- #1
Problem finding the direction of current (electricity)
- Thread starter AXiMe
- Start date
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- Current Direction Electricity
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Homework Help Overview
The discussion revolves around determining the direction of current in an electrical circuit, specifically focusing on the currents I1, I2, and I3. Participants are exploring concepts related to Kirchhoff's Voltage Law (KVL) and current direction assumptions.
Discussion Character
- Exploratory, Assumption checking, Conceptual clarification
Approaches and Questions Raised
- Participants discuss the relationship between the currents using the equation I1 = I2 + I3 and express confusion regarding the direction of I3. Some mention the possibility of I3 being negative, indicating a reversal of the assumed direction.
Discussion Status
There is ongoing exploration of the assumptions made regarding current direction. Some participants have provided insights into the self-correcting nature of KVL when negative values are encountered, but there is no explicit consensus on the understanding of why negative values arise.
Contextual Notes
Participants are navigating the implications of their initial assumptions about current direction and the effects of solving KVL equations. There is a mention of differing approaches, such as using KCL, which may not present the same issues with assumed directions.
- #2
berkeman
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AXiMe said:
When you solve for the currents, it may well turn out that I3 turns out to have a negative sign, which would mean that it actually flows the other way. When starting out KVL loop equations, you just assume some direction for each branch current, and then solve. If some of them turn out negative, you can go back and reverse the arrow and change the answer to positive. No big deal.
Welcome to the PF, BTW!
- #3
AXiMe
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Thanks! Albeit, I still don't understand why it would come out negative, even though the answer says so...
- #4
berkeman
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AXiMe said:
I didn't work through the problem you posted, but this is just a general part of using KVL to solve circuits. You have to assume some direction for the current in each leg before you can solve the equations. Once you solve the equations, if the current comes out with a negative sign, then that just means that the initial guess at current direction was wrong. No big deal, the process is self-correcting.
When you use KCL equations, you don't have this issue, because you just label nodes with some voltages like V_1, V_2, etc. When you solve the simultaneous equations, you get whether they are positive or negative (or changing) voltages as part of the solution.
- #5
berkeman
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AXiMe said:
Oh, and don't call me Albeit. I prefer Shirley.
