Final answer:
In AC circuits, an inductor exhibits a negative phase-angle difference due to the current lagging the voltage by 90 degrees, which adheres to Lenz's law, stating that the induced emf opposes the change in current.
Step-by-step explanation:
Circuit Elements with Negative Phase Angle
A circuit element that exhibits a negative phase-angle difference in an alternating current (AC) circuit is typically an inductor. The phase angle in AC circuits represents the amount by which the voltage and current are out of phase with each other. In inductive reactance, which is the opposition of an inductor to a change in current, the current lags the voltage by π/2 radians, or 90 degrees. According to Lenz's law, this opposition means that the induced electromotive force (emf) within the inductor acts to oppose the change in current, leading to a negative phase angle between the current and the induced emf.
For example, when the current in an inductor is increasing, the induced emf will act to oppose this increase, resulting in a current that lags behind the potential difference across the inductor. This is represented on a phasor diagram by a phasor that rotates counterclockwise from the voltage, indicating a lagging current. A negative phase angle is thus associated with inductors in AC circuits, which is significant because it determines the direction of power flow and affects how different circuit elements interact.
The mnemonic device of "ELI the ICE man" helps remember that the emf (E) leads the current (I) in an inductor (L) and the current (I) leads the emf (E) in a capacitor (C). When analyzing a circuit with both capacitors and inductors, along with resistors, it is important to consider these phase relationships to accurately determine the overall emf of the circuit by using phasor diagrams.