ohm's law, and 555 question

[Eduardo Saponara]

to calculate the resistance of a circuit,  is it only the resistors and
potentiometers values that I need to add, or do LED's and other things have
to be added in somehow (how do you get their values).

I have been looking at 555 astable circuits as a clock source,  and I am
wondering what V+ Potentiometer  needs to go in on pin 5 to control tempo.
also, anyone know how to get a pulse from it (high time shorter than low
time) ?

all help is greatly appreciated..

thanks