Hi everyone I'm looking how to find time of a sine wave

Merry Christmas

Scottywatt

Member
Location
Mass
Occupation
Electrician/ Construction
I wish I knew because they are not giving information All it is is a box with a wave and on the bottom outside the box Is says something like W Div/.011
That's it


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Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
I think you are missing the point there not giving any information I don't need at this point to learn all about sine waves they don't teach journeyman these things and I would like to pass the second half of the test I don't have the luxury of learning every aspect at this point it takes too much time no one seems to have the answer


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No matter what answer we give you it isn’t going to help you pass this test.
If you can’t describe the test question accurately we can’t give you the correct answer.
if we give you the answer will that exact question be on the test?

If I sent you this would this make sense to you?
Quite honestly this reads like rambling…

They ask this on the exam in mass they only had a square box with a full wave with nothing Else in box; but on the bottom of the box which I couldn't read it was too small they had what looked like cm/.011 or something to that defect they ask at the half way point what was the number and then again ask another question asking other questions answers that jumped out at me which they had 4 was 10 and 5 So I picked 5 Didn't do anything like that in training so I don't know Thanks

Its like we are required to be a clairvoyant to interpret what you are asking here.

FWIW, I agree that it’s a silly question for nothing more than a journeymans test.
 

Scottywatt

Member
Location
Mass
Occupation
Electrician/ Construction
That's ok May be too complicated for you maybe there is calculus involved who knows the question was put there because it can't be answered and there screwing with everyone as everyone does until they come down with cancer or something oh well


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Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
That's ok May be too complicated for you maybe there is calculus involved who knows the question was put there because it can't be answered and there screwing with everyone as everyone does until they come down with cancer or something oh well


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Yeah, that’s it…
;)
 

Carultch

Senior Member
Location
Massachusetts
That's ok May be too complicated for you maybe there is calculus involved who knows the question was put there because it can't be answered and there screwing with everyone as everyone does until they come down with cancer or something oh well


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It probably has to do with knowing the general patterns of sine waves, and knowing how to measure attributes of sine waves, such as amplitude and period, given a graph of the wave. You can determine amplitude and period, even if you are only given part of the graph. There is symmetry to the sine wave, so even if you only can see a quarter of the wave, you can infer what the rest of the wave looks like, given that it is a sine wave instead of some other irregular waveform. Obviously you need to be given enough information to establish a scale for both axes of the graph.

"W Div/.011" sounds like they are telling you that Watts = divisions divided by 0.011, meaning that the scale on the Y-axis represents power in Watts, and every division drawn is (1/0.011) Watts.

There are Calculus problems with sine waves that are applicable to electricity, but this doesn't sound like one of them. One example is the theory behind the term "RMS", which is the basis for nominal voltages and currents of AC waveforms. The reason why what we call "120V AC" is really a waveform between the extreme points of +170V to -170V . Even if Calculus were involved, the Calculus of sine waves is very elegant, compared to all possible problems you could get in Calculus. I wouldn't expect a Calculus problem to occur on a Journeyman's exam. Maybe on the FE or PE exam instead.
 
Last edited:

Scottywatt

Member
Location
Mass
Occupation
Electrician/ Construction
Could be anything but because I don't know anything about it and was never schooled in the subject for exam prep I wouldn't know and I was surprised to see that kind of question and many other like it on that level of exam. Bottom line there were about 9 questions on that type of level a lot of it that wouldn't pertain to any journeyman doing work. So I can only draw the conclusion that they do not want people to pass, of course this would explain why no one is there every time I go. Maybe ???


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Scottywatt

Member
Location
Mass
Occupation
Electrician/ Construction
Basic questions like what that's not something that is taught even in mike holts courses I don't know how you can say it's basic typical sounds like you are the typical electrician who is a know it all that's sends there helpers to jobs and charges electrician rates


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tom baker

First Chief Moderator
Staff member
On top of that I don't know why they would ask or e spect a journeyman electrician to know this on the practice portion of the exam I already passed the code portion


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When you are asked to troubleshoot a generator, knowing how to measure frequency is essential. You are not tested on what you do in the job, you are tested on your scope of work
 

gar

Senior Member
211016-2107 EDT

Scottywatt:

You seem to have an attitude problem, and it may be valid in this case. I have no way of really judging. In my opinion you should want to learn new things. Do you really just want to pull and terminate wires the remainder of your life?

You are confronted with a question you do not understand. Is there some information in other questions that might provide additional information that is not presented in this particular question? I believe you have provided us with some information from the problem. What I don't see is the exact question. All I am able to conclude from your posts is there is a rectangle and in the rectangle is a sine wave with a very poor verbal description relating in some fashion to the sine wave. I do believe that you wrote the word "sine", and I believe the website or your computer changed the spelling. I have that problem all the time on this forum. I just had "life" changed to "like" ( I caught it ).

The scale labeling you mentioned, whatever it is, seems very strange.

.
 

Besoeker3

Senior Member
Location
UK
Occupation
Electrical Engineer
Basic questions like what that's not something that is taught even in mike holts courses I don't know how you can say it's basic typical sounds like you are the typical electrician who is a know it all that's sends there helpers to jobs and charges electrician rates


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But you'd be wrong. And I don't think I can help you any further.
 

Scottywatt

Member
Location
Mass
Occupation
Electrician/ Construction
Yes it's always good to learn new information. If I ask you to chase a ball and made the ball invisible you would never be able to get the ball unless you learned something that would allow you to see it. The point is they don't want people to pass the exam if they are asking these type of questions. Now the question is why and unfortunately it always comes down to greed and politics. If there is a pattern of abuse and there is a money trail then eventually people find themselves in federal court and then prison. This is unfortunate but this is the world we live in.


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Fred B

Senior Member
Location
Upstate, NY
Occupation
Electrician
Another view is sometimes on these practice exams they will have typos, then there is no answer, this is practice exam? Then you should have an answer key. Sometimes you can desifer intent of question from the given correct answer even if wording bad. (But not always if all parts are incorrect from typo)

AFA not needing to understand sine wave form for a journeyman, that is bad thinking. Journeyman is not the end of the journey in the electrical field, after this is a master electrical, or can move toward engineering. If you want to be more than a guy that just throws parts at a problem and pulling wire through an attic, at least a basic understanding of the concepts is useful, even if you don't use a scope or get to the advanced level some of these guys who have commented have. (I'll admit not experienced with some of their advanced levels but great hearing from them and still learning from them, thanks guys for your input.)

You'll see many threads on this sight related to troubleshooting that really have at the heart of it the basics of a sine wave form and deviation that indicates a possible source of the problem. (Like why is the dimmer causing flicker?, or why can't or will a 50hz equipment work on typical American electrical system? Or, How does Generator load shedding work?) Most of us do not use an occiloscope as part of our diagnostic repriteuar but it is still a relevant portion of what is really happening electrically, behind the scenes.

One simple inference from your test question wording could be that it is asking the actual voltage at the mid point of the sine wave? What would then be you answer. Or it could be asking the time interval from midline to midline on a 60hz system? What then is the answer. Too many possibilities for what the question really is. Questions related to basic understanding of a sine wave I think would be relevant and within the scope of a journeyman test.

An attitude will not help your cause and will actually get in the way on the job.
Like everyone already said your question as stated gives inadequate information regarding what is expected from the sample test, perhaps getting the actual wording rather than your interpretation of the wording might help, don't know.
 

Scottywatt

Member
Location
Mass
Occupation
Electrician/ Construction
It's not a practice exam and was not taught to me or anyone I know for a journeyman test .this was on a state exam NOT CODE I passed the code and calculations and all of that with flying colors, which was a challenge because I'm autistic with ADHD. As far as my writing I can't stand typing on this I phone and it seems to do what it wants to do all the time. Of course the I phone has a 1000 page manual from what I understand but I wouldn't want to know every aspect of that either. What I enjoy doing is working in old houses fishing wires and doing renovation work. I don't see my track taking me to commercial or industrial I'm just not interested in it. The question I was referring to was one of many probably 9 questions in total like capacitors in series which again was not taught in classes. So in closing electrical is such a broad field I would find myself chasing for a bunch of answers to questions that were never presented to learn and it would only be a waste of time. I don't think there is any Electricain out there that knows everything about every aspect of electrical and half of the older ones still believe a ground rod is there to protect people from being shocked.


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Scottywatt

Member
Location
Mass
Occupation
Electrician/ Construction
What would really impress me if someone actually could teach it to me. Because when you try to look it up on you tube or Google people tend to try to impress others by what they know not realizing they are not helping anyone but maybe there own ego


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Scottywatt

Member
Location
Mass
Occupation
Electrician/ Construction
Also I do appreciate all the feedback it's just over my head I have not been exposed to it
All I know is there is a wave because it's alternating current and it fluctuates by the load such as voltage would lead the current in a inductive type load. The switching back and forth of computer monitors, servers non type linear loads cause a distorted wave form due to harmonics reflective currents slamming back and forth due to the switching from what I understand a 3 phase load the phases are 120 degrees from each other. From what I understand a full wave is 360 you have peaks high and low. I do have some knowledge about it. Yes it does go back to basic electrical as far as where it is generated but may not be that useful to me doing residential work. Yes it would be good to know and I appreciate all the input from everyone. What would impress me would be if someone could actually teach me about it instead of beating me up saying you should know this or that. It's funny because when I ask people I know taking the test they had no clue what I was talking about and didn't know half of what I just stated. It's a rough world we live in when people pretend to help but in reality there helping there own egos


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Carultch

Senior Member
Location
Massachusetts
Yes it would be good to know and I appreciate all the input from everyone. What would impress me would be if someone could actually teach me about it instead of beating me up saying you should know this or that.

I'm wiling to teach you what you'd like to learn. All I need from you is the specific question you'd like to be taught how to answer. I'd also recommend sharing what you currently understand about the topic, to take an active role in learning it, and so I know where to direct my attention to help you understand.

As an example, suppose you are given this sine wave graph:
371px-Sine-peak-rms.png


You might have a question asking you to find a time instant when the voltage equals half the maximum voltage. Suppose you are given units of Volts on the vertical axis.

You might be thinking, "I can see that its period is 2 seconds, and that its amplitude is 2 Volts. I know this means that I'm looking for a point where the voltage is 1 Volt. But how do I build the equation of the sine wave, and reverse it to solve for time?"
 

Besoeker3

Senior Member
Location
UK
Occupation
Electrical Engineer
I'm wiling to teach you what you'd like to learn. All I need from you is the specific question you'd like to be taught how to answer. I'd also recommend sharing what you currently understand about the topic, to take an active role in learning it, and so I know where to direct my attention to help you understand.

As an example, suppose you are given this sine wave graph:
371px-Sine-peak-rms.png


You might have a question asking you to find a time instant when the voltage equals half the maximum voltage. Suppose you are given units of Volts on the vertical axis.

You might be thinking, "I can see that its period is 2 seconds, and that its amplitude is 2 Volts. I know this means that I'm looking for a point where the voltage is 1 Volt. But how do I build the equation of the sine wave, and reverse it to solve for time?"
I admire your tenacity.........................:)
 

Scottywatt

Member
Location
Mass
Occupation
Electrician/ Construction
Yes that's helpful but all they did show me was a box with a wave no reference points at all in box But a set of number or symbols outside the box on the bottom They were asking how much time it took to get to the half way point and then another question same box asking time at another point on the bottom was something very small outside the box that said I think Div/.011
Maybe a co-sign symbol or a w I don't remember exactly


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