Ham Radio General Class Practice Test

What is impedance in an electrical circuit?

1. The electric charge stored by a capacitor

2. The inverse of resistance

3. The opposition to the flow of current in an AC circuit

4. The force of repulsion between two similar electric fields

The correct answer is: The opposition to the flow of current in an AC circuit

Impedance is defined as the opposition to the flow of alternating current (AC) in an electrical circuit. It encompasses both resistance and reactance, which come into play due to the presence of inductors and capacitors in the circuit. While resistance opposes the flow of direct current (DC), reactance varies with the frequency of the AC signal, providing a more complex form of opposition. In AC circuits, impedance is a critical concept because it determines how effectively power is transferred and how circuits behave under various frequencies. This characteristic is represented in complex form, involving both magnitude (measured in ohms) and phase (which reflects the time shift between voltage and current). Therefore, option C accurately captures the essence of impedance as it pertains to AC circuits. The other choices do not accurately describe impedance: the electric charge stored by a capacitor relates to capacitance, the inverse of resistance refers to conductance, and the force of repulsion between similar electric fields is a concept related to electric fields rather than impedance.