Electrical circuit.
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Series and Parallel circuit.
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Single wire, two wire and three wire system.
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Simple calculations of current, voltage and resistance.
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Testing of circuit.
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Navigation light circuit.
Electrical İnstruments.
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Ammeter
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Voltmeter
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Meggar
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Circuit breaker. its principal and construction details.
Electrical Units.
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Fair knowledge of electrical units.
- Electrical Basic.
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Residual magnetism.
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Line of forces.
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İnduction.
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E.M.F
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Ohm's law.
Electrical Machines.
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Principal and working of AC DC generators and Motors.
Electrical switchboard.
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Knowledge of operations.
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Maintenance of instruments.
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Maintenance of fitted device on main panel.
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Putting alternators/generators in parallel.
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Tracing earth fault.
Electrician Exam's Questions Answers Download
1. What is the difference
between series and parallel circuit? In a series circuit, the current
through each of the components is the same, and the voltage across the circuit
is the sum of the voltages across each component. In a parallel circuit, the
voltage across each of the components is the same, and the total current is the
sum of the currents through each component.
2. How to trace out fault in
an electrical circuit?
Step
1 - Power Down
To trace a short circuit, all
the electrical switches should be turned off. All lights and other electric
appliances should be unplugged. The tripped circuit breaker should be reset. A
replacement should be completed if there is a fuse instead of a circuit
breaker.
Step
2 - Check Receptacles or Switches
After resetting the breaker, if
it trips again immediately, there is a possibility of a short circuit in a
receptacle or a switch.
Step
3 - Narrow it Down
If the circuit breaker does not
trip, turn on each switch one at a time until the breaker trips again. When the
breaker trips upon turning on a particular switch, it is evident that there is
a short circuit in a fixture or receptacle controlled by the switch.
Step
4 - Identify a Particular Electrical Appliance
When the circuit breaker does
not trip even after turning all the switches on, then you can conclude that the
original problem started with an electrical appliance somewhere inside the
home. Return to the electrical appliances and lights and begin plugging them in
one by one. As soon as the breaker trips, whichever appliance is plugged in at
that moment can be identified as problematic and isolated. The issue could lie
in the plug, the cord, or the appliance itself.
3. How circuit breaker work?
A circuit breaker is an automatically
operated electrical switch designed to protect an electrical circuit from
damage caused by excess current from an overload or short circuit. Its basic
function is to interrupt current flow after a fault is detected. Unlike a fuse,
which operates once and then must be replaced, a circuit breaker can be reset
(either manually or automatically) to resume normal operation.
4. How fire alarm work and
how to check it?
·
Inspect the smoke
alarm visually to ensure that dust and debris aren’t blocking the air entry
points, and that there’s no damage.
·
Hold and press
the button on the smoke alarm, which should release a loud siren. If you do not
hear the alarm, or the alarm sound is quiet, you may need to replace the
batteries. If the alarm still doesn’t work after a battery replacement,
exchange the entire unit.
·
It may be a good
idea to ask a family member to walk around the home while you’re testing the
alarm to ensure that it can be heard from every point in the property. The same
technique can apply to business premises.
·
Make sure that
the smoke alarm is working by presenting it with actual smoke. Though the
button can test whether the batteries are working, placing 2 or 3 lighted
matches underneath the unit can ascertain whether it’s performing its primary
function.
5. What Navigation light is?
And describe the working principle of navigation light?
A navigation light, also known
as a running or position light, is a source of illumination on a vessel,
aircraft or spacecraft. Navigation lights give information on a craft's
position, heading, and status. Their placement is mandated by international conventions
or civil authorities. Navigation lights are not intended to provide
illumination for the craft making the passage, only for other craft to be aware
of it.
Operational
guidance for ships navigational light circuit
The supply to the navigation lights
circuit must be maintained under all circumstances and special provisions are
therefore made. To avoid any possibility of accidental open circuits the
distribution board for the navigation lights supplies no other circuit. A
changeover switch provides an alternative source of supply should the main
supply fail. If the navigation lights fail, a visual or audible indication must
be given.
A navigation lights circuit is shown in Figure. Two sources
of supply are available from the changeover switch. A double pole switch
connects the supply to each light circuit, with a fuse in each line, A relay in
the circuit will operate the buzzer if an open circuit occurs, since the relay
will de-energies and the trip bar will complete the buzzer circuit. A resistance
in series with the indicating lamp will ensure the navigation lights operate
even if the indicating lamp fails.
A main supply failure will result in all the indicating
lamps extinguishing but the buzzer will not sound. The changeover switch will
then have to be moved to the alternative supply.
6. How many types of
navigation lights in the ship?
Navigation lights help you and other boaters determine which
is the give-way vessel when encountering each other at night. These lights must
be displayed from sunset to sunrise and during periods of restricted
visibility, such as fog. There are four common navigation lights.
Sidelights:
These red and green lights are called
sidelights (also called combination lights) because they are visible to another
vessel approaching from the side or head-on. The red light indicates a vessel's
port (left) side; the green indicates a vessel's starboard (right) side.
Sternlight:
This white light is seen only from
behind or nearly behind the vessel.
Masthead
Light: This white light shines
forward and to both sides and is required on all power-driven vessels. (On
power-driven vessels less than 39.4 feet in length, the masthead light and
sternlight may be combined into an all-round white light; power-driven vessels
39.4 feet in length or longer must have a separate masthead light.) A masthead
light must be displayed by all vessels when under engine power. The absence of
this light indicates a sailing vessel because sailboats under sail display only
sidelights and a sternlight.
All-Round
White Light: On power-driven vessels
less than 39.4 feet in length, this light may be used to combine a masthead
light and sternlight into a single white light that can be seen by other
vessels from any direction. This light serves as an anchor light when
sidelights are extinguished.
7. How to turn emergency
generator on load?
Procedure
for Battery Start
a.
Go to the emergency generator room and find the panel for emergency generator.
b.
Put the switch on the test mode from automatic mode. The generator will start
automatically but will not come on load.
c.
Check voltage and frequency in the meter.
d.
Keep the generator running for 10-15 min and check the exhaust temp and other
parameters.
e.
Check the sump level.
f. For stopping the generator,
put the switch in manual and then stop the generator.
Procedure
for Hydraulic Start
g.
Out the switch in manual mode as stated above and check the pressure gauge for
sufficient oil pressure.
h.
Open the valve from accumulator to generator.
i.
Push the spring loaded valve and the generator should start.
j.
Check voltage and frequency.
k.
Keep the generator running for 10-15 min and check the exhaust temp and other
parameters.
l.
Check the sump level
m.
For stopping, use the manual stop button from the panel.
n. After stopping the
generator, pressurize the hydraulic accumulator to desired pressure.
o. Close the valve from
accumulator to generator.
Procedure
for Automatic Start
p.
For automatic start, we know that there is a breaker which connects Emergency
Switch Board (ESB) and Main Switch Board (MSB); and there is also an interlock
provided due to which the emergency generator and Main power of the ship cannot
be supplied together.
q.
Therefore, we simulate by opening the breaker from the tie line, which can be
done from the MSB or the ESB panel.
r.
After opening the breaker, the emergency generator starts automatically with
the help of batteries and will supply essential power to machinery and pumps
connected to ESB.
s.
For stopping the generator, the breaker is closed again and due to the
interlock the generator becomes off load.
t.
Now again put the switch to manual mode to stop the generator.
u. Press stop and the generator
will stop.
8. What does synchronization
means?
In an alternating current
electric power system, synchronization is the process of matching the speed and
frequency of a generator or other source to a running network. An AC generator
cannot deliver power to an electrical grid unless it is running at the same
frequency as the network. If two segments of a grid are disconnected, they
cannot exchange AC power again until they are brought back into exact
synchronization.
9.
What is current, voltage and resistance?
Voltage is the difference in charge between
two points.
Current is the rate at which charge is
flowing.
Resistance
is a
material’s tendency to resist the flow of charge (current).
10. What is power factor and
what does its importance?
Power Factor is very important
for every power system or company, because it helps in maintaining inductive
load. As its values lies in between 0–1.
Any system which has a power factor close to 1 is considered
as good or excelent system, whereas any system which has a power factor close
to 0 (Like 0.2, 0.3, 0.4, 0.5, 0.6) is considered as bad system and that power
company have to pay something as a penalty fee. Because whenever power factor is not
good or lagging power factor then imposes a severe impact on power suppling
side.
You can see in above formula
that when P.F is low then Apparent power or total power increases, it means
Power supplying company has to provide more power to that company which has low
P.F & this increases the line current which has a bad impact on the
conductors or cables through which power is flowing, conductors becomes hot and
heat dissipation will high, which causes a power supplying company to produce
more power in order to compensate the power demand, their production cost of
power will be increase and equipment cost also increases. So it is better to
have a good P.F, in order to avoid penalty and other things.
11. What is fire and its
types?
This is The Fire Triangle.
Actually, it's a tetrahedron, because there are four elements that must be
present for a fire to exist. There must be oxygen to sustain combustion, heat
to raise the material to its ignition temperature, fuel to support the
combustion and a chemical reaction between the other three elements. Remove any
one of the four elements to extinguish the fire. The concept of Fire Protection
is based upon keeping these four elements separate.
Types of Fires
Not all fires are the same. Per
NFPA 10, burning may be classified into one or more of the following fire
classes and your fire protection specialist will select the right fire
extinguisher size and agent for the hazard.
1.
Class A
fires are fires in ordinary combustibles such as wood, paper, cloth, rubber,
and many plastics.
2.
Class B fires
are fires in flammable liquids such as gasoline, petroleum greases, tars, oils,
oil-based paints, solvents, alcohols. Class B fires also include flammable
gases such as propane and butane. Class B fires do not include fires involving
cooking oils and grease.
3.
Class C
fires are fires involving energized electrical equipment such as computers,
servers, motors, transformers, and appliances. Remove the power and the Class C
fire becomes one of the other classes of fire.
4. Class D fires are fires in combustible metals such as magnesium,
titanium, zirconium, sodium, lithium, and potassium.
5.
Class K fires
are fires in cooking oils and greases such as animal and vegetable fats.
Some
types of fire extinguishing agents can be used on more than one class of fire.
Others have warnings where it would be dangerous for the operator to use on a
particular fire extinguishing agent.
12. How to test smoke detector?
Press
and hold the test button on the smoke detector. It can take a few seconds to
begin, but a loud, ear-piercing siren should emanate from the smoke detector
while the button is pressed. If the sound is weak or nonexistent, replace your
batteries. If it has been more than six months since you last replaced the
batteries (whether your detector is battery-powered or hardwired), change them
now regardless of the test result, and test the new batteries one final time to
help ensure proper functioning. You should also look at your smoke detector to
make sure there’s no dust or other substance blocking its grates, which may
prevent it from working even if the batteries are new.
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