4-4-14
Electricity travels at ? . a.56,000 mi/s b.95,000 mi/s c.186,000 mi/s d.300,000 mi/s
186,000 mi/s
If a 7,200-240/480-volt transformer has 120 volts introduced into X1, the voltage available at H1 would be ? . a.180 b.1,800 c.2,400 d.4,160
B. 1,800
When grounds are applied for protection on a line that is being back-fed from a generator, the generator will usually ? . a.be limited in its output b.keep running c.short out within 1 minute d.trip out within 5 minutes
B. Keep running
One reason to take appropriate voltage checks at a meter base that has been disconnected for nonpayment is because ? . a.a dead short from the lower to upper jaws may exist b.all four socket jaws are energized c.the socket is back-fed d.all the above
D. All the above
The high voltage potential of a back-fed transformer is limited by the value of the input ? and transformer ratio. a.current b.frequency c.impedance d.voltage
D. Voltage
A conductor that is broken and laying on the ground is safe from back-feed as long as contact with the earth is maintained. Select one: True False
False
A distribution transformer's rated primary voltage will always be present at the primary bushings regardless of how much voltage is introduced into the secondary. Select one: True False
False
If the primary is being fed through a transformer during a back-feed situation, the primary will always be at nominal voltage. Select one: True False
False
It is safe to cut a neutral that ties two feeder lines together because any neutral current will flow only through the earth. Select one: True False
False
Working out of a man lift will guarantee that a Qualified Electrical Worker cannot get in series with a broken neutral. Select one: True False
False
If a network transformer is disconnected from the primary, back-feed can still be a problem. Select one: True False
True
If an energized service to a house has the neutral broken from rubbing on a tree, a serious shock might result if a worker's bare hands bridge the open point. Select one: True False
True
The best way to assure a transformer is not being back-fed is to remove its secondary leads after disconnecting it from the primary. Select one: True False
True
It takes as little as ? AC to produce ? , which will cause the heart to go into fibrillation. a.50 V / 25 mA b.50 V / 50 mA c.75 V / 75 mA d.100 V / 50 mA
b.50 V / 50 mA
In case of an electrical shock, heart fibrillation requires ? . a.a 120 V shock across the chest b.advanced medical attention c.intermediate CPR d.no action because it is a temporary condition
b.advanced medical attention
Generators used in hospitals are normally equipped with ? and usually pose no hazard for Qualified Electrical Workers, because they cannot back-feed into the distribution system. a.automatic dispatcher notification b.automatic double throw switches c.lights that flash when it is operating d.warning sirens
b.automatic double throw switches
When removing and replacing transformers, disconnecting the transformer from its ? must be done first. After the transformer is changed out, connect the ? leads last to isolate the transformer in case there is back-feed from the secondary side. a.ground / secondary low voltage source b.primary source / primary c.primary source / secondary low voltage source d.secondary low voltage source / primary
c.primary source / secondary low voltage source
To avoid becoming a victim of back-feed, ? when making repairs to lines or equipment during a storm outage. a.use live-line tools b.wear a flame retardant shirt c.wear rubber gloves d.wear rubber overshoes
c.wear rubber gloves
The high voltage winding of a transformer will be energized by ? when the low voltage winding is back-fed from a customer load. a.capacitive reactance b.equipotenial grounding c.impedance d.mutual induction
d.mutual induction
