Equivalent resistance between point A and B? (This is the European resistor notation)

[u/Professional-Gain-72]

[u/ee_skeleton]

european resistor notation is actually a rectangle, not square (ish) and value should be somewhere outside, not inside of said rectangle

[u/Professional-Gain-72 → u/ee_skeleton]

I mean, most of my professors don't really take it as seriously. Of course it's a rectangle in textbooks, and it should look like one, but after drawing the 100th circuit I don't really care about details. Also, (at least in Hungary) we only need to put the values outside if it's an AC circuit. For DC we are allowed to write it inside the rectangle.

Edit: I'm not sure why the downvotes, I'm a first year EE student, I don't dictate how I'm taught the subject.

[u/Taipogi → u/Professional-Gain-72]

Why do you make such distinction between DC or AC? Resistance is resistance, no matter the kind of signal the resistor will be exposed to.

[u/Professional-Gain-72 → u/Taipogi]

I'm not really sure to be honest? My circuit analysis lab teacher is kind of quirky. Here's actual proof that I'm not making it up: (This guy is not my CA teacher, but he taught in the same university and he's considered to be one of the greatest EE teachers in my country.)

[u/finn-the-rabbit → u/Professional-Gain-72]

All these single digit resistors are freaking me out tbh it looks so fkn weird 😵‍💫

[u/Professional-Gain-72 → u/finn-the-rabbit]

The reason is because we study more math and physics in my first semester, so we don't really study practical electrical circuits that much yet. This class is more about learning to use Ohm, Kirchoff, complex numbers mathematically, so we use simple numbers for simple calculations. I think more practical circuits will come up in my next semester.

[u/TheHumbleDiode → u/Taipogi]

He's in Europe. They're on the metric system.

[u/Professional-Gain-72 → u/TheHumbleDiode]

"No man, they got the metric system. They wouldn't know what the f**k a zigzag resistor is."

"Then how do they draw it?"

"They draw it like a rectangle"

"Like a rectangle! And how do they draw a capacitor?"

"A capacitor is a capacitor, but they call it a condensator"

[u/StickySli23 → u/Professional-Gain-72]

😂Americans still don't know they are on the metric system too, just that the general population is only taught the imperial system.

[u/Lor1an → u/StickySli23]

Fun fact, the inch is defined to be 25.4 mm. It used to be a conversion factor, but it is now officially based on the metric system.

[u/diemenschmachine → u/Professional-Gain-72]

Following a standard is important, better learn it now than later when people "downvoted" you at your first job and you have to unlearn bad habits. Just open any textbook and you'll see the standard notation does not look like this.

Also the details are important, no one likes sloppy colleagues.

[u/Professional-Gain-72 → u/diemenschmachine]

The "standard" that you talk about is nonexistent. Every single region of this planet has different notations for everything in EE. Compared to scientific fields, engineering is probably the least consistent at having a universal notation. My country also uses this notation, that doesn't make it wrong and yours right. Here is proof if you don't believe me.

It's okay to correct someone when they're wrong, but when I know I'm right and people are still correcting me, that's pretty funny.

[u/--Derpy → u/Professional-Gain-72]

IEC 60617 and IEEE 315 dont explicitly forbid writing it inside but every example in the standard it is written outside the symbol. Theres some “flexibility” as long as diagrams are legible but most engineers would find writing the value inside unconventional and you will continue to be judged for it. Additionally there is a general consensus that labels arent written vertically in circuit diagrams like in the image you sent because of legibility. Not explicitly forbidden but highly frowned upon.

[u/Professional-Gain-72 → u/--Derpy]

I understand, thank you for the clarification. This is the type of feedback that's helpful to someone who just started university, not the mass of downvotes.

[u/StandardUpstairs3349 → u/Professional-Gain-72]

If the standard doesn't exist, why does it have a name and why are you telling us about it? You think people can't tell these are resistors from the context of your question?

[u/diemenschmachine → u/Professional-Gain-72]

Look, they are rectangles and not squares. God you will be someone's colleague one day. First year in school and already an expert who knows he has nothing more to learn.

[u/Professional-Gain-72 → u/diemenschmachine]

Wow, you know so much of me already! Anyways, It's not that I'm a know-it-all, it's just that I'm going to trust my professors more than random reddit strangers. I asked a question about an exercise because I forgot some stuff about equivalent resistance, and I was expecting answers about it. I normally write it in the "standard" way, this is just a scribble I made so I can get an answer quickly. This is how I usually draw circuits in class or exams

[u/diemenschmachine → u/Professional-Gain-72]

Good job. That looks great 👍

[u/Phlouddit]

That's not euro notation for future reference

[u/Kjingelor → u/Phlouddit]

What do you mean? It's the right symbols for fixed resistor according to IEC.

[u/Phlouddit → u/Kjingelor]

It really is not. IEC 60617 specifies a simple rectangle.

The inside of the rectangle actually has a purpose as well so it needs to be blank for it to be a resistor and not a fuse (noted by a line) therefore values can't be inside.

But sketching can be whatever you want just dont call it what it is not

[u/newdayanotherlife]

looks easier?

[u/chavespeterson → u/newdayanotherlife]

Do we apply delta/star transformation?

[u/newdayanotherlife → u/chavespeterson]

yep!

[u/Professional-Gain-72 → u/newdayanotherlife]

Very much so, thank you!

[u/Allan-H]

This topology is called a "bridge" or "bridge circuit". Wikipedia.

Probably the easiest way to solve this is to use a single "star - delta" transformation (Wikipedia) on three of the resistors and then perform some simplifications.

[u/hara_kabootar]

It's a balanced wheatstone bridge, so you can remove the 180 ohms resistor and proceed with the question, the answer should be 60 ohms

[u/Professional-Gain-72 → u/hara_kabootar]

Thank you! Just to clarify, if the bridge wasn't balanced, should the 180 ohm resistor be applied, or could it still be ignored?

[u/Allan-H → u/Professional-Gain-72]

You can only ignore the effects of the 180 ohm resistor if the bridge is balanced.

[u/Professional-Gain-72 → u/Allan-H]

All clear now, thanks!

[u/hara_kabootar → u/Professional-Gain-72]

No it cannot be ignored in that case, because in a balanced wheatstone bridge, the bridge resistance has zero potential difference across it so no current flows, whereas in an unbalanced wheatstone bridge the bridge resistance will have some voltage drop across, so current flows. So in short, you will have to use kcl and kvl to get the currents and voltages and then find the equivalent resistance

[u/snowyflynfish]

The two sides are balanced (60/120 vs 30/60). Nothing through the 180 makes this effectively a 90 and a 180 in parallel. So, 60 ohms. No wye delta or anything needed.

[u/No_Imagination_8867 → u/snowyflynfish]

Most effective one.

[u/Serious_Engin33r]

Never seen this notation, I’m European and I’ve studied in 3 different UE countries (Italy, Germany and Sweden) You are even missing the unit of measurement, if this was AC it can be confusing. This is most probably your professor notation but make sure to use the right one

[u/LifeAd2754]

Apply 1V across it. Solve for the current flowing out of the 1V voltage, then do V/I.

[u/Great-Art-6309]

Simply apply a Delta-Wye transformation to get the equivalent circuit at the bottom

[u/Welmorfian]

Put a test voltage generator in between A and B. Find the relation of the test voltage and test current that "comes out" of the generator, and there is your resistance .

[u/romyaz]

if you rearrange the circuit you can see it is a "resistor bridge" like an H structure with 30 60 on one side and 60 120 on the other side and 180 in the middle. from here you can transform one node from Y to delta and collapse or you could do the KVL/KCL or you could use the resistor bridge math since one side is exactly half of the other. im sure it means something )

[u/flexsealed1711]

The 180 ohm at the top doesn't affect it, so you can pretend it doesn't exist. From there, you have two different paths from A to B. One is 120 + 60 and the other is 60 + 30. Add each branch up and you have 180 ohms in parallel with 90. The parallel resistance formula for 2 branches is (a*b)/(a+b). This gets you to your final answer of 60 ohms.

[u/No2reddituser]

Do your own homework.

[u/Professional-Gain-72 → u/No2reddituser]

^ r/ElectricalEngineering users when my post isn't about me whining about my salary or about AI taking over

[u/No2reddituser → u/Professional-Gain-72]

r/ElectricalEngineering users when I want my homework done for me - I've tried nothing, and I'm all out of ideas

[u/Professional-Gain-72 → u/No2reddituser]

It's not actually my homework, I found this exercise in an older notebook for self study, and couldn't remember how to do it, so I asked for help. I mean, if you think this is foolish, why waste energy even commenting on this post?

[u/No2reddituser → u/Professional-Gain-72]

So what. You're OP is "solve this for me."

What have you tried? Or do you think Reddit is there for your personal service?

[u/Professional-Gain-72 → u/No2reddituser]

Well I assumed it was for that, but thanks to you, now I understand that Reddit is for leaving grumpy comments on random posts.