3.6 KiB
T0A – Power circuits and hazards: hazardous voltages, fuses and circuit breakers, grounding, electrical code compliance; Lightning protection; Battery safety
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T0A01 (B) Which of the following is a safety hazard of a 12-volt storage battery? #card
- A. Touching both terminals with the hands can cause electrical shock
- B. Shorting the terminals can cause burns, fire, or an explosion
- C. RF emissions from a nearby transmitter can cause the electrolyte to emit poison gas
- D. All these choices are correct
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T0A02 (D) What health hazard is presented by electrical current flowing through the body? #card
- A. It may cause injury by heating tissue
- B. It may disrupt the electrical functions of cells
- C. It may cause involuntary muscle contractions
- D. All these choices are correct
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T0A03 (B) In the United States, what circuit does black wire insulation indicate in a three-wire 120 V cable? #card
- A. Neutral
- B. Hot
- C. Equipment ground
- D. Black insulation is never used
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T0A04 (B) What is the purpose of a fuse in an electrical circuit? #card
- A. To prevent power supply ripple from damaging a component
- B. To remove power in case of overload
- C. To limit current to prevent shocks
- D. All these choices are correct
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T0A05 (C) Why should a 5-ampere fuse never be replaced with a 20-ampere fuse? #card
- A. The larger fuse would be likely to blow because it is rated for higher current
- B. The power supply ripple would greatly increase
- C. Excessive current could cause a fire
- D. All these choices are correct
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T0A06 (D) What is a good way to guard against electrical shock at your station? #card
- A. Use three-wire cords and plugs for all AC powered equipment
- B. Connect all AC powered station equipment to a common safety ground
- C. Install mechanical interlocks in high-voltage circuits
- D. All these choices are correct
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T0A07 (D) Where should a lightning arrester be installed in a coaxial feed line? #card
- A. At the output connector of a transceiver
- B. At the antenna feed point
- C. At the ac power service panel
- D. On a grounded panel near where feed lines enter the building
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T0A08 (A) Where should a fuse or circuit breaker be installed in a 120V AC power circuit? #card
- A. In series with the hot conductor only
- B. In series with the hot and neutral conductors
- C. In parallel with the hot conductor only
- D. In parallel with the hot and neutral conductors
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T0A09 (C) What should be done to all external ground rods or earth connections? #card
- A. Waterproof them with silicone caulk or electrical tape
- B. Keep them as far apart as possible
- C. Bond them together with heavy wire or conductive strap
- D. Tune them for resonance on the lowest frequency of operation
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T0A10 (A) What hazard is caused by charging or discharging a battery too quickly? #card
- A. Overheating or out-gassing
- B. Excess output ripple
- C. Half-wave rectification
- D. Inverse memory effect
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T0A11 (D) What hazard exists in a power supply immediately after turning it off? #card
- A. Circulating currents in the dc filter
- B. Leakage flux in the power transformer
- C. Voltage transients from kickback diodes
- D. Charge stored in filter capacitors
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T0A12 (B) Which of the following precautions should be taken when measuring high voltages with a voltmeter? #card
- A. Ensure that the voltmeter has very low impedance
- B. Ensure that the voltmeter and leads are rated for use at the voltages to be measured
- C. Ensure that the circuit is grounded through the voltmeter
- D. Ensure that the voltmeter is set to the correct frequency