What is the SI unit of electrical impedance?

The SI unit of electrical impedance is the ohm. Impedance is a measure of how much a circuit opposes the flow of electric current when a voltage is applied, and it is represented in terms of resistance and reactance. The ohm quantifies this opposition in alternating current (AC) circuits, analogous to how resistance applies to direct current (DC) circuits.

Understanding impedance is crucial when analyzing circuits, especially those involving inductors and capacitors, as it encompasses both the resistance due to the material and the phase difference between voltage and current due to reactance. The other options represent different electrical properties: volts measure electric potential, amperes denote current, and watts quantify power, but do not pertain to the measurement of impedance itself. Thus, the ohm is uniquely associated with the concept of impedance in the realm of electrical engineering.