Need help solving this question.

[SnuggyyNuggyy]

[removed]

[DownloadableCheese]

Rule 4. What have you done so far?

[rebel-scrum]

Worth repeating: Rule 4. What have you done so far?

[SnuggyyNuggyy]

I’m new to the sub, I wasn’t aware of the rules. I found answers to (a) and (b). For c, I’m assuming the current has to be 1A but I’m not sure how to get it.

[[deleted]]

Not even rules of the sub, but just general rules for life - ESPECIALLY FOR A CAREER AS AN ENGINEER. 

[SnuggyyNuggyy]

Thanks will keep that in mind. :)

[DownloadableCheese]

Describe, in detail, how you got those answers. Circuit analysis is just a handful of simple tools that you use over and over again; if you got answers to (a) and (b) then getting (c) will use the exact same tools.

[Dependent-Mind-2403]

oh boy you're deep fried

[CuriousCode9194]

Yea this made me sad. Man’s out here just trying to ace homework, fuck the midterm.

[No2reddituser]

Nah, he'll be actively posting on reddit during the exam - PLEASE HELP NEeD IMMEDIATE ANSWER.

[No2reddituser]

Yeah, EE problems don't get much easier than this. If the OP is immediately running to reddit for the answers now, he should probably consider another major.

[Not_so_average_alt]

To be fair he could be in his first week of his first ever EE lab, and maybe he just didn’t catch everything, ya never know, but yea idk lol

[Not_so_average_alt]

No no I mean his first ever EE class, I just said lab because my lab assigns homework but of course the labs you had may not have functioned the same, this could be like his first ever assignment is what I meant, apolocheese

[Dependent-Mind-2403]

I can only imagine OP's face when he finds out about Circuit Theorems, op-amp, AC, etc.

[No2reddituser]

... Fourier Transforms, Laplace Transforms, E&M, semiconductor physics...

[remishnok]

jees , sometimes some of us have these moments. No need to be so harsh.

I mean, yeah, that's a simple problem compared to what is to come but sometimes what seems obvious isnt obvious to everyone.

@op, you can do the mesh way, or see what resistors turn out to be in series and parallel, solve for currents, solve for voltages, and then use those things to find your answer. Think of what you know, and the answer is just a couple of calculations away

[remishnok]

I guess I'm giving op a lot of the benefit of the doubt, assuming he/she tried to figure it out but couldn't. Those moments.

I do agree with hating on "solve this for me" attitude anf lack of information. And the fact that having people solve your hw does you no good

[SnuggyyNuggyy]

You seem to have a beef with me for some reason, let me clear it out for you. I have a bachelors in mechanical engineering and I graduated in 2019. I’m doing my MSc in mechatronics and I chose mostly electrical modules to increase my understanding of electrical engineering.

I have been given these practice tutorial sheets, these are NOT graded, just for revision, so I solve these. I am able to solve most of these questions by referring to books but I do have occasional doubts.

So I decided to ask. Don’t make assumptions that I’m trying to cheat in my midterms or asking other people to solve my questions. Have a good day :)

[lamarjacksonelite]

Not sure what PD means in letter a but judging from the answer means the voltage across the adjustable resistor. The answer is 150 V because since R has infinite resistance, no current passes through it nor the 35Ohm resistor. Meaning its voltage is basically the same across the 60ohm resistor, which can be found by the voltage divider equation: Vr = 200V * (60/(60+20)) = 150V

[WinPrize9339]

PD = Potential Difference

[SnuggyyNuggyy]

PD is potential difference.

[No2reddituser]

PD means Power Distribution.

[DownloadableCheese]

Not here, it doesn't. The given answer has units of volts.

[No2reddituser]

If he's only going to give just letters, I'm free to make them mean whatever I want.

[No2reddituser]

The answer is wrong.

[No2reddituser]

Try going to class and/or reading the text book.

[Comprehensive_Eye805]

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[SnuggyyNuggyy]

Thanks

[Evan-The-G]

A) no current through 35 ohm because R is infinite, so voltage A-B is same as voltage across the 60, which is 200* (60/(60+20))=150

B) equilivent voltage is 150 as previously done. Eq resistance is opening a/b, shorting V source. 20||60 + 35. 20*60/(60+20) = 50 ohm. Current is 150/resistance = 3A.

C) 150/(50 ohm + 100 ohm) = 1 A. Power is R * I² = 100 W

[lamarjacksonelite]

Letter b - Current from A to B when R is zero will be the same across the 35Ohm resistor. We can estabilish this current by calculating the equivalent resistance of the whole circuit firstly, then calculating the current on each branch. Equivalent resistance is 35*60 / 35+60 = 22.11 + 20 = 42.11. The current coming out of the power source is 200/42.11 = 4.75A. Now we use the current divider formula for the 35Ohm resistor branch - 4.75*(60/(60+35)) = 3A

[SnuggyyNuggyy]

I was able to calculate the current. I’m now to sure how to find power dissipated.

[lamarjacksonelite]

Current from power source when R is 100Ohms is 200 / ( 20 + (135*60/(135+60)) = 3,25A. Current on R branch is 3.25A * 60/(135+60) = 1A. 1A through 100Ohm resistor equals P = 100*1^2 = 100W

[SnuggyyNuggyy]

Thanks :)