I used a series RC circuit in the experiment.
In circuit one, I had sine signal to resistor to capacitor to ground.
Then, I had Vs and Vc in scope. I got the phase difference,p1.
In circuit two, I exchanged the positions of resistor and capacitor.
So, I had sine signal to capacitor to resistor to ground.
Then, I had Vs and Vr in scope. I got the phase difference,p2.
p1+ p2 is approximate to 90 degrees.