Struggling to find current in DC circle.

Thread Starter

vadim_m

Joined Oct 23, 2016
2
Hi guys. I am struggling to find I2 and I3 in this circle. Can anyone help me please?
I've calculated:
RT=12.128kOmh
IT=0.989mA
I
1=0.527mA

Thank you

upload_2016-10-23_20-11-32.png
 

AlbertHall

Joined Jun 4, 2014
11,498
If you know It and I1 then you can calculate the current through the 10k resistor linking the I1 and I2 branches...and so on.

[EDIT] I haven't checked the values you have so far.
 

HunterDX77M

Joined Sep 28, 2011
104
You'll have the simplify the circuit by repeatedly applying Thevenin's theorem to get the voltage across each resistor. Then once you know the voltage, you can calculate the current. For instance, first you want to find the current through the 6.8k resistor. You would start by, would start by getting the equivalent circuit to the right of that resistor and use a voltage divider. Then keep going through the rest.
 

Thread Starter

vadim_m

Joined Oct 23, 2016
2
If you know It and I1 then you can calculate the current through the 10k resistor linking the I1 and I2 branches...and so on.

[EDIT] I haven't checked the values you have so far.
Still can't get it. Could you type an expression to find I2 please?
 

AlbertHall

Joined Jun 4, 2014
11,498
The current It flows through the 6.8k so you can calculate the voltage drop across it.
Now you can calculate the voltage across the I1 resistor and therefore you can get the current I1.
Then kirchoff gets you the current in the next 10k resistor in the chain and hence the voltage across it.
Now you can repeat the process for the next branch.
 

ci139

Joined Jul 11, 2016
1,696
Your R.tot is correct also I.tot and I1 - confirmed analytically in Excel also in LT spice
Keep it up - believing yourself
 

ci139

Joined Jul 11, 2016
1,696
Do NOT just give out answers to homework problems. If the instructor wanted the students to have answers to these problems they would have supplied them. Since they didn't, we need to honor their decision not to do so.
Draft_R-mtx_1.png incase you already didn't had the results to chk against
 

dl324

Joined Mar 30, 2015
13,082
you are not his personal advisor nor gonna track how he's progressing - as when he won't receive any help here when he's here - then what are we delaying here ? waiting him not managing it ? i'm confused
My point is that simply giving answers to students doesn't help them learn and can be considered cheating which would result in a failing grade if the teacher became aware of it.

It has been mentioned by others that teachers are aware of this forum.

Search this forum and you will see that AAC's policy, written or not, is that members will guide students to solutions; not give them answers.

When I was new to the forum, in my eagerness to answer an easy question, I once gave a student the answer. I was also admonished by a more senior member who knew the guidelines. I was just giving you the same advice. Do with it what you will.
 

dl324

Joined Mar 30, 2015
13,082
are the Distinguished Members the ones who complain most - such people - they don't do anything but complain - slow things down - make every ones life more complicated - for no other reason but to shine out and boss around
It is unlikely that someone who has contributed to the forums enough to become a Distinguished Member would have bad motives. It could happen, but would be highly unlikely.

Progress in Homework Help is mainly a function of the student asking the question. If you continue to frequent this forum, you'll find that many students ask questions and leave the thread when they see that they're expected to do most of the work.

The first sticky in this forum gives guidelines for students and members. This is a quote from @bertus, one of the administrators:
Lately we see people giving complete answers in the homework help section.This will hardly help the OP with understanding how to solve a question.
The people who help in the homework help section are supposed to give hints
The point of this section of the forum is to help students to learn; not help them cheat by giving them answers.
 

WBahn

Joined Mar 31, 2012
26,398
Still can't get it. Could you type an expression to find I2 please?
How did you get I1?

Describe the steps you used and then, if you haven't already figured out how to apply those same steps to find I2, we can help you see the connection.

The key step in this process is to consider that if you have 0.989 mA flowing into the node above the vertical 10 kΩ resistor and you have 0.527 mA flowing downward through that resistor, how much current has to be flowing to the left through the horizontal 10 kΩ resistor?
 

WBahn

Joined Mar 31, 2012
26,398
1-st no one come to seek help from the forum if they had plenty of time to struggle with it by themselves
Consider that they have seen the material presented in the text. They have seen the material presented in class. They have seen examples worked in the text. They have seen examples worked in class. Yet something still has not clicked. Why do you think that having someone give them the answers to yet one more problem is going to change that? They need to fight with the concepts themselves in order to find their misperceptions. That is best done by them working the problem as best they can and then having their work reviewed and observations made and hints given to help steer them onto the right path.

2-nd the best teacher is practice as well copy-writing the steps hopefully following and grasping why and what was done
And you deny them that practice by working the problem for them.

3-rd i only posted the results no formulas
So. How do you know that this is not an online assignment where all they have to do is plug the final answers into a webpage to get a grade?

Also, if the instructor chose not to provide answers to this particularly problem, might it not be because they had a reason for not doing so? For all you know the answers were provided for some problems and not for others.

4-th there's a lot of time passed since the OP was guided by other forum members - assuming he reached to point of solving his task already -- 12:58AM - 8:54PM = 4h4m
You call four hours a lot of time? For all you know the person started the thread shortly before going to bed, or to school, or to work, or to a concert in the park.

5-th if the OP has any common sense then he realizes to check for answers only if he has came out with something on his own - otherwise he wouldn't learn anything - and drop off the course in a longer run
There are LOTS of people that fish the forums looking for someone to oblige them and do their work for them. This particular TS may or may not fall in that category.

6-th considering the 2-nd - it's getting started - the next similar he is more likely to complete all by himself - the sooner that happens the less head ace for everybody
He needs to participate in the process by showing an honest attempt to work the problem. To date, zero work has been shown. That is his next step.

7-th you are not his personal advisor nor gonna track how he's progressing - as when he won't receive any help here when he's here - then what are we delaying here ? waiting him not managing it ? i'm confused
If you do not feel you can abide by the guidelines for assisting students in this forum (more specifically, the Homework Help forum of AAC), then don't participate in this forum. Feel free to start your own forum where you can solve students' problems for them to your heart's content. But stop doing it here.
 
Last edited:

WBahn

Joined Mar 31, 2012
26,398
reply to #12 #13 -- good you keep up your side -- otherwise we'd had imbalance here (i don't have to be responsible for new rules, muhahaa)

#15 -- i 'll likely have to take your advice (keeping away from HH) -- i don't take people as opportunists by default (? don't i ??? -- every physical system in nature likes to take the least energy state o_O*| . . . actually i have a an 50:50 different views to this - at college time my sisters class 2y ahead and my class were collaborative and sympatetic towards the other class members - but the one in between and the one following were the opposite -- so, should we throw the dice , blaah)
It's one thing to have an attitude on the small scale of giving people the benefit of the doubt, particularly in direct interactions with them, but consider the general, larger scale case. The overwhelming number of people flying on commercial flights are not trying to do anything they shouldn't. Yet all of them are subjected to security screening based on the realization that a tiny fraction of them are. The same with any number of activities and it is the same with forums such as this. Even if we presume that most people are NOT trying to cheat, the reality is that a significant number of them are. So we lay down expectations -- namely that people are expected to show their efforts -- that reflect that. But even more to the point, this coincidentally dovetails well with the most effective approach to learning material you are struggling with, namely to struggle with it in the presence of oversight by those that can provide nudges in the right direction.
 
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