On Jun 14, 2010, at 12:07 PM, Forrest W Christian wrote:

> 1M/10K
>   :
> 100ohm/1ohm.
>
> I would have guessed that the top one is going to charge the  
> capacitor a
> lot slower than the bottom one.... but I'm starting to think that
> perhaps they are all equivalent?   Did I miss/forget something in my
> electronics training?

They're not equivalent.  The top one has an impedance slightly less  
than 10k ohms, and the bottom one has an impedance slightly less than  
1 ohm.  So the top one will charge a cap "a lot slower" than the  
bottom one.  It's just that "most" of the voltage charging the cap  
will come from the 10k leg of the circuit, "plus" a little bit from  
the 1M leg, so it's equivalent to less than 10k overall...

http://en.wikipedia.org/wiki/Th%C3%A9venin%27s_theorem

BillW

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