Final answer:
In an AC circuit, an inductor can cause the current to lag the voltage, creating a positive phase-angle difference. The phase angle indicates how much the voltage and current are out of phase, and the inductor is the element that contributes to a positive phase angle in such circuits.
Step-by-step explanation:
The circuit element that has a positive phase-angle difference in an AC circuit is typically an inductor. This is due to the fact that inductors offer inductive reactance to a change in current, causing the current to lag the voltage across the inductor by a phase difference of π/2 radians, which is a quarter of a cycle. As the student is referring to a circuit where the reactance of the inductor is greater than that of the capacitor, it indicates that the circuit is inductively dominant, hence the positive phase angle.
When analyzing AC circuits that contain resistors, capacitors, and inductors, one useful method is to use phasor diagrams. This tool helps to visualize how the EMF (electromotive force) either leads or lags other values such as current. In an inductor, the mnemonic 'ELI the ICE man' can be used to remember that EMF leads the current in the inductor (L), while the current leads the EMF in a capacitor (C).
The relative phase between the current and the EMF in an AC circuit with resistive, capacitive, and inductive elements can be determined by using the current general expression i(t) = I0 sin (ωt - φ), where I0 is the current amplitude and φ is the phase angle. Thus, the phase angle signifies how much the voltage and current are out of phase with each other.