Re: Power - brainteaser


"CWatters" <colin.watters@xxxxxxxxxxxxx> wrote in message
news:sAikf.63465$mf2.3599417@xxxxxxxxxxxxxxxxxxxxxxxx
>
> <jvereker@xxxxx> wrote in message
> news:1133603022.647250.144540@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>> Hi,
>>
>> I got the following brainteaser I can't handle with: what power we'll
>> get on a resistor powered from 100W amplifier set on the level -40dB,
>> when the source is a CD-player producing white noise at level -36 dB ?
>> What current flows thru that resistor ? We assume, that all the
>> circuits are linear.
>
> If I remember correctly...
>
> 0dB would be 100W and you have -76dB
>
> so the output is
>
> = 100 x antilog (-76/10)
> = 2.5uW
>
> which sounds a bit low.

0 dB is meaningless as stated here. 0 dBm would mean 1 mW is the reference
level.


.

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