Complex Resistor Circuit seatwork - Need Help please

Thread Starter

scarletchrome

Joined Sep 13, 2015
5
My professor gave as a seatwork(picture attached). Then I tried to identify which is series or which is parallel, then i realize that it cant be reduce into a single resistor component which makes it a complex circuit(based on the video here at AAC). Then if I cant reduce it how will then will I be able to solve this? I need help and clarification about this. My professor is bot much of that help and he is quite annoying.
 

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Jony130

Joined Feb 17, 2009
5,176
Are you sure it cannot be done ?
What if you add (2Ω + 4.5Ω) and this is parallel to 2.7Ω and all of this is series with 3.3Ω and so on.
 

Thread Starter

scarletchrome

Joined Sep 13, 2015
5
Im having complications because of the junctions. Is it alright to combine (2Ω + 4.5Ω) with (2.7Ω which is in junction with other components from both sides)?
 

WBahn

Joined Mar 31, 2012
25,918
My professor gave as a seatwork(picture attached). Then I tried to identify which is series or which is parallel, then i realize that it cant be reduce into a single resistor component which makes it a complex circuit(based on the video here at AAC). Then if I cant reduce it how will then will I be able to solve this? I need help and clarification about this. My professor is bot much of that help and he is quite annoying.
What video here at AAC? It would help if you provided a link to what you are referring to.

What you do you mean by "makes it a complex circuit"? The term "complex" has a pretty specific generic meaning in electronics, namely a circuit containing both resistive and reactive elements such that it is best modeled using complex numbers. But I don't think you are at the point yet.

Take a close look at the circuit? Can you not identity even a single pair of resistors that are in series (or in parallel) such that you could combine them. If you do, then do so. Then look at the circuit again and see if you can identify another pair. Wash rinse, repeat.
 

WBahn

Joined Mar 31, 2012
25,918
Im having complications because of the junctions. Is it alright to combine (2Ω + 4.5Ω) with (2.7Ω which is in junction with other components from both sides)?
Work from the definitions.

Two resistors are in series -- and, hence, can be combined into a single resistor -- if whatever current flows in one MUST flow in the other.

Two resistors are in parallel -- and, hence, can be combined into a single resistor -- if whatever voltage appears across one MUST appear across the other.
 

WBahn

Joined Mar 31, 2012
25,918
A good place to start on something like this is to just get a pair of bounding values. Since ALL of the current that leaves the battery MUST go through the top 3 Ω resistor, you KNOW that the total resistance MUST be at least 3 Ω. Now identify the single path from one terminal of the battery to the other that goes through the smallest total resistance. That turns out to be the path through the 3 Ω resistor and then through the diagonal 2.7 Ω resistor back to the battery. That sets an upper limit on the total resistance of 5.7 Ω. So now you work the problem and if you get an answer that is not between those two limits, you KNOW the answer is wrong. Also, if you just put down this much as your answer, you might get considerable partial credit (and, in the real world, knowing the total resistance to within those limits might well be good enough).
 

WBahn

Joined Mar 31, 2012
25,918
Thank you Sirs.
http://www.allaboutcircuits.com/video-lectures/complex-circuits/ - here is the video where I based my conclusion.
I've never heard a circuit containing resistors that are in neither series nor parallel a "complex circuit", but I can see why that term might be used. I think most people refrain from using it because they know that, eventually, the term "complex circuit" is going to naturally refer to something quite different.

But in this case, the circuit is NOT complex, even by this video's definition.
 
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