Deep Dive: T5C05
The correct answer is D: The ohm. The unit of impedance is the ohm (symbol: Ω), the same unit used for resistance. Impedance is the total opposition to AC current flow, which includes both resistance and reactance (from capacitance and inductance). Impedance is measured in ohms because it represents opposition to current flow, just like resistance. However, impedance is more complex than resistance - it includes both resistive and reactive components. At DC, impedance equals resistance. At AC, impedance includes the effects of capacitance and inductance (reactance). The ohm is used for both resistance and impedance because they're both measures of opposition to current flow.
Why Other Answers Are Wrong
Option A: Incorrect. The volt is the unit of voltage, not impedance. Voltage and impedance are different quantities. Option B: Incorrect. The ampere is the unit of current, not impedance. Current and impedance are different quantities. Option C: Incorrect. The coulomb is the unit of electric charge, not impedance. Charge and impedance are different quantities.
Exam Tip
Impedance unit = Ohms. Remember: Impedance is measured in ohms (Ω), the same unit as resistance. Impedance is the total opposition to AC current flow.
Memory Aid
**I**mpedance = **O**hms (think 'I = O' = Impedance = Ohms, same as resistance)
Real-World Example
Your antenna might have an impedance of 50 ohms. This means it presents 50 ohms of opposition to AC current flow at the operating frequency. The impedance includes both resistance and reactance. Understanding that impedance is measured in ohms helps you understand antenna matching and feedline specifications.
Source & Coverage
Question Pool: 2022-2026 Question Pool
Subelement: T5C
Reference: FCC Part 97.3
Key Concepts
Verified Content
Question from the official FCC Technician Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the T5C topic.