Oscilloscope question #2 - Page 1
Forum section: electronics / beginners

author: Russ
author_rank: Regular Contributor
timestamp: January 31, 2018, 01:39:24 pm
content: A 6.2 Ohm Resistor and a 100 mH inductor are connected in series, across a 10 Vpp, 9.87 kHz sine wave power source. What is the impedance of the circuit?What is the phase angle, theta, of the circuit?A. 45 degreesB. 0 degreesC. 60 degreesD. 90 degreesThanks

author: rstofer
author_rank: Super Contributor
timestamp: January 31, 2018, 01:42:03 pm
content: 89.94 degreesAgain:http://keisan.casio.com/exec/system/1258032600

author: Russ
author_rank: Regular Contributor
timestamp: January 31, 2018, 02:05:40 pm
content: Quote from: rstofer on January 31, 2018, 01:42:03 pmThank you. I have to track down that Math app.Thanks

author: tggzzz
author_rank: Super Contributor
timestamp: January 31, 2018, 02:33:46 pm
content: Quote from: Russ on January 31, 2018, 02:05:40 pmNo you don't.You have to understand the theory of parallel and series impedances, plus complex arithmetic. Then you will be able to use any old calculator to solve the problem, including calculators you are allowed to have in exams.More importantly, you will get a gut feel for what's happening, and will then be in a good position to understand how circuits work, and when calculators and simulators are giving invalid answers.

author: rstofer
author_rank: Super Contributor
timestamp: January 31, 2018, 02:42:06 pm
content: The formulas are in terms of Henries and Ohms. Be careful about that! Omega comes from 2 * PI * freq in Hz.Plug the numbers into the equations and see what you get. I didn't do that because I am lazy. Also, it's not my homework.The best way to learn this stuff is to solve problems. You have a problem, you have the equations and, best of all, you have the solution. Grab up a calculator and work it out!

author: Russ
author_rank: Regular Contributor
timestamp: January 31, 2018, 02:44:02 pm
content: Quote from: tggzzz on January 31, 2018, 02:33:46 pm

author: Russ
author_rank: Regular Contributor
timestamp: January 31, 2018, 03:01:26 pm
content: Quote from: rstofer on January 31, 2018, 02:42:06 pmThanks. I keep working on it. But I have difficulty with mathematical equations. And I just cannot seem to retain the knowledge. Very frustrating 😬Thanks

author: rstofer
author_rank: Super Contributor
timestamp: January 31, 2018, 03:39:17 pm
content: I don't have to remember the formulas, I just need to remember where to find them. Google links to all of human knowledge - they're out there somewhere.I'm working with my grandson on Calculus I. Every time I come across an important concept, I write it on a 3x5 index card. I remember that I wrote it and I remember that it's on an index card, all I have to do is thumb through the deck.I had thought to use colored cards and separate concepts by color: Trig : yellow, Limits : pink, Derivatives : green, Antiderivatives : white. Something like that...The index card is a workable concept for EE as well.

author: Russ
author_rank: Regular Contributor
timestamp: January 31, 2018, 03:50:49 pm
content: Quote from: rstofer on January 31, 2018, 03:39:17 pmInteresting. I may go that route too. 👍Thanks

author: Mukrakiish
author_rank: Contributor
timestamp: January 31, 2018, 04:00:27 pm
content: Quote from: rstofer on January 31, 2018, 03:39:17 pm+1 to that. When I was taking Engineering, there was pages of formulaspercourse. Combined between them all there was a small book of just formulas to deal with (never mind the concepts), same idea as what rstofer is saying...basically keeping a tome of formula with key points as to the "what" and "why" for that particular formula helps the most.

author: rstofer
author_rank: Super Contributor
timestamp: January 31, 2018, 05:00:59 pm
content: There's another reason for the index cards: Creating crib sheets.At various times throughout the semester there are quizzes and exams. Other than the Final, these will cover specific sections of the material and crib sheets are allowed. So, we sort the index cards by topic and copy over the important formulas to an exam specific crib sheet.This may turn out to be more practical than having the same information in a notebook. We'll see...There's a reason that everybody remembers Ohm's Law and it's not just because it is simple. It's because it is used all the time. Nothing happens in electronics without Ohm's Law. The series RL formula isn't difficult, it's just hard to remember because it doesn't get the same attention as Ohm's Law. I suspect if a person used the formula a few hundred times before breakfast it would be as ingrained as Ohm's Law.Solve problems! That's the only way to learn the material.

author: Old Printer
author_rank: Frequent Contributor
timestamp: January 31, 2018, 05:32:23 pm
content: I never got the idea of taking notes in class, then rewriting them legibly that evening at home... so I didn't do it muchand my grades and knowledge showed the results. Now some 50 odd years later I am trying to teach myself the same stuff again, this time because I want to know it. Big difference. Now I understand that after writing it two or three times you are 80% of the way to remembering it without the notes, until age catches up with you and you can't seem to remember anything

author: tggzzz
author_rank: Super Contributor
timestamp: January 31, 2018, 06:40:30 pm
content: Quote from: Old Printer on January 31, 2018, 05:32:23 pmThe first part matches my experienceSo does the second part

author: Hextejas
author_rank: Frequent Contributor
timestamp: February 01, 2018, 12:43:24 pm
content: Quote from: rstofer on January 31, 2018, 03:39:17 pmI am a total beginner to this and was wondering what did you ask google so as to be able to find that formula ? I am going to try to solve it.This is a real challenge to me as the most math I had was in high school. I am not a dummy but have never been exposed to it.I do remember Ohms law however 😁I am also trying to learn how to use a scope and from this thread it seems like the slope of the trace is also important besides the amplitude and frequency. No need to explain why as I will eventually get to it. Just let me know that I need to pay attention to it.My area of interest is audio and building a better stereo.Thanks

author: rstofer
author_rank: Super Contributor
timestamp: February 01, 2018, 02:10:47 pm
content: 'series RL circuit calculator' without the quotesSecond reply was the one I picked because the first one was for a series R-L-C circuit.

author: Russ
author_rank: Regular Contributor
timestamp: February 01, 2018, 02:52:38 pm
content: I am just learning how to use the Scope, and with mathematical equations being a weakness of mine, I struggle with it.Thanks

author: rstofer
author_rank: Super Contributor
timestamp: February 01, 2018, 05:11:04 pm
content: You have a perfectly good example problem. You have the equations, you have the required data and you have a calculator. It is a good exercise to see if you can get the same answer.In effect, that's how we all learned this stuff. The book had the explanation and perhaps a couple of examples and there were problems at the end of the chapter. In many cases, the odd numbered problems had answers in the back of the book. Only the even numbered problems were assigned as homework but we could use the very similar odd numbered problems to convince ourselves we knew how to solve the even numbered problems.Watch some of Dave's tutorial videos. He has a couple (or more) on op amps:One on node and mesh analysis - Ohm's Law and Kirchhoff's LawsThere's a lot of material on the Internet.Here's a fairly extensive program on circuits:https://learn.digilentinc.com/classroom/realanalog/