Basic electrical theory

[LarryFine]

No. What is really stupid is when you get the first of the two correct, but get the second one wrong because you think it must be a trick question. I would have had 100%

I feel your pain.

 

[joebell]

Retired as of Sep. 09

It's easier to get a BA then a Jy lic

BEE AE A school Jax Fla. 1970. basic review of HS but it left time for liberty. in St Augustine

BEE Orlando CE A school Gulfport MS. Enjoy retirement

 

[zog]

zog, I went thru an apprenticeship program (which I thought was great) although at the time, I didn't think I'd use the theory like I actually do. There have been some great posts on voltage drop and other calcs here on the forum that I have printed out for the guys to take home for homework. They have not had basic theory and one gentleman in particular is enamored with it, as it puts a how with the why, or the other way around. I think we all should have basic theory. I don't know that I would get by without it in the field. There were, however, some navy guys in my class and they already had it down pat!

I taught lots of different classes to industrial electricians for 15 years, and I always packed a bunch of theory stuff in there. I would say 90% of them had no idea what I was talking about but 75% of those who didn't were very eager to learn it and happy that someone was finally explaining it to them.

Of coure, industrial electricians are different animals than EC's.

I also was a master trainer for the navy nuclear power program and taught electrical theory to navy nuke electricans, officers, and civilian (DOE) personel.

 

[growler]

To become a "Certified electrican" do you ever have to learn basic electrical theory? I don't mean this question in any demeaning way, I just don't know the answer. http://

You don't even have to learn basic electrical theory to be an electrical engineer. I'm sure they should at some point learn basic electrical theory and some how they did manage to pass some tests in order to graduate but "some" sure as heck didn't understand it ( I'm only talking about a few select individuals that I know of, not all engineers, one in particular comes to mind). For some reason there are those in all professions and trades that make it through training and testing without actually learning anything.

Certification only means that you have met a given criteria, normally experience or training and being able to pass some sort of test. It really depends on just who is doing the certification and how strict they wish to make the requirements.

90% of doctors didn't graduate in the top 10% of their class.

 

[Ken9876]

There was almost no theory taught in the classes I took.. Luckly the instructor I had covered some theory, however the other instructor that taught the other first year class didn't feel it was needed. I think it was a requirement that theory was taught because they followed some federal standard. I think it really should be covered as all the other pieces will fall together and make sense if you know the theory.

In the place I work a young guy had asked a question one time, and the other guys just made fun of him, I took the time to show him the answer. I feel that is pretty much how it is everywhere.

 

[zog]

In the place I work a young guy had asked a question one time, and the other guys just made fun of him, I took the time to show him the answer. I feel that is pretty much how it is everywhere.

I see that all the time, every place I have worked there were the same kinds of guys, ones that wanted to learn it but were afraid to ask because they would be made fun of and the morons that thought they knew it all (But didn't) and made fun of them.

I have always taken the time to teach theory, after hours on my own time, mostly to the young guys. I have a 40 hour basic electrical theory presentation that I break up in small sections.

I am in power system testing, the problem is the new test equipment is so automated you don't need to do much so you can skate by with weak theory until something goes wrong. I have always made the new guys use the oldest most basic test equipment we have, takes twice as long to test stuff but you really have to understand what you are doing, where you are injecting current, etc..

 

[nakulak]

You don't even have to learn basic electrical theory to be an electrical engineer. I'm sure they should at some point learn basic electrical theory and some how they did manage to pass some tests in order to graduate but "some" sure as heck didn't understand it ( I'm only talking about a few select individuals that I know of, not all engineers, one in particular comes to mind). For some reason there are those in all professions and trades that make it through training and testing without actually learning anything.

I didn't graduate as an EE, but I started out as one, and electrical theory was the first real EE course they gave us. I am sure that is true for most EE programs. What they don't necessarily teach (if you don't take it) is practical applied power wiring as its done in residential and commercial, and the NEC and how it is applied. I think that's why its required to work under a PE for a while in order to give give green EEs a chance to learn proper field applications of what they do.

I have however worked with plenty of electricians who could not theorize their way out of a paper bag. I worked for a master electrician who did not know the difference between a series ckt and a parallel one, and it suprised the hell out of me.

I have also seen that, while apprenticeship school around here does seem to teach the guys a bunch of stuff, and entices them to learn more, it sorely lacks the level of theory necessary to turn these guys into a basic trouble shooting technician. I think it would be a great thing if they changed the program and made it 5 yrs, and devoted one year to strictly circuit theory.

just my 2 cents

 

[TOOL_5150]

Other than a little dinky electrical class in high school, I am self taught and learned hands on from others. I passed that test, but need to brush up on some things.

I thought the 2 questions about columb's theroy were trick questions, so I missed the 2nd one.

~Matt

 

[gar]

091212-1750 EST

I took the test as a closed book test and got the same result as LarryFine and for the same reason. It is a very long time since Coulomb's law and the inverse r^2 force relationship were linked together in my mind.

So I looked in two old school books and neither indexed Coulomb's anything. Both these books were primarily related to electric and/or magnetic fields. One was "Fundamentals of Engineering Electronics", by William G. Dow. This is largely on vacuum tube theory (space charge). The other book was "Electric and Magnetic Fields", by Stephen S. Attwood. Even though unindexed he did discuss Coulomb's law. From Attwood's book.

The law of electrostatics is Coulomb's law which states that two electric charges of like sign repel each other (and unlike charges attract each other) with a force which is proportional to the product of the charges and varies inversely as the square of the distance between them. ----
Consequently, unit charge (the coulomb) is one that repels a like charge in a vacuum at a distance o 1 meter with a force of --- This is an enormous force, equal, very approximately, to 1,000,000 tons. ---

I did remember one problem from Dow's book, but obviously not the complex details:

A particle of mass 3me and charge 2qe is accelerated through 900 V, then projected into a uniform magnetic field of flux density B, at 30 degrees with the Z axis, 90 degrees with the Y axis, see Fig 2.20. B is perpendicular to the YZ plane. A brass plate having a small hole lies parallel to the YZ plane. The hole is 10 cm from the XY plane and the XZ plane. Find the flux density B, and the distance from the YZ plane to the plate, that will make the particle go through the hole.

I would have to do a lot of review to do that problem now. Basically the particle is following a circular path perpendicular to the magnetic field, but there is an initial velocity component parallel to the magnetic filed and therefore a spiral path is generated.

Another interesting discussion in Dow's book that relates to discussions that have occurred on this forum is in a chapter on Amplifier Circuit Principles:

The term "resistance" as applied to a nonlinear circuit element, may have a variety of meanings. e/i (volts divided by amperes) may have one value, watts/i^2 another, and de/di still another, although for an ordinary resistance all three have the same value. In many nonlinear circuit elements, and especially vacuum tubes, the currents are usually pulsating, consisting of a-c components superimposed on d-c ones. When the a-c components of voltage and current are relatively small, the ratio between them is de/di, which can therefore be called the a-c resistance of the element."

There were at least two questions on the test of post #1 where the wording was something like "current across resistor R1" instead of "current through resistor R1".

.

 

[ohmhead]

I am wondering, because I learned the trade in the military where theory is the base of everything.

To become a "Certified electrican" do you ever have to learn basic electrical theory? I don't mean this question in any demeaning way, I just don't know the answer.

For example:
Series and paralell circuit calulations
Power equations for the 3 types of power
Use of basic test equipment

For example, click here and take the basic electricity test. I think everyone should be able to pass this basic test.

http://www.avotraining.com/avo-assessment-tests.php#BasicElec

Well Zog i guess from what ive seen thur the years as a electrician most abc schools and union jatc do not teach enough theory i was a EM navy plank owner CVN NIMITZ 68 .

Good school basics and aboard ship out at sea we could attend on our own more advanced training by Westinghouse engineers who came along for the ride ac & dc theory / power generation/ motor / advanced electronics/controls / semiconductor theory / reactor/ turbine steam generation / dc motor gen/ rectifiers / But ive never stopped learning to this day i read about all the new electrical innovations i must know how it works and why it works .

We all come from different areas and places but iam in electrical construction we do plants / industrial/ commercial/ only
The jobs we do are 25 million plus electrical theres lots of theory in planning that .
You dont do our pipe work just out of school it takes years of training in the field so you must understand were not just construction electricians as most people think .

As far as industrial electricians been there and my job is tuffer now than then that was easy work ive tested lots of breakers in the navy and did a fair share of repair work 16 hours a day in 30deg below cold weather on cold steel you can have it .

 

[hambone1216]

I'm a fourth year apprentice and theory is in all your sit down class time, but it is only used in repetition concerning calculations ex. Ohm's law, turns ratio's
The troubleshooting is where i have found it most useful. If you cant look at a schematic drawing and follow the path of electricity how you going to know where to start testing and what values you should have?

 

[knoppdude]

I'm a fourth year apprentice and theory is in all your sit down class time, but it is only used in repetition concerning calculations ex. Ohm's law, turns ratio's
The troubleshooting is where i have found it most useful. If you cant look at a schematic drawing and follow the path of electricity how you going to know where to start testing and what values you should have?

This hits the nail on the head. IN my apprenticeship, I found that most, but not all journeymen that I worked for, did not think understanding theory was necessary to be an electrician. In addition, the classroom study involved reading and answering questions. After I turned out, I took a two semester theory course at a local community college. It covered theory, and had hands on labs. Attending that course was something I have never regretted. When prospective employers threw their tests at me, what I learned often got me a job, as well as made the actual electrical work easier to understand when it required trouble-shooting.

 

[ggonza]

I'm in my third year of apprenticeship classes right now, and I feel like I understand The basic theory well enough to get by. But I feel like My curriculum didn't sress the importance of anything that would really help me to stand out. I mean we spent 2-1/2 months on single phase transformers. 2-1/2 months! With the same questions on our homework every night with just different numbers. It must be part of the "no child left behind" plan. And after all that I was helping a journeyman install a 240/480pri-120/240sec single phase transformer. And if you can believe me, he actually said " Now I'm no transformer expert, but I don't see an XO anywhere." (pause for laughter).I'm sorry I hope I don't sound too negative, I just know that our discussion on Harmonics consisted of about 5 sentences out of a book. And our instructor couldn't answer any of our questions. I think there was some students in there that went home that night thinking that harmonics were a good thing to have. I know I can't have an intelligent discussion about them. Awhile ago my wife's granfather asked me what I was learning in school, I told him motor theory. We talked a little bit about that, and then he asked me about resonance. Apart from my "deer in the headlights" look I must have looked like an idiot, because up until that point I thought I had been keeping up okay. Anyways that's just my feelings about the school I attend I hope it's not like that everywhere else.

 

[electricalperson]

i believe an electrician needs a good understanding of electrical theory. it seperates the electricians from the installers.

 

[skeshesh]

Great discussion. I'm a BSEE I was thinking about going for a MS but boy am i glad I decided to get a few years of work experience first. By the time I go for the MS i'm gonno know exactly what i'm trying to learn. I agree with all the comments regarding lack of practical stuff at the universities. I had to take so many random general ed. courses I cant help but to hate the department for not allowing for just one course that glances over the code/practical considerations/cost estimation/contracting and all the other stuff you need to know to be a proper engineer. Finally I agree ignorance of theory runs in all fields and levels of the business - a lot of engineers do cookie cutter design. Just last week I heard one of my coworkers (60+ old electrical engineer) tell answer someone's question regarding kW/kVA by saying "it means you multiply it by 0.85"...

 

[zog]

Just last week I heard one of my coworkers (60+ old electrical engineer) tell answer someone's question regarding kW/kVA by saying "it means you multiply it by 0.85"...

When I get that close to retirement I will probally say the same thing, easy short answers, don't bother me, I am napping.

 

[gar]

091215-2234 EST

It is very unfortunate when discussions and the meaning of words are are distorted such that their meaning becomes muddied.

On the subject of Ohm's law here on some quotes from Francis Jehl's book "Menlo Park Reminiscences". These comments generally relate to electrical knowledge circa 1879. These are from chapter XLVII, and provide an indication of instrumentation and known techniques of that period. Very shortly after this there were great advancements. Basically these comments indicate that Ohm's law was C = E/R. Nothing to do with the power equation. You will see the means of measuring current was by electrodeposition if you read Jehl's book.

But before proceeding with Jehl look at these Internet sites:
http://electrical-engineering.suite101.com/article.cfm/watts_law
http://www.hasdeu.bz.edu.ro/softuri...ite/further_info/further_info_8_biography.htm
http://www.makingthemodernworld.org.uk/people/BG.0096/
A quick Internet search does not provide more specific information about Joules's determination of the electric power equation.

Dictionary.com defines joule as "a unit of electrical energy equal to the work done when a current of one ampere is passed through a resistance of one ohm for one second." James Prescott Joule, an English physicist, recognized this relationship and derived an equation from Ohm's Law describing power (P) as the product of voltage (V) and current (I), or P = V * I.

Note: that Jehl was an assistant to Edison in the development of the electric lamp and power system. The following quotes are from his book.

We acknowledge our debt in electricity to the labors of Davy, Ohm, and Faraday; Joseph Henry had a hand in it too. Among these great men I place George Simon Ohm upon the most elevated pedestal; for his equation C=E/R governs every fundamental in the electrical workshops of the world. Ohm's law is the most valuable asset that modern electrotechnics possesses; it is the very essence of electrical economics.

Ohm, and insignificant schoolmaster, was derided when he expounded his law in 1827; it seemed too simple.The high-hatted mathematicians were outraged that a plain schoolmaster should offer a simple equation to bring out a law governing the antics of the mysterious fluid. Scientists had later to accept his law; for it was truth.----

You really need to read this book to get an understanding where the electrical field of knowledge was in 1879.

--- It took a long time to recognize and substantiate the correctness of his (Ohm's) conclusions, as also to know how to apply the law and to be satisfied that all the vagueness concerning the relation between current, tension, and resistance had vanished. Though we possessed standard ohm resistances and Wheatstone bridges, could measure infinity low or high resistances, and could make a shunt of known resistance, yet we did not know a single simple method of determining current. We possessed standard batteries with which, using Thomson's high resistance reflecting galvanometer, we could likewise determine tension (or voltage). Thus we had an easy and practical way the units of resistance and tension (probably should have added the words --- could be measured). Yet no one had the common sense to tell us how to get the current. No budding thinker appeared on the horizon to tell us to measure the resistance of a part of the wire through which the current flowed, and then take the drop of potential on that known resistance, all of which could have been most easily done. With E and R given, the other unit, C, would have appeared. In other words it simply amounted to taking a known shunt and the drop of voltage on it.

Even in 1880 theorists were behind as regards the value of Ohm's law. ---

This illustrates the state of electrical knowledge at this time. What is so obvious today was not at that time.

The measurement and relation of power to E and I was not known then and is not part of Ohm's law.

.

 

[gar]

091215-1315 EST

The meaning of my last sentence is not very clear. The word "then" relates to the time, 1827, when Ohm created his equation, not to 1879.

Joule's law, P = I^2*R, was created in 1841 according to Wikipedia.
http://en.wikipedia.org/wiki/Joule's_laws

Ohm's and Joule's laws are different and evolved from different experiments and reasoning. One can use Ohm's equation, or different iterations of it, to generate different forms of Joule's law.

.

 

[skeshesh]

When I get that close to retirement I will probally say the same thing, easy short answers, don't bother me, I am napping.

It's different from person to person. If you asked my dad the same question (62 years old, top notch electrical eng. consultant) he'll probably go on and on explaining till you beg him to stop. I guess when you love what you do...

 

[MKWW]

I got a 70% and I'm a carpenter.