Electrical Objective Questions part 1



1. A certain appliance uses 700 W. If it is allowed to run continuously for 36 days, how many kilowatt-hours of energy does it consume(up to 1 deci)

                         ANS:-   700*36*24/1000=604.8

 2. Alfa particles enter an electromagnetic field where the electric intensity is 300v/m and the magnetic  induction is 0.200T what is the velocity of Alfa particles

              F=qvB                   V=F/qB=300/2*.2=750                   charge of an alfa particle is 2

3. What is the magnetomotive force ina 75 turn coil of wire when ther are 4A of current through it?

                  F=NI=75*4=300Ampere turn AT



 4. Resistances of 20,15,25 ohm are connected in series across a 36 v line.calculate voltage drop across 25 ohm resistance

           R=20+15+25=60   V/R=I=36/60=0.6     V=RI=.6*25=15

5. Two pole motor running at 4800 rpm calculate frequency

            N=120f/p       F=NP/120=4800*2/120=80

 6. A poly phase motor driving an engine room pump fails to start, when trying to identify the cause of failure, which of the following steps are applicable.(multiple ans)
A. visually examine the motor for open circuit fault
B. visually examine the stator for open circuit fault
C. Reverse the direction of current for its working
D. Perform the infinite resistance test


7.If an intrinsic semiconductor is doped with a very small amount of boron then the extrinsic semiconductor set formed, the no. of electrons and holes will
A.both Dec.
B.increase and decrease
C.Both increase
D.Decrease and increase


8.In what range of voltages is the transistor in the linear region of its operation?
A.0 < VCE < 0.7 V
B.0.7 < VCE < 1.4 V
C.0.7 < VCE < VCE(max)
D.0 < VCE < VCE(max)


9.The current in a semiconductor is produced by:
A. Electrons
B. Neutrons
C. Protons
D. Holes


10.Brushless generators are designed to operate without the use of
A.brushes
B. sliprings
C. commutators
D. all of the above


11.Where a thermal-acting breaker is required to be used in an area of unusually high, low, or constantly
fluctuating temperatures, an ambient compensating element must be used. This element consists of a
A. Cylindrical spring on the contact arm.
B. Conical spring on the contact arm.
C. Second bimetal element.
D. Second electromagnet.


12.A fuse that blows often should be replaced only with a fuse of
A. the recommended current and voltage rating
B. higher current and voltage rating
C. higher current and lower voltage rating
D. lower current and higher voltage rating


13.Which of the listed precautions should be taken when cleaning the internals of a motor with compressed
air?
A. Open the machine on both ends so as to allow the air and dust to escape.
B. Be certain that the circuit breaker is opened and tagged on the feeder panel.
C. Be certain that the air is clean and as dry as possible.
D. Ensure that the fuse in the motor is removed.


14.Fuses placed in series with a thermal trip = - type circuit breaker are used for
A. Time-delay protection
B. Short-circuit protection
C. Short duration surge protection
D. Sustained overload protection


15.A molded-case breaker provides protection against short-circuits by usinga/an
A. Shading coil.
B. Arc quencher.
c.Electromagnet.
D.Holding coil.


16.The induced voltage across a stationary conductor in a steady magnetic field is zero.
A.True
B.False


17.When paralleling an AC generator with live bus bars, which of the following precautions are applicable? ^
A. Generator firequency should be slightly lower than bus bar frequency
B. Generator frequency should be slightly higher than bus bar frequency
C. Generator voltage should be in phase with bus bar voltage
D. Generator voUage should be out of phase with bus bar voltage ""^


18.Tightly knit metal braid wire can be used with a printed circuit board when
A. Conductor flexibility is required
B. De-soldering components in the circuit
C. Electrically produced magnetic fluxes would cause inaccuracies in adjacent components
D. Reactance in the circuit must be kept to a minimum


19.A poly-phase motor driving an engine room pump fails to start. When trying to identify the cause of
failure, which of the following steps are applicable?
A. Visually examine motor for open circuit faults.
B. Visually examine starter for open circuit faults.
C. Reverse the direction of electrical supply to check if it works.
D. Perform the infinite resistance test.


20.AC circuits possess characteristics of resistance, inductance, and capacitance.The capacitive reactance of
acircuit is expressed in
A. ohms
B. mhos
C. hemys
D. farads



21.Altemating ciirrent circuits develop resistance, inductance and capacitance. The inductance of a coil is
expressed in .
A. ohms
B. mhos
C. henrys
D. farads


22.The basic measuring unit of inductance is the
A. coulomb 
B. ohm
C. farad 
D. henry



23. The greatest detrimental effect on idle electrical equipment, such as cargo pump motors,is the

A. Loss of residualmagnetism.

B. Absorption of moisture in the insulation.

C. Insulation vamish flaking.

D. Dirt collecting on the windings. ^



24.1f it takes 35 J of energy to move a charge of 6 C from one point to another, what is the voltage between the two points? Your answer should be correct to two decimals.

V=E/Q=35/6=5.83V

25.Which of the following statements is true concerning a poly-phase synchronous propulsion motor? 
A. The motor is started as an induction motor.
B. Resistance is gradually added to the rotor circuit. 
C. The starting current is held below the rated current.
D. The field winding is energized for starting purposes only.


26.When reading electrical motor controller diagrams, it helps to know that .
A. current paths in the control circuit are drawn as heavy lines and in the power circuit as lighter lines
B. current paths in the power circuit are drawn as heavy lines and in control circuit as lighter lines
C. circuits subject to 500 volts or greater are drawn as heavy lines and below 500 volts as lighter lines
D. circuits subject to 500 volts or greater are drawn as light lines and below 500 volts as heavy



27. Large cable sizes are formed as individual conductors that may be comprised of several smaller strands 
to .

A. obtain the flexibility required for easy handling

B. reduce the overall weight of the wire nm

C. reduce the number of supports needed for a horizontal overhead run

D. all of the above




28.Which of the following is having Di-Electric Constant 80?

A. Air

B. water

C. Mica

D. Caster oil  



29.Where a thermal-acting breaker is required to be used in an area of unusually high, low, or constantly

fluctuating temperatmes, an ambient compensating element must be used. This element consists of a

A. cylindrical spring on the contact arm

B. conical spring on the contact arm

C. second bimetal element

D. second electromagnet




30. A semiconductor that decreases in resistance with an increase in temperature is known as a

A. resistor

B. thermistor

C. diode

D. thermopile




31. In a diesel electric plant, raising the generator's field excitation will cause the DC propulsion motor to

A increase in speed

B decrease in speed

e affect generator speed only

D affect main motor speed if done in conjunction with higher generator engine speeds







32.Which of the following statements best describes the material known as varnished cambric?

(A) Felted asbestos sealed with varnish.

(B) Cotton cloth coated with insulating varnish. 

(C) Rubber insulation coated with a layer of tin.

(D) Paper impregnated with mineral oil, specially wrapped with nonmetallic tape, and coated with varnish. 




33.The part of a fuse that melts and opens the circuit is made of .

(A) Copper and antimony

(B) Steel and Babbitt

(C) Aluminum or beryllium alloy 

(D) Zinc or an alloy of tin and lead




34.A synchronous motor maintains synchronism with the rotating field because .

(A) field strength varies directly with rotors Up

(B) DC current applied to the rotor coils causes the rotor magnets to lock in with the rotating flux of the stator

(C) the stator poles are dragged around due to the flux created by the excitation current

(D) the stator flux rotates in the opposite direction 




35. Silicon diodes designed for a specific reverse breakdown voltage, become useful as an electronic power 
supply voltage regulator, called.............

(A) tunnel diodes

(B) hot-carrier diodes

(C) compensating diodes

(D) Zener diodes



36.Time delayed or delayed action-type fuses are designed to .
(A) prevent grounds in branch circuits
(B) prevent opens in motor circuits
(C) permit momentary overloads without melting
(D) guard lighting and electronic circuits



37. PN DIODE ADVANTAGE OVER VACUUM DIODE ?

a) longer life

b) no warm up time

c) less delicate

d) all of the above




38.Electrons and protons of the same momentum enter normally into a uniform magnetic field of flux density B. mass of the electron is me (m suffix e) and mass of the proton is mp (m suffix p).if re (r suffix e) and rp (r suffix p) represents the radii of the path of the electrons and the protons respectively, calculate the ratio re/rp. your answer should be correct to 2 decimals..

ANS:- 

charged particle describe an anticlockwise circular path and magnetic force work as centripetal force. Thus 


F=qvB=mv2/r     qB=mv/r

     Here MpV and MeV are same because of same momentum

for electron qB=MeV/Re

for proton   qB=MpV/Rp


dividing bothe equation Re/Rp=1.00



39.The opposition to the magnetic lines of force in magnetic field is called

A. Resistance

B. Reluctance

C. Impedence

D. Inductance




40.Determine the order of doping in transistor (from high to low)

A. collector .base, emitter

B. Emitter,collector,base

C. Base, emitter,collector




41.A low voltage protection circuit is used in electric motor starting equipment to

A. Trip circuit contractor when the motor overspeed due to low voltage

B. Trip circuit contractor when the motor develops short circuit due to low voltage

C. Allows the motor to restart automatically on restoration of voltage without manual resetting

D. prevent motor from restarting automatically




42.Which of the following capacitor is having highest di electric constant 

A. air gap

B. glass 

C. paper

D. polyster



43.Which of the following conditions will occur when solenoid coil bums out of a cargo winch with a electrical brake.
A. The brake will be set by spring force. 
B. The motor will over speed and bums out
C. The load suspended by the cargo boom will fail 
D. Nothing will happen, the winch will continue to operate normally



44.Which of the following physical character does around rotor induction motor posses that squirrel cage 
motor does not

A. Slip rings

B. End rings 

C. A centrifugal clutch

D. End plates 




45. To prevent electric shock during electric arc welding 

A. Wear dry clothes

B. Wear insulated shoes

C. Keep first aid equipment ready

D. None of the above




46.Getting the value of a/c sign wave from ammeter and voltmeter is 

A. rms

B. Avg 

C. Peak




47.The appereant power in inductive circuit
a truepower
b lead
c inductive
d reactive




48.purpose of preferential trip to prevent

a. blackout

b. to avoid overload

c. to start heavy machinery

d, all




49.which of the capacity has dielectric constant of 1.0000

a. airgap

b. vaccum

c. water

d. electrolytes




50.When testing a capacitor with an analog type ohmmeter, a good capacitor will be indicated when

A there is no meter deflection

B the meter deflects to a low resistance value and remains there

C the meter deflects to a low resistance value and slowly increases towards infinity

D the meter deflects to a low resistance value and increases rapidly to a higher value, but stays fairly low




51.For a given line voltage, four heating coils will produce maximum heat when connected in
A. Parallel

B. series

C.same heat in both the time

D. none of the above




52.A semiconductor is damaged by a strong current, because of (1)------ (2)------ (3)-------

Ans: over load ,over current ,short circuit

53.what happens to the strength of electro magnetic field when current passing through an inductor is half__________-
a.1/4
b.1/2
c.2
d.4


54.Open-loop transfer function of a system having one zero with positive real values is called ------


      ANS:   phase function


55.The direction of induced EMF can be found with the help of -----

       ANS: Lenz's law


Plz post new questions in comment box..... we will update it and collect all the asked questions in one point.... or mail us on                 marinesite.blogspot@gmail.com








4 comments:

  1. question no 14 ans is b and not a
    refer uscg q 177

    ReplyDelete
    Replies
    1. corrections are always welcome..... plz post new question after your exam.... best wishes....

      Delete
  2. 1. *Open-loop transfer function of a system having one zero with positive real values is called nonminimum phase function is this correct?

    ReplyDelete
  3. Solve the equation for g(s)= (s^2 +3)/{(s^5)+(s^4)+(s^3)+(3s^2)+(2s)}?

    PS: From some closed loop system equation.

    ReplyDelete


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