What does the term "reactance" describe in electrical engineering?

The term "reactance" specifically describes the opposition that an electrical component presents to alternating current (AC) due to its capacitance or inductance. Reactance arises because the voltage and current in these components do not reach their maximums simultaneously; instead, they oscillate, leading to a phase difference.

In practical terms, capacitors and inductors behave differently in AC circuits compared to resistors. While resistors provide a consistent opposition regardless of current type (AC or DC), capacitors store energy in an electric field and inductors store energy in a magnetic field, both of which create opposing effects in AC circuits. This makes reactance essential for analyzing and designing circuits that operate with alternating current, where understanding both magnitude and phase relationship is crucial for circuit performance.

Therefore, identifying reactance as the opposition caused by capacitance or inductance is key to understanding its role in AC systems.