Deep Dive: T5A04
The correct answer is C: Ohms. The units of electrical resistance are ohms (symbol: Ω). Resistance is the opposition to current flow in a circuit, and the ohm is the standard unit for measuring this opposition. One ohm is defined as the resistance that allows one ampere of current to flow when one volt is applied. Resistance is a fundamental property of materials - conductors have low resistance (allow current to flow easily), while insulators have very high resistance (oppose current flow). Understanding resistance is crucial for amateur radio, as it affects power delivery, signal loss in feedlines, and antenna matching.
Why Other Answers Are Wrong
Option A: Incorrect. Siemens is the unit of conductance (the inverse of resistance), not resistance itself. Option B: Incorrect. Mhos is an older term for Siemens (conductance), not the unit of resistance. Option D: Incorrect. Coulombs measure electric charge, not resistance.
Exam Tip
Resistance = Ohms. Remember: Electrical resistance is measured in ohms (Ω). Resistance opposes current flow.
Memory Aid
**R**esistance = **O**hms (think 'R = O' = Resistance = Ohms, symbol Ω)
Real-World Example
Your antenna feedline has a resistance of 0.1 ohms. This low resistance means the feedline doesn't significantly oppose current flow, so most of your transmitter's power reaches the antenna. If the feedline had high resistance (many ohms), it would waste power as heat and reduce the power delivered to your antenna.
Source & Coverage
Question Pool: 2022-2026 Question Pool
Subelement: T5A
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 T5A topic.