there's also a safety factor here. let's say you use an AC current source capable of 2A (we'll use a test frequency of 1khz). the inductor under test turns out to be 500mH with a DCR of 4 ohms (this would be a rather large coil of course), and the capacitor is a 0.05uf cap with an ESR of 1 ohm. 1khz is pretty close to resonance with these values, and the ESR and DCR values are reasonable. testing with the components in a series resonant circuit yields some interesting (and possibly disastrous) results... at resonance, the voltages across each component cancel, so all that shows up across the circuit is the voltage developed by the resistances (ESR+DCR=5 ohms), or 10V. but the voltage across each component is the result of 2A ac through Xc and Xl, each of which are 3k ohms, resulting in 6kV at the joint in the middle where the cap and inductor are connected.... that has the potential to damage both the cap and the inductor.... that's why it's best to do these tests with a function generator rather than a power source.....