┌─── R(100 Ohm) ─ L(8.2 mH) ───┐
└──────signal (5Hz sine)───────┘
Then the result shows that there is almost no difference of voltage phase between resistor and inductor, while the theoretical result says that there must be a difference of $\pi / 2$.
I guess there are some interferences by output signal, since inductance is very small($X_L = \omega L \approx 0.258~\mathrm \Omega$) comparing with $R = 100~\mathrm \Omega$; but I do not know why and how it interferes, or whether there are other affects.
Question. Why there is almost no phase difference between of resistor(2nd graph) and of inductor?(3rd graph)
p.s.: Every team has the same result, and other experiments with capacitor(with reactance $X_C\approx R$) give expected results whence I think it is not an experimental mistake.