What's wrong with this circuit? - Page 1
Forum section: electronics / beginners

author: Nexo
author_rank: Regular Contributor
timestamp: September 13, 2016, 04:48:36 am
content: Hello everyone!Can anyone tell me why is my circuit shorted?

author: IanB
author_rank: Super Contributor
timestamp: September 13, 2016, 04:52:59 am
content: Quote from: Nexo on September 13, 2016, 04:48:36 amBecause there is an unbroken line from one side of the voltage source to the other.

author: Nexo
author_rank: Regular Contributor
timestamp: September 13, 2016, 05:11:46 am
content: Wasn't that clear? Haven't I stated that th E circuit was shorted? I did state that, thus, your comment has no meaning. Please, I would be so glad if you posted somewhere else but here, I can't handle people like you. With all due respect, of course.

author: Brumby
author_rank: Unknown
timestamp: September 13, 2016, 05:14:21 am
content: Youhavebeen told.But if words are not enough:.....Red is the Voltage SourceBlue is the Short CircuitSpecifically, you have a wire going from one side of the voltage source to the other - with some components hanging off it which do absolutely nothing.

author: Nexo
author_rank: Regular Contributor
timestamp: September 13, 2016, 05:14:43 am
content: Thanks for your response. You mean that in the left path, as there are no resistors the current will prefer that path than the one with resistor on it? I thought about that, I just wanted to make sure my reasoning is correct and as this forum is called beginner's forum, I'm not afraid to ask stupid questions, even tho there are a few guys out there that would rather make fun than help.Again thanks for your reply!

author: MK14
author_rank: Super Contributor
timestamp: September 13, 2016, 05:20:02 am
content: Quote from: Nexo on September 13, 2016, 05:14:43 amWhere are the posts that are making fun ?I can't see any ?I can't find anything wrong with the other posts in this thread.

author: Brumby
author_rank: Unknown
timestamp: September 13, 2016, 05:25:00 am
content: I have often found the only stupid questions are the ones that people DON'T ask.Yes, your question was basic - extremely basic - and some people might not see it as a valid question. I admit I paused a minute before replying.Your reasoning is correct .... and in the not-too-distant future, you might look back on this and realise how very basic and obvious the question was.Don't worry too much about any of the responses here, just continue with your interest and please come back with more questions. Pretty soon you will be coming here with more interesting ones - and there are a lot of people that can and are more than happy to offer help.

author: Nexo
author_rank: Regular Contributor
timestamp: September 13, 2016, 05:26:12 am
content: I haven't said that there is someone that mocked somebody here, I just stated a fact. Now what I just can't handle is the comment that says that "I'm trolling because I ask this (stupid) question". I don't know if I have to remind I'm every single post that this is a BEGGINERS FORUM. Anyway, let's cut the drama.Again, thanks for your help. Specially to the one who posted the image.Have a good day.

author: Nexo
author_rank: Regular Contributor
timestamp: September 13, 2016, 05:31:52 am
content: Quote from: Brumby on September 13, 2016, 05:25:00 amCouldn't agree more and now I see how basic this question is, thanks again for you kind reply. Just for the record, I have been solving some pretty hard math's question and is midnight here so I'm pretty tired and found this circuit and my tiredness didn't let me use my brain... Everyone has there "5 seconds of stupidity everyday" I guess I just used mineAgain, thanks! Have a great day, buddy.

author: MK14
author_rank: Super Contributor
timestamp: September 13, 2016, 05:34:38 am
content: Quote from: Nexo on September 13, 2016, 05:26:12 amI now understand why we had differing views on what one of the posters said.I doubt they meant anything bad (by saying troll). They were just defending their answer, against the possibility, that instead of being a real genuine beginner, you might have been someone messing about.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: September 13, 2016, 07:48:25 am
content: Well.... so far the answers have been answering "HOW is the circuit shorted." Yes, there is a wire directly connecting the positive and negative ends of the voltage source. That's pretty obvious from the schematic. Painfully obvious in fact.But we still don't know "WHY" the circuit is shorted. That is, why did the OP design the circuit that way, with the obvious short in it? What was the OP trying to achieve with this circuit? It seems clear to me that a non-functional circuit incorporating a direct short across the power supply probably wasn't the intended result.

author: MK14
author_rank: Super Contributor
timestamp: September 13, 2016, 10:49:36 am
content: Quote from: alsetalokin4017 on September 13, 2016, 07:48:25 amI wondered about exactly the same thing, and would have preferred to know more about WHAT exactly they were trying to do. Then we could probably guess the rest of the details, and help them best.I'm guessing, but either the 20 volt, voltage source was suppose to be directly across the paralleled resistors, to make a much lower valued resistor.Or they were trying to experiment, with different resistor network connection types, and accidentally (without realizing), ended up shorting out the whole thing across the power supply/source.

author: Augustus
author_rank: Regular Contributor
timestamp: September 13, 2016, 11:20:24 am
content: Was probably part of a school exercise or class test

author: Watth
author_rank: Frequent Contributor
timestamp: September 13, 2016, 02:05:18 pm
content: Quote from: Augustus on September 13, 2016, 11:20:24 am^ This.When someone asks a quite basic question and gets angry at the answer not being straightforward enough, it really sounds like the OP has to solve an assignment and is getting too close to the dead line.Likethe one who wanted to add a beep sound to every keyboard entry of an Arduino based calculator- really, if they were a hobbyist they would have appreciated the pointers that would lead themto find a solution by themself - but got annoyed at not being given a plain code line - and if it was not a hobbyist, whoneedsan Arduino calculator?This is also accentuated by the fact that the question are poorly constructed and no context, i.e. the OP doesn't really understand the question they're asking.There's nothing wrong to ask questions about an assignment, but it seems that EEVfolks know that giving directly the answer won't help the OP in long term and would rather direct them to find the answer by themself.

author: void_error
author_rank: Frequent Contributor
timestamp: September 13, 2016, 02:10:23 pm
content: Quote from: blueskull on September 13, 2016, 05:18:32 amI'm inclined to think it might destroy the universe, since an ideal voltage source will output an infinite current into a zero ohm load. Don't take this too seriously.My apologies for being slightly off topic, as the OP's question was already answered.Quote from: Watth on September 13, 2016, 02:05:18 pmNot blaming anyone here, but it would have been easier if the OP stated whether this was an assignment or not, or formulate the question in a different way.We all had our brain farts followed by facepalm moments...

author: edy
author_rank: Super Contributor
timestamp: September 13, 2016, 09:19:37 pm
content: This is the beginners forum, so keep in mind some people are *really* beginners. I've posted another problem for the OP, maybe it will help them understand better. Almost the same circuit... but I've moved one wire (the bottom one) from one side of the resistor to the other.This new circuit "fixes" the short-circuit. Now you can do some calculations to test your knowledge. Some are obvious, which may seem like a trick question.1. What is the current through each resistor?2. What is the voltage drop through each resistor? (yes this is an obvious one)3. Can you replace the 3 resistors with 1 resistor that does the same job?4. Why would you use 3 resistors instead of 1?5. What happens if 1 of the resistors "blows". What will the new current/voltages be on the remaining 2?Anyways, just a few basics...

author: Nexo
author_rank: Regular Contributor
timestamp: September 14, 2016, 12:11:02 am
content: Quote from: MK14 on September 13, 2016, 05:34:38 amYep, it was only that part that made me feel a bit uncomfortable.Quote from: alsetalokin4017 on September 13, 2016, 07:48:25 amAnd this is obviously a "Beginners forum".Painfully obvious in fact.I didn't design it and I didn't make that point clear. My bad.Quote from: Augustus on September 13, 2016, 11:20:24 amYes it was, thanks for pointing it out.Quote from: Watth on September 13, 2016, 02:05:18 pmDid I get angry? I don't think so and MK14 might agree with me on it. (Read previous replies, please).Quote from: void_error on September 13, 2016, 02:10:23 pmI just wonder HOW would that be helpful or make something "easier"? Even if it was an assignment or an exercise on a textbook the answer would've been the same, right? There is a path with no resistance and the current would flow through that path. I just can't see how could the context affect the result. But that's just me.Quote from: edy on September 13, 2016, 09:19:37 pmI really appreciate the time you took to write this reply, I'll start solving that exercise and it might be really straightforward for almost everyone in this forum but some of those guys forget that nobody is born knowing a subject and start using some quite questionable adjectives but whatever, I'll keep asking stupid questions because I'm pretty sure that if one of those guys would like to know something about and airplane engine (my strong subject) I would never use those adjectives... Maybe some people SHOULDN'T be on this beginner's forum if they are not willing to come across some pretty "painfully obvious and stupid -that might even look that the OP is teasing them- questions".Anyway, I really want to thank those who helped me, you guys rock. Wish you all the best!

author: Brumby
author_rank: Unknown
timestamp: September 14, 2016, 01:27:27 am
content: This:Quote from: edy on September 13, 2016, 09:19:37 pm.... .... ....Nexo, please do not get put off with anything posted here that might seem critical. It will settle down soon and you will find the environment much more comfortable.

author: edy
author_rank: Super Contributor
timestamp: September 14, 2016, 01:50:54 am
content: Quote from: Nexo on September 14, 2016, 12:11:02 amAfter you've worked on the problem a bit, give us your answers and I'm sure we will be glad to help you through them if you are stuck. Everyone has to begin somewhere. Hint: V=IR (Ohm's law) is where it all starts. There are also some rules about how resistors work in series and in parallel. There are a bunch of lessons here:http://www.physicsclassroom.com/class/circuits/Lesson-4/Parallel-Circuits.Like Brumby said, don't get caught up in the politics, but do elaborate more one what you are doing, what level/grade/education you are at (so we know the kind of math/physics to throw at you) and show that you've put some effort first to understand and why you are getting stuck on the concepts or calculations. There are a lot of people on here who are great natural teachers who are happy to share their knowledge, but will feel good knowing it is being received and understood... no better reward than that.And we'll be here to nudge you along in your electronics knowledge growth when you are confused (like I was when it came to capacitors for the longest time... but that's another story).Some tools to help you:Ohm's Law calculator:http://www.ohmslawcalculator.com/ohms-law-calculatorParallel resistor calculator:http://www.1728.org/resistrs.htmOnce you see what's going on, it should *intuitively* make sense. It takes time to build that intuition though. The math will also make sense and the way that resistors work, and why resistance changes based on the configuration (parallel vs. series) and how the current works and changes in these circuits all will eventually become clear.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: September 14, 2016, 06:19:22 am
content: OP has stated this is a school exercise. I can see two possibilities.1. The instructor threw this in as a bit of trick question to test the true level of understanding of the students. The answer seems too be to simple to be true, and only a fairly confident student will consistently answer a question like this correctly.2. The instructor doesn't really understand the subject matter and put this question in without understanding what they did. A mistake, uncaught due to incompetance.I would have trouble placing odds on which possibility is more likely. I have seen both things happen.

author: MK14
author_rank: Super Contributor
timestamp: September 14, 2016, 12:43:05 pm
content: Quote from: Nexo on September 14, 2016, 12:11:02 amIt is very useful to know the context under which the question, is being asked. Because the extra information that gives, can help others make more accurate guesses, as to what has really gone wrong.E.g. If I say I bought a component from China, and it seems to be faulty, they can say that components from China are often fake/faulty and/or of poor quality, so get a decent replacement component to fix the problem.If I say I bought the component from Digi-key, and used a super cheap unbranded multimeter to check the component. They might say the multimeter is probably junk, try using a proper multimeter to test the component, as Digi-key components are usually good quality.If I say a teacher gave me a schematic and I don't understand it. They can expect that there might be puzzling/trick concepts potentially built into the circuit, to catch out people learning electronics. Such as short circuits, put in to catch out unwary students.So I would say the context does make a difference.If we had known it was from an educational problem set as a work assignment, we would have been more inclined to hint at the solution, to help you sort it out yourself. Which is probably the best long term solution, rather than just giving you the answer, which is not so good, if you are suppose to be learning about it yourself.

author: TheBay
author_rank: Unknown
timestamp: September 14, 2016, 01:20:56 pm
content: Wouldn't have been shorted if it was RF though, but there is a power source there so can't be that

author: edy
author_rank: Super Contributor
timestamp: September 14, 2016, 06:12:05 pm
content: By the way, I find that even when I have to answer seemingly "simple" questions, it makes me think about them in a new way that makes me understand the problem better. For example, even with this parallel resistor problem and calculation, I have come to appreciate what is going on better and have a deeper understanding. That is the beauty of teaching, it makes the teacher discover things over and over again. As you teach classes year after year (as I have done), I get different questions and this makes me get the ideas at a deeper level which can help me teach better as well.In this example, it may not seem intuitive that overall resistance through the path drops as you hook up more resistors in parallel. Yes you can blindly follow "the rules" and use the formulas, but WHY does it drop more and more, and what happens if you increase the resistors to infinite numbers in parallel? It helps when you understand current and how it divides up between components, and also what the voltage means and how it changes. So even a simple problem that can be easily solved with a few math rules to get the right answer, gives you a lot more understanding when you actually think harder about it.