When alternating current flows through an inductor voltage leads current by a phase angle of 90 degrees what is the physical interpretation of this phenomenon?

Answer 1

The physical interpretation of voltage leading current (by 90o) in an inductor is just that. The instant voltage is applied, the inductor "feels" the applied voltage and responds by "beginning to generate" a reverse voltage (reverse electromotive force or emf, or back emf) which prevents current from flowing for the first instant of time. At time zero, the inductor is infinitely resistive. As time goes on, current is increasing. It is trying to "catch up" to voltage, which is continuing to climb. The back emf is trying to limit current, but it climbs to try to "follow" the increasing voltage. But voltage peaks and starts down. The magnetic field that was building while voltage was climbing (and was "holding back" current flow at the same time) will begin to collapse. The collapsing field generates emf that will try to keep current flowing, so current will continue to increase while voltage is decreasing. The current peaks later on (like 90o later) and then starts to decrease. In a purely inductive circuit to which AC is applied, the current is "chasing" the voltage peaks and is always 90o degrees behind. [There are other ways to look at the situation, but this one is a basic way to interpret the physics.]