I connected a DC power supply (set to 706mV) to a 1kohm resistor as this:
The semantic is like:
However, strange things happen when I use the oscilloscope to view the voltage waveform at point A and B.
Below is what is shown on the oscilloscope - cyan wave for point A and yellow for B:
As you see the two points are all sine waves. The voltage difference between the two waves are always kept at 706mV.
I know the dc power supply is floating (not grounded to real Earth) and the oscilloscope here is (separately) measuring the voltage of the two points relating to the real Earth (because the oscilloscope is natively grounded) And I know that a floating circuit’s voltage related to the real Earth cannot be determined.
Yeh, this way truly the 706mV DC voltage is outputted between the two terminals of the dc supply - But, why is the dc power supply outputting two sine waves (relative to the Earth, one higher and one lower) to maintain a dc voltage? Why not straight output plain DC voltages? Is this for safety? As you can see in the oscilloscope picture above - the two sine waves are having much higher magnitudes related to the 706 mV desired voltage, which looks relatively unsafe though...
Also, I don't understand how a floating equipment can make such a voltage referring to the real Earth - previously I always thought there is a voltage difference from an object that does not touch the Earth to the Earth only when there is static electricity or an unequal amount of + - particles in the object.. Now I'm confused about this too...