How does resistance differ from reactance?

Resistance and reactance are both measures of opposition to electric current, but they apply in different ways depending on the type of current. Resistance is a property that opposes the flow of direct current (DC), affecting how much current can flow through a circuit based on Ohm's law. It results from collisions between electrons and the atoms of the conductor material.

Reactance, on the other hand, specifically refers to the opposition to alternating current (AC) due to inductance and capacitance. Inductive reactance occurs in coils or inductors, while capacitive reactance occurs in capacitors. These forms of reactance can vary with frequency, meaning that the opposition changes as the frequency of the AC signal changes.

By stating that resistance opposes direct current while reactance opposes alternating current, the differentiation between the two is clearly highlighted. Understanding this distinction is crucial for electrical engineering, where both types of opposition must be taken into account when designing and analyzing circuits.

The other options contain inaccuracies; for example, resistance applies to both AC and DC currents, while reactance changes with frequency rather than remaining constant. Additionally, reactance can impact circuit efficiency, which contradicts the claim in one of the choices.