Log problem: In an amplifier, the power gain P is given by
the function:

Question

Log problem: In an amplifier, the power gain P is given by
the function:

hjkhjkhjkhjk · Answer

attachment

jhonyy9 · Answer

Pout
P = 10log ---
                Pin 

10 = 10log 7/Pin 

do you know the logarithms properties ,formulas ?

hjkhjkhjkhjk · Answer

I solved it but I didn't find any of the answer choice, though 3 was the closest.

jhonyy9 · Answer

like for example 

log a +log b = log a*b

hjkhjkhjkhjk · Answer

yes

jhonyy9 · Answer

so in this exercise case log 7/Pin = ?

jhonyy9 · Answer

or than you like 

log a/b = ?

jhonyy9 · Answer

than you see it above i wrote that 

log a*b = log a +log b

hjkhjkhjkhjk · Answer

yes

jhonyy9 · Answer

so than log a/b = ?

jhonyy9 · Answer

log a*b = log a +log b so 
log a/b = log a -log b 

do you can using it in this your exercise case ?

hjkhjkhjkhjk · Answer

log7 - log pin?

jhonyy9 · Answer

Pout
P = 10log ---
                Pin 

10 = 10log 7/Pin 

yes so will be 

10 = 10(log 7 - log Pin)  and now what can you doing in both sides ?

jhonyy9 · Answer

divide both sides by 10 and so what will get ?

jhonyy9 · Answer

1 = log 7 -log Pin 

yes ?

hjkhjkhjkhjk · Answer

yes

jhonyy9 · Answer

log in this case what base has ten or two ?

jhonyy9 · Answer

@mathmale help me please in this above wrote question bc. when i ve learned this log was base 2 but in this case/time not is sure that has base 2

jhonyy9 · Answer

@IrishBoy123 do you can clarify this please ? - ty .

hjkhjkhjkhjk · Answer

We have to solve for x in 1 = log 7 -log x, right?

jhonyy9 · Answer

yes but you need to know this log has base what ?

jhonyy9 · Answer

bc. you need rewriting this 1 in function of this logarithm

hjkhjkhjkhjk · Answer

If it's base 10 then the answer is  0.7 watt.

jhonyy9 · Answer

so than this will be a right choice ?

jhonyy9 · Answer

1 = log 7 - log x 

log x = log 7 - log 10 

log x = log 7/10 

x = 0,7

hjkhjkhjkhjk · Answer

They don't specify which base.

jhonyy9 · Answer

ok. than i remember it right somtime said me here in OS that log mean base ten but how i said above when i ve learned with 40 years ago this was base 2

jhonyy9 · Answer

hjkhjkhjkhjk do you can writing please the choices ? probably from there we can deducting what may be the base of log

irishboy123 · Answer

for this stuff, it's usually base 10

hjkhjkhjkhjk · Answer

Thanks that makes sense

jhonyy9 · Answer

ok. was our pleasure 

good luck 

bye bye

hjkhjkhjkhjk · Answer

Here are the answer choices:

a. 0.7 watt
b. 1.43 watts
c. 3 watts
d. 70 watts
e. None of the above

jhonyy9 · Answer

ok. this now make sens and will be the choice a. right sure 

hope you agree it irishboy

irishboy123 · Answer

ah!

we agree a) !!

well done chaps :-)