What is the unit of impedance?

Impedance is the measure of opposition that a circuit presents to a current when a voltage is applied. It is a complex quantity that encompasses both resistance (the real part) and reactance (the imaginary part), which is why it is critical in both AC (alternating current) and DC (direct current) analysis.

The unit of impedance is the ohm, which is the same unit used to measure resistance. The relationship in an electrical circuit is described by Ohm's Law, which states that the voltage across an element is equal to the current flowing through it multiplied by the element's resistance (or impedance in the case of AC circuits). Therefore, impedance quantifies how much voltage is required for a given current to flow, making the ohm a fitting unit to express this concept.

The other options—volt, ampere, and coulomb—represent different electrical properties. The volt measures electrical potential, the ampere measures electric current, and the coulomb measures electric charge. None of these units encapsulate the concept of impedance as effectively as the ohm does.