- #1
SOLVING[Series-Parallel Circuits
- Context: Engineering
- Thread starter Slashz
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Discussion Overview
The discussion revolves around solving a circuit problem involving series and parallel resistors, specifically determining the total voltage required for a specified current (I3 = 1A) through one of the resistors (R3). The conversation includes attempts at applying relevant electrical laws and equations.
Discussion Character
- Homework-related
- Mathematical reasoning
- Technical explanation
- Debate/contested
Main Points Raised
- Participants question the identification of I3 and its relation to R3.
- Some participants emphasize the necessity of relevant equations for solving circuit problems.
- One participant provides a calculation for total resistance (Rt) but is challenged on its relevance given the circuit configuration.
- There is a mention of Kirchhoff's laws (KVL and KCL) as important concepts for solving the problem.
- One participant confirms the calculation of voltage across R3 (V3) as correct, while also discussing the implications for current through R4.
- Another participant suggests using the voltage divider principle as a quicker method, contrasting it with the more instructive approach of Kirchhoff's laws.
Areas of Agreement / Disagreement
Participants express differing views on the best approach to solve the circuit problem, with some favoring Kirchhoff's laws for their educational value while others suggest alternative methods. There is no consensus on the correct application of the calculations or the relevance of certain steps taken.
Contextual Notes
There are unresolved aspects regarding the circuit configuration, particularly the role of R1 in relation to the voltage source and the overall circuit analysis. Some calculations and assumptions made by participants may depend on specific interpretations of the circuit layout.
- #2
gneill
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Slashz said:
1. You haven't identified where I3 is (Is it the current through R3?).
2. There must be relevant equations! Otherwise, how would such problems get solved?
3. You need to provide some attempt at a solution, or at least some discussion of what you've already tried.
- #3
Slashz
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ohh sorry so this is my attempt.
1. You haven't identified where I3 is (Is it the current through R3?).Yes
2. There must be relevant equations! Otherwise, how would such problems get solved?
http://en.wikipedia.org/wiki/Ohm's_law
3. You need to provide some attempt at a solution, or at least some discussion of what you've already tried.
Rt=R1+R2+R34
Rt=10+13+2
Rt=25
I3=1
V3=I3R3
V3=1(6)
V3=6
I4=I2-I3
I4=I2-1
I2-I4=1
1. You haven't identified where I3 is (Is it the current through R3?).Yes
2. There must be relevant equations! Otherwise, how would such problems get solved?
http://en.wikipedia.org/wiki/Ohm's_law
3. You need to provide some attempt at a solution, or at least some discussion of what you've already tried.
Rt=R1+R2+R34
Rt=10+13+2
Rt=25
I3=1
V3=I3R3
V3=1(6)
V3=6
I4=I2-I3
I4=I2-1
I2-I4=1
- #4
gneill
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Have you not learned about Kirchhoff's laws? KVL? KCL?Slashz said:
Note that R1 is in parallel with the voltage source (let's call it V) . If the voltage source is ideal then the potential with respect to ground at the node where R1 and R2 meet is fixed by V regardless of the value of R1. So we can expect that the value of R1 will not play a role in determining V.
It's not clear why you calculated Rt above, or what it represents, since R1 is not in series with R2 and R3||R4.
Since you've determined the voltage that appears across R3 above, what can you say about the current through R4?I3=1
V3=I3R3
V3=1(6)
V3=6 <--- Okay, good!
I4=I2-I3
I4=I2-1
I2-I4=1 <--- Okay! (Note that you've used KCL)
- #5
Curious3141
Homework Helper
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The quickest way to do it is to use the voltage divider principle. But doing it with Kirchoff's laws is the most instructive way and teaches basic principles well. 
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