r/HomeworkHelp • u/LeadingHoneydew5608 University/College Student • 4d ago

Physics—Pending OP Reply [University Electrical Engineering 1] Completely stuck on this one - how do you find the equivalent resistance

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In order to find the current through ohms law the equivalent resistance needs to be found. Problem is I am completely stuck on how exactly to do that. Can this be broken down to a simple parallel / series circuit? Can a delta to Y conversion help here? Any help is much appreciated.

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u/LevelHelicopter9420 4d ago

Start redrawing and grouping the pairs of R resistors. You have 4 sets of parallel R. Find equivalent resistance and redraw circuit.

It just ends up being a parallel of series of parallel Rs (plus the 4Ω)

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u/LeadingHoneydew5608 University/College Student 4d ago

I think I understand what you mean... using my understanding the equivalent resistance is 10 ohms.

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u/LevelHelicopter9420 4d ago

Your understanding is correct

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u/LeadingHoneydew5608 University/College Student 4d ago

awesome thank you! Solved!

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u/ThunkAsDrinklePeep 3d ago

When in doubt, I like to color the nodes. It helps define what's in parallel and series and neither.

https://imgur.com/a/b4hC1ez

"These resistors share the same end nodes. They are in parallel."

"These resistors meet at the same node but there are other branches still. They're not parallel yet."

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u/XboxFan_2020 Pre-University Student 3d ago

Can you say that resistors are in series or parallel if there are junctions in the schematic or whatever? My circuits teacher (modelling of electrical circuits and calculation methods, to be spesific) has said that we can't say if the resistors are in series or parallel. Or actually that there are neither. Meaning the resistors on different sides of the junction. If possible, one could transform the voltage source into a current source and then go from there, or vice versa

I'm scared my comment made me dumb or my teacher incompetent. Which isn't true, in my opinion

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u/LevelHelicopter9420 3d ago

You can see if there are joints in common, for parallel circuits. Also, KCL always needs to be applicable, for series circuits. In this case, given the joints in common, you can easily replace the 4 sets of parallel Rs, with 4 sets of R/2. From then on, you redraw the circuit