Practace exam

[sniperviper21]

http://eta-i.org/practice_exams/ceta/AST2007_Practice2_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.

 

[01001010]

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

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

 

[JogaBonito1502]

^ Is it a 2dB increase?

 

[01001010]

^ No.

 

[JogaBonito1502]

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.

 

[01001010]

^ Yep.

 

[JogaBonito1502]

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

...Gotta spread it...

 

[01001010]

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.

 

[sniperviper21]

basically, when watts is doubled, or reduced by 2, it is considered a step up or down, of 3db

 

[AzNVi3t2007]

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...