Technician T0A: Electrical safety
These are the 12 official questions in group T0A of the 2026–2030 Technician question pool, with the correct answer marked and a plain-English explanation of why it's right. The real exam asks one question from this group.
- T0A01Question 1
Which of the following is a safety hazard of a 12-volt storage battery that lacks internal protection circuitry?
- ATouching both terminals with your hands can cause electrical shock
- BShorting the terminals can cause burns, fire, or an explosion Correct
- CRF emissions from a nearby transmitter can cause the electrolyte to emit poison gas
- DAll these choices are correct
Why: A shorted battery can deliver huge current, causing burns, fire or an explosion.
- T0A02Question 2
What health hazard is posed by electrical current flowing through the body?
- AIt may cause injury by heating body tissue
- BIt may disrupt the electrical functions of cells
- CIt may cause involuntary muscle contractions
- DAll these choices are correct Correct
Why: Current through the body can cause heating, muscle contractions and fibrillation. All the choices are correct.
- T0A03Question 3
In the United States, what circuit does black wire insulation indicate in a three-wire 120 V AC cable?
- ANeutral
- BHot Correct
- CEquipment ground
- DNegative
Why: Black insulation is the hot wire in US 120 V wiring.
- T0A04Question 4
What is the purpose of a fuse in an electrical circuit?
- ATo prevent power supply ripple from damaging a component
- BTo remove power in case of an overload Correct
- CTo limit current and prevent shocks
- DAll these choices are correct
Why: A fuse removes power when there's an overload.
- T0A05Question 5
Why should a 5-ampere fuse never be replaced with a 20-ampere fuse?
- AThe larger fuse would be likely to blow because it is rated for higher current
- BThe power supply ripple would greatly increase
- CExcessive current could cause a fire Correct
- DVoltage drop in the higher current fuse could result in excessively low voltage to the device
Why: A bigger fuse lets too much current flow before it blows, which could cause a fire.
- T0A06Question 6
What is a good way to guard against electrical shock at your station?
- AUse three-wire cords and plugs for all AC powered equipment
- BConnect all AC powered station equipment to a common safety ground
- CEnsure all capacitors used for high-voltage DC are fully discharged before working inside equipment
- DAll these choices are correct Correct
Why: Grounding, three-wire cords and GFCIs all protect against shock. All the choices are correct.
- T0A07Question 7
Where should a lightning arrester be installed in a coaxial feed line?
- AAt the output connector of a transceiver
- BAt the antenna feed point
- CAt the AC power service panel
- DOn a grounded panel near where feed lines enter the building Correct
Why: Put the lightning arrester on a grounded panel near where the feed lines enter the building.
- T0A08Question 8
Where should a fuse or circuit breaker be installed in a 120V AC power circuit?
- AIn series with the hot conductor only Correct
- BIn series with the hot and neutral conductors
- CIn parallel with the hot conductor only
- DIn parallel with the hot and neutral conductors
Why: A fuse or breaker goes in series with the hot conductor only.
- T0A09Question 9
What should be done to all external ground rods or earth connections?
- AWaterproof them with silicone caulk or electrical tape
- BKeep them as far apart as possible
- CBond them together with heavy wire or conductive strap Correct
- DTune them for resonance on the lowest frequency of operation
Why: Bond all external ground rods together with heavy wire or strap.
- T0A10Question 10
What hazard exists when rapidly charging or discharging an unprotected battery?
- AOverheating or out-gassing Correct
- BExcess output ripple
- CElectric shock
- DOvervoltage
Why: Rapid charging or discharging can overheat a battery or make it out-gas.
- T0A11Question 11
What hazard exists in a power supply immediately after turning it off?
- ACirculating currents in the dc filter
- BLeakage flux in the power transformer
- CVoltage transients from kickback diodes
- DCharge stored in filter capacitors Correct
Why: Filter capacitors can hold a dangerous charge after the supply is turned off.
- T0A12Question 12
Which of the following precautions should be taken when measuring high voltages with a voltmeter?
- AEnsure that the voltmeter has very low impedance
- BEnsure that the voltmeter and its leads are rated for use at the voltages being measured Correct
- CEnsure that the circuit is grounded through the voltmeter
- DEnsure that the voltmeter is set to the correct frequency
Why: Make sure the voltmeter and its leads are rated for the voltage you're measuring.