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Old 10-04-2009, 06:12 PM   #1
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Default Practace exam

http://eta-i.org/practice_exams/ceta...ractice2_c.htm

if u got time, how good of a grade do u get?

this is a practice exam i have been doing for a few days, to get ready for my CET in Electronics.
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Old 10-04-2009, 06:32 PM   #2
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Default Re: Practace exam

I answered the first question right. Not willing to do ninety-nine more.

Quote:
It is desired to raise the power to a speaker from 15 W to 30 W. This is a:
  1. 2 dB increase
  2. 6 dB increase
  3. 15 dB increase
  4. 3 dB increase
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Old 10-04-2009, 06:33 PM   #3
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Default Re: Practace exam

^ Is it a 2dB increase?
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Old 10-04-2009, 06:34 PM   #4
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^ No.
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Old 10-04-2009, 06:37 PM   #5
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Default Re: Practace exam

I fail. I studied dB for probably 2 days out of my entire life. I couldn't quite remember the formula, except for that it involved exponentials. As wikipedia tells me, it follows:

L(dB) = 10 log (P1/P0)

In this case: 3dB.
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Old 10-04-2009, 06:38 PM   #6
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^ Yep.
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Old 10-04-2009, 06:40 PM   #7
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Default Re: Practace exam

^ (by the way, I really like this shorthand) You really have your audio down, eh?

...Gotta spread it...
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Old 10-04-2009, 06:44 PM   #8
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Default Re: Practace exam

I was originally mistaken. A 10 dB increase is perceived to be twice as loud. 3 dB is usually a basis to provide headroom when you purchase an amplifier. To increase your headroom by 3 dB, you'll need to double the amount of watts you're putting out. If you want to increase your headroom by 10 dB, you'll need ten times the power.
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Old 10-04-2009, 07:07 PM   #9
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Default Re: Practace exam

basically, when watts is doubled, or reduced by 2, it is considered a step up or down, of 3db
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Old 10-04-2009, 07:19 PM   #10
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Default Re: Practace exam

The noise level in a radio receiver is generated mostly in the:
A. IF stages.
B. RF section. (CORRECT ANSWER)
C. Local Oscillator.
D. Audio section.

I got this 1st one right and stopped after looking at my second question...
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