DIYbanter - View Single Post

Smitty Two

In article ,
(Doug Miller) wrote:

If you want to limit the current passing through an LED, you put a resistor
in
*parallel* with it, not series.

Surely you jest. The resistor absolutely goes in series.

I've read so many erroneous claims in this thread I hardly know where to
start setting the thing straight. In a purely resistive circuit, whether
it's AC or DC, ohm's law rules. You cannot possibly change one without
affecting another.

For example, a long length of wire supplying a light bulb adds
resistance to the (series) circuit. The first thing this does is reduce
the circuit current, by increasing the total circuit resistance while
the supply voltage remains constant.

The second thing it does (simultaneously of course) is *split* the
supply voltage between the wire and the light bulb. So the intended load
(light bulb) gets less voltage. Some of the voltage is dropped (lost)
across the resistance of the wire.

Like Arnold, "I'll be back," but I've had trouble posting these last few
days due to ISP issues, so am limiting my postings severely in order to
stay connected at all.