Hi guys, is there any way of generating harmonics? Harmonics are
generated by the non-linear loads such as the light dimmer. Besides
light dimmer, are there any more circuitries that can be built that can
produce harmonics at the output?

One more question is that, normally harmonics affect the main power
supply. How should I analyze this distorted signal? Should I get the
waveform from the main power supply?

Hope you guys can give me some opinions and guidances. Thanks.