Practical takeaway
Hazardous voltages, fuses/breakers, grounding, electrical-code practice, lightning protection, and battery safety.
T0A · 12 pool questions
Electrical, Lightning & Battery Safety
Hazardous voltages, fuses/breakers, grounding, electrical-code practice, lightning protection, and battery safety.
Technician exam focus
This group contains 12 questions in the current pool. The teaching below keeps the important tested terms visible while explaining what they mean in normal Amateur Radio use.
1. Low voltage can still deliver huge current
A 12-volt storage battery normally will not shock you through dry skin, but shorting its terminals can cause burns, fire, or an explosion. Rapidly charging or discharging an unprotected battery can cause overheating or out-gassing.
2. Current through the body can injure several ways
Electrical current can heat tissue, disrupt the body’s own electrical functions, and cause involuntary muscle contractions. Treat exposed mains voltage and high-voltage DC as hazardous even when the current source seems small.
3. Protect the hot conductor
In a U.S. three-wire 120 V AC cable, black is hot, white is neutral, and green/bare is equipment ground. A fuse or circuit breaker belongs in series with the hot conductor so opening it removes dangerous voltage from the protected equipment.
4. Grounding and lightning protection are a system
Install a coax lightning arrester on a grounded panel near where feed lines enter the building. Bond external ground rods/earth connections together with heavy wire or conductive strap. Separate unbonded grounds can develop dangerous voltage differences during a fault or lightning event.
5. Stored charge can remain after power is off
High-voltage filter capacitors can retain a dangerous charge after equipment is switched off. Discharge them safely before working inside equipment, and use meters/leads rated for the voltage you are measuring.
T0A checklist
- Battery terminal short: burns, fire, or explosion.
- Rapid charge/discharge of an unprotected battery: overheating or out-gassing.
- 120 V AC: black = hot; white = neutral; green/bare = safety ground.
- Fuse/breaker: series with the hot conductor.
- Lightning arrester: grounded panel near the feed-line entry.
- Bond all external ground rods with heavy wire or conductive strap.
- Power-supply capacitors can retain dangerous charge after power is off.
Exam scope: NCVEC 2026–2030 Technician Class (Element 2), effective July 1, 2026 through June 30, 2030, with February 19, 2026 errata. The current NCVEC pool is the exam authority; explanatory prose here is SPARKA teaching material. NCVEC pool