 + 2.6 * I3 = 0. Substituting in I3 as I1 + I2, and then solving for I1 I find that I1 = (16 - 2.6I2) / 10.5 . Using the current rule again, I find that -4 + 7.9 * I1 - 6.0 * I2 = 0 and so I substitute for I1 and then solve for I2 to find that I2 = 1.0103. Then use that value back in other equations to find that I1 = 1.2736 Amperes downward, I2 = 1.0103 Amperes downward, and I3 = 2.2839 Amperes Upward.

Web Assign keeps saying these values are wrong and I have reworked these problems several times and keep getting the same answers.
 
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XianForce said:

Homework Statement


The circuit shown in the figure below is connected for 3.10 min. (Assume R1 = 7.90 Ω, R2 = 2.60 Ω, and V = 16.0 V.)
28-p-021-alt.gif

The circuit shown in the figure below is connected for 3.10 min. (Assume R1 = 7.90 Ω, R2 = 2.60 Ω, and V = 16.0 V.)

Homework Equations


Kirchoff's Rules
V = IR

The Attempt at a Solution


So naming the current in the left segment I1 downwards, the current in the middle section I2 downwards, and the current in the right most section I3 upwards, I find from the junction rule that I1 + I2 = I3. Then using the current rule, I find that -16 +7.9 * I1 + 2.6 * I3 = 0.

R2 is connected to a 3 ohm resistor in series.

ehild
 
I cannot believe I missed that. Thank you!
 
XianForce said:
I cannot believe I missed that. Thank you!

You are welcome.:smile:

ehild
 

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