ARRL Technician Practice Exam

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What are the units of impedance?

Volts
Ohms
Amperes
Watts

The correct answer is: Ohms

Impedance in electrical circuits is measured in ohms. It represents the opposition that a circuit presents to the flow of alternating current (AC) and combines the effects of resistance, inductive reactance, and capacitive reactance. When analyzing AC circuits, it is important to consider impedance because it determines how voltage and current interact through various elements such as resistors, capacitors, and inductors. In this context, volts are the units of electric potential, amperes measure electric current, and watts represent power. While these are all relevant concepts in electrical theory, they do not define impedance. Hence, ohms is the appropriate unit specifically for impedance, as it quantifies how much a component resists the flow of electric current in an AC circuit.