- #1
MsHomework
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Analyzing Electric Circuits: Homework Help
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Homework Help Overview
The discussion revolves around analyzing electric circuits, specifically focusing on applying Kirchhoff's laws and understanding circuit components. Participants are attempting to solve a problem related to resistances and currents in a circuit setup.
Discussion Character
- Exploratory, Conceptual clarification, Problem interpretation, Assumption checking
Approaches and Questions Raised
- Participants discuss calculating resistance using Ohm's law and express confusion about grounding in circuit analysis. Some seek clarification on how to apply Kirchhoff's Current Law (KCL) and the implications of labeling nodes in the circuit.
Discussion Status
There is an ongoing exploration of circuit analysis techniques, with some participants providing hints and guidance on how to approach the problem. However, there is a lack of explicit consensus on the best method to proceed, as confusion persists among participants.
Contextual Notes
Some participants mention constraints from their teacher regarding the use of grounding in their analysis, indicating a potential limitation in the approaches being considered. Additionally, there are references to textbook answers that may not align with the current discussion.
- #2
MsHomework
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Anyone... Please help! I have tried so many times to figure this out but I can't! A hint my teacher gave me is to figure out the R4
- #3
berkeman
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MsHomework said:
Ground the bottom of the voltage source and write the KCL at the node between the left resistor and the right parallel resistors. What does that equation do for you?
- #4
MsHomework
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How do I ground it! I did not learn that...
- #5
berkeman
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MsHomework said:
It just means draw a little ground symbol on that bottom wire, to indicate that you are considering it to be the zero volts potential for the circuit. That way your voltage source output is the value of the source (since it is referenced to zero volts). You could arbitrarily set the bottom of the voltage source to something else like "10 volts", but that just introduces extra complexity into the KCL.
- #6
MsHomework
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64. (a) R4 5 2.50 x 102
I1 = 0.250 A
I2 = 0.150 A
I4 = 0.100 A
(b) V2 = 16.7 V
V3 = 8.30 V
This is the answer from the back of the textbook... Also my teacher said to use the basics aka... I am not suppose to ground!
I1 = 0.250 A
I2 = 0.150 A
I4 = 0.100 A
(b) V2 = 16.7 V
V3 = 8.30 V
This is the answer from the back of the textbook... Also my teacher said to use the basics aka... I am not suppose to ground!
- #7
berkeman
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MsHomework said:
Okay, no problemo. Nothing fancy.
Just label that bottom wire with "0 volts", and write the one KCL equation for the top middle node. Simple!
- #8
MsHomework
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Can you show me step by step, because I still am confused!
- #9
berkeman
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MsHomework said:
No, sorry, that's now how we handle Homework Help at the PF (which you know).
Tell us how to write KCL (Kirchoff's Current Law) equations. Then write the KCL for the node in the middle of the upper branch as I mentioned several times already.
http://www.wiziq.com/tutorial/32583-Solving-problems-using-Kirchoff-s-Law-I
.
- #10
MsHomework
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Just a quick question, How come you have to put 0 volts at the bottom in the parallel...
- #11
berkeman
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MsHomework said:
With the KCL, you will write the sum of all currents leaving that central node = 0 (amps or milliamps). When you write the currents as V/R for each branch, the delta-V is the voltage at the node minus the voltage at the node on the other side of the resistance. If you label the bottom wire as 0 volts, then that second voltage in the subtraction goes away in the equation (because it is 0). It's mostly a convenience thing for writing the KCL equations -- pick a logical node to label as 0 volts before starting to write out the KCL equation(s).
If a node is already labeled with a ground symbol in a schematic, you automatically take that node as being at 0 volts.
Can you take a cut at writing the KCL at that node now?
- #12
MsHomework
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I am sorry, but I personally feel more confused! I don`t feel that you are helping me as much. Thank you for trying to help!
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