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04-13-2012, 3:17 PM
 Member Join Date: Sep 2010 Posts: 10
Help with General class question

Can someone help me understand why the answer I selected is not correct...?

First I determined the current using Ohm's law:

E = IR
I = E / R
I = 400VDC / 800R = 0.5A

Then the power:

P = IE
P = 0.5A x 400VDC = 200W

Last edited by Sparkletron; 04-13-2012 at 3:45 PM..
04-13-2012, 3:35 PM
 Member Join Date: Dec 2006 Location: Oklahoma Posts: 1,647

Nope, I can't explain why your answer was wrong. Using (I^2)R yields 200 watts, like the W=IE equation. What are they asking for if not the answer to one of those formula?
Is this a multi-part question?
- 'Doc
04-13-2012, 3:42 PM
 Member Join Date: Sep 2010 Posts: 10

According to the practice test at QRZ, the correct answer is: 32000W. I have a feeling it's just a mistake with their testing application. The exact question is: G5B03.
04-13-2012, 3:45 PM
 Member Audio Feed Provider Amateur Radio Join Date: Jan 2010 Location: Modesto, CA Posts: 1

Your answer is correct. I just tried it on QRZ and it showed the right answer. Maybe it was a glitch in the program.
04-13-2012, 4:12 PM
 Member Join Date: Sep 2010 Posts: 10

Thanks for responding. Good thing this was an answer I was confident in. With some of these questions, I'll accept anything they tell me ;-)
04-18-2012, 2:33 AM
 Member Amateur Radio Join Date: Mar 2004 Location: Virginia Beach, VA Posts: 840
Good thinking!

Since we're allowed up to 1500 watts pep on most bands, it wouldn't seem logical that the correct answer would be a power level we would not legally be able to operate. I would have eliminated that one before doing any math.
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Steve KC4JGC
04-18-2012, 10:40 AM
 Member Premium Subscriber Amateur Radio Join Date: Jan 2012 Location: Cincinnati, Ohio Posts: 209

When I ran the practice questions on the TECH class using the Technician License Maunal published by ARRL, I also found a few questions where I thought there was a bug, either in the Software, OR in in the actual database regarding the "correct" answer. I can't remember which ones they were now, but one did involve a Resistance and/or power calc, That I remember. Also, there was a question where I think it flagged the incorrect answer as correct on a decibel gain question, or something like that...

Not too many ways to screw up V=IR and P=VI.

My money is on a glitch. ... (??)
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GrumpyAeroGuy
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BC235XLT, PSR500
04-18-2012, 10:56 AM

I checked the question pool posted at the National Conference of Volunteer Examiner Coordinators web site and it shows B as the correct answer. Sounds like QRZ is incorrect.
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"The whole world's living in a digital dream. It's not really there, it's all on the screen." -- Joe Walsh WB6ACU
04-18-2012, 1:25 PM
 Member Join Date: May 2008 Posts: 65

I use this site, you can see the explanation there, too.
https://hamstudy.org/browsepool/ques...st/E3_2011/G5B