re: "... ohm's law implies that a current of 12 V/300 Ohm = 0.04 A
will flow ..."

No!  It doesn't "imply".  It's the LAW!

Sorry.  Couldn't resist.

//Jack

On 13 Nov 2003, at 16:59, Daniel L. Katz wrote:

> list:
>
> kindly note that current and voltage are not independent, and that 100 mA
> through the heart for 1 s would probably be fatal.
>
> in the simplest cases, current and voltage are related fairly precisely
> through ohm's law:
>
> I = V/R
>
> where I = current and V = potential difference across R. for example, if 12
> volts is applied across a 300 ohm 1 W resistor, ohm's law implies that a
> current of 12 V/300 Ohm = 0.04 A will flow through the resistor. it makes no
> difference whether we say the voltage is 12 V on one side of the resistor and
> 0 volts on the other, or 1,000,012 volts on one side and 1,000,000 volts on
> the other, we get the same 12 V potential difference across the resistor, and
> the same amount of current, 0.04 A, will flow. in this case, the power
> developed by the resistor would be 0.48 watts, within its 1 W power rating.
> now, what if we substitute a 30 ohm 1 W resistor instead? well ohms law would
> predict a 0.4 A curren and heat produced at the rate of 4.8 W, nearly 5 times
> the power rating of the resistor; in this case, ohm's law does its job in so
> far as letting us know that the resitor would fry, but the resistor itself
> would change value significantly as it burned up.
>
> dlk
>
>
>
> >The charge LED flashes fine even in pretty low light, but it's only
> >indicating that there's voltage present... however there's nearly no
> >current, and it's current, not voltage, which will charge a
> >battery... or an electrocution! (a 100mA current of 1,000,000V will
> >not even be felt).