what is meant by lagging and leading current in ac circuit
Leading and lagging current Leading and lagging current are phenomena that occur as a result of alternating current. In a circuit with alternating current, the value of voltage and current vary sinusoidally. In these types of circuits, the terms lead, lag, or in phase are used to describe current with reference to voltage. Current is in phase with voltage when there is no phase shift between the sinusoids describing their time varying behavior. This generally occurs when the load drawing the current is resistive.
RL circuit These equations show that a series RL circuit has a time constant, usually denoted τ = L/R being the time it takes the voltage across the component to either fall (across the inductor) or rise (across the resistor) to within 1/e of its final value. That is, τ is the time it takes VL to reach V(1/e) and VR to reach V(1 − 1/e).