Ok, the wiki link is french to a chemical engineer like me. In a receive or amplifier, why and where is it generated. Also is it correct that if I go above 0dB on master volume, there will be a lot of distortion?
Incorrect again!
The volume control has nothing to do with the power output in absolute terms. There are too many variables. The input voltage from the source will vary, even from one CD to another. The speakers you own is the other variable as they will draw power as determined by their sensitivity and impedance curve. For instance most receivers put out max power into 8 ohms. If the speaker is 4 ohm, especially in the power hungry range of between 60 and 500 Hz, then most receivers rated at 100 watts are only 50 watt receivers under those conditions.
Major distortion, clipping, will occur when the amp is asked to provide more current and or voltage into a load than it can supply. The exact position of the volume control where that occurs is impossible to predict.
A lot of receivers generate pink noise for level set and calibration.
My advice to you is to stop worrying about this, set your volume control to a comfortable level and enjoy!
However as you are a chemical engineer you must have significant understanding of concepts encompassed in the discipline of physics, other wise I fail to see how you could be a competent chemical engineer. Therefore if you want to study these and other issues in greater depth you will make faster progress than the average member, I would hope.