Thevenin and Norton

[stevenal]

http://www.doonesbury.com/strip/dailydose/index.html?uc_full_date=20060504

http://www.doonesbury.com/strip/dailydose/index.html?uc_full_date=20060510

The question is: Am I the only one who thinks Alex, the Cornell professor and G.B. Trudeau seem to have missed the whole point of Thevenin and Norton equivalent circuits?

 

[IRstuff]

Why is that meaningless?

Is it any more irrelevant than figuring out the threshold voltage of a TTL input? Which the applicant failed to answer THREE times, where he was shown the answer after both the first and second times?

TTFN

 

[itsmoked]

Ha! Good point IR.

After learning the Thevenin and Norton stuff I have never ever used it. Pish-shaw!

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[OperaHouse]

I made up a test to give to perspective technicians at an interview. Every one of the applicants said they worked from schematics and repaired boards at a component level. It was 20 questions with four multiple choice answers. Simple things like he would find in the job. Example; A transistor with .75V on the base of a transistor 0V on the collector sinking current from a LED. LED is not on and 12V is on the otherside of it is 12V. We have a lot of LEDs that get put in backwards. Another id a voltage on a resistor and figure out the current, nice even number stuff.

Where you could get 25% just by chance, I found a score of 35% was a good candidate. Some people ran out of the room. The only one that ever passed it said he wouldn't work at such an idiotic place. I had to reduce the test to 4 questions because they were taking close to an hour to answer 20 simple questions!

 

[itsmoked]

OperaHouse; Ah, that is some choice stuff there!

I once took a test for the electrician's union placement. I aced the math and was in the top 5% for the the ridiculous "draw lines between the lines" of hundreds of concentric circles with both hands at the same time. Some sort of mind numbing dexterity test. Then I got to the verbal. After we all laughed about the my then recent news worthy arrest for driving around my town and over some hundred foot trestles on the railroad tracks they asked me how badly I wanted to be an electrician. I said I wanted to actually be an Electrical Engineer.. That was a conversation stopper. Hahaha . We all decided I shouldn't bother with the electrician path.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[zappedagain]

Keith - And the rest, as they say, is history...

 

[bacon4life]

I had just finished my first semester of circuits class, where we of course covered the idea of equivalents. We had also just touched on voltage dependant current sources and current dependant voltage sources. Since we had never combined the two ideas, I figured I could try putting one on the equivalent circuit. Maybe an active device would react differently than the passive RLC components we talked about in class? It turns out that if you put a voltage controlled current source on the terminals, and then proceed work through some math you can prove the difference as long as you ignore a minus sign on the first step. I figured I had also better also try out a current controlled voltage source, which I was actually did correctly. As I was redoing the math for the first case, the interviewer finally took pity on me an explained about the heat/power cord technique.

I felt really bad, until I went back to my dorm and asked many of peers who were all as stumped as I had been.

 

[billbehen]

The Thevenin & Norton Equivalents are only meant to be equivalent at their two terminal outputs, not necessarily so from the power supply end. One could just as easily claim (correctly) that you could just open the box and look!

By the way, it might confound the line-cord heat analyzers if they were not allowed to "peek" at the two output terminals (fair's fair!) How? Easy. If the two ouput terminals were shorted (the dual of the open circuited case) the Norton Equivalent box would remain cool as a cucumber....