T0A-2010: AC power circuits; hazardous voltages, fuses and circuit breakers, grounding, lightning protection, battery safety, electrical code compliance
T0A01:
Which is a commonly accepted value for the lowest voltage that can cause a dangerous electric shock?
30 volts
12 volts
120 volts
300 volts
T0A02:
How does current flowing through the body cause a health hazard?
All of these choices are correct
By heating tissue
It disrupts the electrical functions of cells
It causes involuntary muscle contractions
T0A03:
What is connected to the green wire in a three-wire electrical AC plug?
Safety ground
Neutral
Hot
The white wire
T0A04:
What is the purpose of a fuse in an electrical circuit?
To interrupt power in case of overload
To prevent power supply ripple from damaging a circuit
To limit current to prevent shocks
All of these choices are correct
T0A05:
Why is it unwise to install a 20-ampere fuse in the place of a 5-ampere fuse?
Excessive current could cause a fire
The larger fuse would be likely to blow because it is rated for higher current
The power supply ripple would greatly increase
All of these choices are correct
T0A06:
What is a good way to guard against electrical shock at your station?
All of these choices are correct
Use three-wire cords and plugs for all AC powered equipment
Connect all AC powered station equipment to a common safety ground
Use a circuit protected by a ground-fault interrupter
T0A07:
Which of these precautions should be taken when installing devices for lightning protection in a coaxial cable feedline?
Ground all of the protectors to a common plate which is in turn connected to an external ground
Include a parallel bypass switch for each protector so that it can be switched out of the circuit when running high power
Include a series switch in the ground line of each protector to prevent RF overload from inadvertently damaging the protector
Keep the ground wires from each protector separate and connected to station ground
T0A08:
What is one way to recharge a 12-volt lead-acid station battery if the commercial power is out?
Connect the battery to a car’s battery and run the engine
Cool the battery in ice for several hours
Add acid to the battery
All of these choices are correct
T0A09:
What kind of hazard is presented by a conventional 12-volt storage battery?
Explosive gas can collect if not properly vented
It emits ozone which can be harmful to the atmosphere
Shock hazard due to high voltage
All of these choices are correct
T0A10:
What can happen if a lead-acid storage battery is charged or discharged too quickly?
The battery could overheat and give off flammable gas or explode
The voltage can become reversed
The memory effect will reduce the capacity of the battery
All of these choices are correct
T0A11:
Which of the following is good practice when installing ground wires on a tower for lightning protection?
Ensure that connections are short and direct
Put a loop in the ground connection to prevent water damage to the ground system
Make sure that all bends in the ground wires are clean, right angle bends
All of these choices are correct
T0A12:
What kind of hazard might exist in a power supply when it is turned off and disconnected?
You might receive an electric shock from stored charge in large capacitors
Static electricity could damage the grounding system
Circulating currents inside the transformer might cause damage
The fuse might blow if you remove the cover
T0A13:
What safety equipment should always be included in home-built equipment that is powered from 120V AC power circuits?
A fuse or circuit breaker in series with the AC "hot" conductor
An AC voltmeter across the incoming power source
An inductor in series with the AC power source
A capacitor across the AC power source
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