(Just checking) What's the total resistance?

[Special One]

Homework Statement

Total R AB

Relevant Equations

Ohm's Law

 

[Gordianus]

It's O.K.

 

[DaveE]

Wow, what an annoying problem to be given.

 

[Special One]

Guys, I have never learned how to solve this kind of problem, Anyways I gave it a go and here's my answer. Can anyone correct me?

 

[DaveE]

Your good. No correction necessary.
Recognize that those crossed resistors could have been just drawn in parallel with the others. It's a stupid trick to make the problem look harder than it is. This is like your first problem, but with less stuff.
In my job with more complex circuits, I would often make the first step be "redraw the schematic to look simpler".
Anyway, it looks like you've got the basic concept. Just keep reducing the complexity of the network by combining resistors.

 

[Gordianus]

R35 is wrong. R3 and R5 aren't in parallel. I suggest moving the bottom of of R5 to the bottom of R6. Repeat with R3 and R2. Draw the new circuit.

 

[Special One]

R35 is wrong. R3 and R5 aren't in parallel. I suggest moving the bottom of of R5 to the bottom of R6. Repeat with R3 and R2. Draw the new circuit.

Do you mean like this?

 

[Gordianus]

No, don't move the top of R5, just move its bottom until it touches the bottom of R6

 

[Special One]

No, don't move the top of R5, just move its bottom until it touches the bottom of R6

I really didn't get it yet, do you mind drawing it for me please?

 

[Gordianus]

Can't draw with my phone. Follow my instructions. Keep the top of R5 at the junction of R4, R6 and R7. Noe move the bottom of R5 to the bottom of R6.

 

[phinds]

Recognize that those crossed resistors could have been just drawn in parallel with the others. It's a stupid trick to make the problem look harder than it is.

I completely disagree. It is exactly the kind of drawing that is given, and needs to be given, specifically to get beginners to learn how to recognize series and parallel elements.

 

[Special One]

Can't draw with my phone. Follow my instructions. Keep the top of R5 at the junction of R4, R6 and R7. Noe move the bottom of R5 to the bottom of R6.

you mean like this?

 

[Gordianus]

Now I like it.

 

[DaveE]

I completely disagree. It is exactly the kind of drawing that is given, and needs to be given, specifically to get beginners to learn how to recognize series and parallel elements.

OK, as a lesson in learning to read poorly drawn schematics, which they will surely encounter later. That seems like a worthwhile (but kind of annoying) vocational lesson, but not a great way to teach fundamental concepts.

I believe, after decades of working as an EE, that I can tell if you really understand electronics by how you draw your schematics; like reading tea leaves, I guess.

 

[Special One]

Now I like it.

Now, Are R4 & R6 in parallel?? the same thing with R2 & R3.

 

[phinds]

I believe, after decades of working as an EE, that I can tell if you really understand electronics by how you draw your schematics; like reading tea leaves, I guess.

Of course you can. But beginners DON'T understand it and they need to learn and this kind of thing teaches them. Perhaps you. like I, had a facility for this stuff right out of the gate but lots of EE students don't.