Ham Amateur Radio Technician Practice Exam 2025 - Free Technician Practice Questions and Study Guide

Impedance is defined as the ratio of voltage to current in an alternating current (AC) circuit. This relationship reflects how much opposition a circuit presents to the flow of electric current. Impedance takes into account not just resistance, which opposes current flow and is measured in ohms, but also reactance, which arises from inductance and capacitance in the circuit.

In a circuit, impedance combines both the resistive and reactive components, making it a complex quantity expressed in ohms as well. The formula expressing this relationship can be formulated as \( Z = \frac{V}{I} \), where \( Z \) represents impedance, \( V \) is voltage, and \( I \) is current. This means that when voltage is applied across a circuit, impedance dictates how much current will flow as a result of that voltage, highlighting the crucial nature of impedance in AC analysis and design.

Understanding this definition aids in effectively grasping concepts related to circuit analysis, resonance, and the behavior of various components in a ham radio setup, which often utilizes AC signals.