It seems natural to you to deal with voltage as your base since that's
how electronics is taught.  Today's electronics revolve around constant
voltage sources, a/d measurements are always voltage level measurements,
etc.

However, there's a whole world of electronics where current is used as
the 'base' and voltage is not emphasized.  There are some applications
where current is easier to use, such as the common current loop
industrial controls, rs-422 (IIRC, a current loop serial port), etc.
It's not difficult to take a simple constant voltage circuit and convert
it to a constant current circuit.

In fact, current is one of the reasons so many people shie away from
analog electronics.  Some circuits are /exceptionally/ difficult to
analyze from a voltage point of view, but are practically trivial from a
current point of view.  And thanks to this dandy equation it's easy to
find the voltages once you've solved the circuit for current.

Transisters and op-amps both work based on currents.

-Adam

Rick Regan wrote:

>>But I is only the dependant variable in *one* way of
>>looking at it. V=IR is the appropriate way of writing it
>>if you consider ohm's law to mean " V = the voltage drop
>>across resistance R with current I passing through it".
>>You can come up with a similar, equally valid phrase,
>>for the third way of writing it out (r=v/i).
>>
>>
>
>But aren't R and V the only two of the three variables
>that you can manipulate directly?  I depends on these,
>right?  I think writing it I=V/R would be less confusing
>to the novice.  With the V=IR form, I've seen
>descriptions like "if the current doubles the voltage doubles."  Mathematically, yes, but it's not like you can
>double the current independently of V and R.
>
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