# NEESC # 537



## Benee (Oct 18, 2010)

Is there any one having a problem for # 537? The math part and the solution don't agree to each other. Per the Capacitance of the transmission line equation. If Rc increase, then the Capacitance will get larger. However the solution state " if Rc increase, the Capacitance of the Transmission line to ground decrease" ? Again I just based an the math. Maybe there is some exception rule that I don't know. If any one know please let me know


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## LMAO (Oct 19, 2010)

Benee said:


> Is there any one having a problem for # 537? The math part and the solution don't agree to each other. Per the Capacitance of the transmission line equation. If Rc increase, then the Capacitance will get larger. However the solution state " if Rc increase, the Capacitance of the Transmission line to ground decrease" ? Again I just based an the math. Maybe there is some exception rule that I don't know. If any one know please let me know


You are right; there is a mathematical error in the answer. if you increase rc, C will also increase. BUT C is not "directly proportional" to rc so even though the explanation of answer is wrong, the answer itself is right.


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## knight1fox3 (Oct 19, 2010)

The Errata for the 2009 PE power exam covers problem 537.


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## Benee (Oct 19, 2010)

LMAO said:


> Benee said:
> 
> 
> > Is there any one having a problem for # 537? The math part and the solution don't agree to each other. Per the Capacitance of the transmission line equation. If Rc increase, then the Capacitance will get larger. However the solution state " if Rc increase, the Capacitance of the Transmission line to ground decrease" ? Again I just based an the math. Maybe there is some exception rule that I don't know. If any one know please let me know
> ...


Thank you very much, The key world is "directly Proportional". Without your help, I will bang my head to the wall arty-smiley-048: arty-smiley-048:


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## Benee (Oct 19, 2010)

knight1fox3 said:


> The Errata for the 2009 PE power exam covers problem 537.


Thank you very much


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## cruzy (Oct 23, 2010)

So what does directly proportional exactly mean? By their answer, I take that to mean when one value increases (or decreases), the other value also increases (or decreases). So what is it called when one increases while the other decreases?? Inversely proportional??


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## cruzy (Oct 28, 2010)

Never mind my above reply. I didn't think about the diameter being a function of a sqrt., which makes it not directly proportional. I coulda sworn that I keep reading in places where it says "...........is directly proportional by the square of (or square root)....." Maybe they are missusing the phrase directly proportional as well. Man I didn't think we're taking the BAR exam here.


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