To measure the phase angle between the inductor current and supply voltage we used an osciliscope and measured the angle between them. We plugged an osciliscope into the circuit measuring the voltage across a 10ohm resistor and called this a "current monitor". To work out the phase angle between the when I used a 68mH inductor and a 4.7kohm resistor the phase angle was 45 degrees.

The next step was to prove this with theory.

The formula is: tan^-1(Xl/R) I get that because you are doing the impedance triangle. This gives a phase angle of 45 degrees. However, how is this measuring the phase angle between the inductor CURRENT and voltage SUPPY. I would have thought this is giving the phase angle between inductor VOLTAGE and voltage supply not the current. Unless I am misunderstanding some theory that you may be able to explain.

Thanks for the help, any questions please ask.