"Bart Bervoets" wrote in message
...

are fairly constant. You didn't indicate what sort of
device you are trying to power; some are much more forgiving than others.

Creative labs pc speakers in my car.

So you need a 3 ohm 5 watt resistor

And for 2 amps?
I don't really understand your calculation as i am useless in math.

Forget it, a resistor is useless for your application. You'll need to build
a decent voltage regulator circuit to power such gear if you want it to
work well.

You may find the speakers work just fine at 12V ( or more like 13.8V or
higher if we're discussing a car's power supply), it's up to you whether you
want to risk finding out!

Dave