Hello,
I have an audio amp, 40 watts RMS per channel (8 ohm) and I would like
to plug to one channel a small speaker 19 watts (8 ohm).

4 questions:
1- What circuit should I build to adapt?

2- How can I know how much ampere the amp is using to drive one
loudspeaker?

3- A better suitable newsgroup to post this question?

Search on the internet:
4- What words should I use to find some appropriate technical texts?

Thank you.