FUNCTION -5 (ELECTRICAL)

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

ANS.: A

2. When reading electrical motor controller diagrams, it helps to know that _____
   1. current paths in the control circuit are drawn as heavy lines and in the power circuit as lighter lines
   2. current paths in the power circuit are drawn as heavy lines and in control circuit as lighter lines
   3. circuits subject to 500 volts or greater are drawn as heavy lines and below 500 volts as lighter lines
   4. circuits subject to 500volts or greater are drawn as light lines and below 500 volts as heavy

ANS.: B

3. Alternating current circuits develop resistance, inductance and capacitance. The inductance of a coil is expressed in
   1. Ohms
   2. Mhos
   3. Henrys
   4. farads

ANS.: C

4. Large cable sizes are formed as individual conductors that may be comprised of several smaller strands to
   1. obtain the flexibility required for easy handling
   2. reduce the overall weight of the wire run
   3. reduce the number of supports needed for a horizontal overhead run
   4. all of the above

ANS.: A

5. Which of the following is having Di-Electric Constant 80?
   1. Air
   2. Water
   3. Mica
   4. Castor oil

ANS.: B

6. 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
   1. cylindrical spring on the contact arm
   2. conical spring on the contact arm
   3. second bimetal element
   4. second electromagnet

ANS.: C

7. Which of the following precautions should you take when securing propulsion generators and motors for an extended period of time?
   1. Disconnect the brush pigtails from their contacts and circulate air through the units.
   2. Disconnect the brush pigtails from their contacts and discharge carbon dioxide into the units to keep them dry.
   3. Lift the brushes from commutator collector rings and use the built-in heater to prevent moisture accumulation.
   4. Lift the brushes from commutator collector rings and circulate cool dry air through the units.

ANS.: C

8. The direction of magnetic flux changes when the direction of current is reversed.
   1. True
   2. False

 ANS.: A

9. In a Transistor…
   1. PNP and NPN are two basic types
   2. Emitter, Collector and Base are the basic Elements.
   3. Collector separates Base and Emitter
   4. Emitter separates Base and Collector

ANS.: B

10. If a Motor is not rotating in the E/R, you will carry out the following Checks
    1. Check for the isolation
    2. Check for the Circuit breaker
    3. Remove the fuses
    4. Look for the Overload Trip

ANS.: 1,2,3,4

11. If a Motor is not rotating in the E/R, you will carry out the following Checks
    1. Rotate the Coupling with your hand
    2. Visually Inspect the Starter Terminals
    3. Look for the Overload Trip
    4. Remove the fuses

ANS.: 1,2,3,4

12. If a Motor is not rotating in the E/R, you will carry out the following Checks
    1. Check for the Circuit breaker
    2. Carry out Infinite Resistance Test
    3. Visually inspect the motor terminals
    4. Check for the isolation

ANS.: 1,2,3,4

13. Arrange the following in Increasing Order of their Doping Strength.
    1. Collector, Emitter, Base
    2. Base, Collector, Emitter
    3. Emitter, Base, Collector
    4. Emitter, Collector, Collector Base, Collector, Base

ANS.: B

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

ANS.: A,B,C

15. A molded-case breaker provides protection against short-circuits by using a/an
    1. Shading coil.
    2. Arc quencher.
    3. Holding coil.

ANS.: C

16. PN diode advantage over vacuum diode?
    1. Longer Life,
    2. No warm up time
    3. Less delicate
    4. All of the above

ANS.: D

17. Time delayed or delayed action-type fuses are designed to _____________.
    1. Prevent grounds in branch circuits
    2. prevent opens in motor circuits
    3. permit momentary overloads without melting
    4. guard lighting and electronic circuits

ANS.: C

18. Silicon diodes designed for a specific reverse breakdown voltage, become useful as an electronic power supply voltage regulator, called ___________
    1. Tunnel diodes
    2. hot-carrier diodes
    3. compensating diodes
    4. Zener diodes

ANS.: D

19. Which of the following statements best describes the material known as varnished cambric?
    1. Felted asbestos sealed with varnish.
    2. Cotton cloth coated with insulating varnish.
    3. Rubber insulation coated with a layer of tin.
    4. Paper impregnated with mineral oil, specially wrapped with nonmetallic tape, and coated with varnish.

ANS.: B

20. A synchronous motor maintains synchronism with the rotating field because
    1. Field strength varies directly with rotors IIel
    2. DC current applied to the rotor coils causes the rotor magnets to lock in with the rotating flux of the stator
    3. the stator poles are dragged around due to the flux created by the excitation current
    4. the stator flux rotates in the opposite direction

ANS.:  B

21. The part of a fuse that melts and opens the circuit is made of
    1. Copper and antimony
    2. Steel and Babbitt
    3. Aluminum or beryllium alloy
    4. Zinc or an alloy of tin and lead

ANS.: D

22. The apparent power in inductive circuit
    1. True power
    2. Lead
    3. Inductive
    4. Reactive

ANS.: D

23. If current reverses, the magnetic field also reverses; true (or) false
    1. TRUE
    2. FALSE

ANS.: B

24. Which of the listed precautions should take while cleaning poly phase motor internals with compressed air?
    1. Open the machine as both ends so as to allow the dust to escape
    2. Be certain that the circuit breaker is opened, tagged as the feeder panel
    3. Be certain that air is clean and as dry as possible
    4. Ensure that the fuse is removed

ANS.: A,B,C

25. Which of the following capacitor is having highest dielectric constant?
    1. Air gap
    2. Glass
    3. Paper
    4. Polyester

ANS.: B

26. A delayed action fuse is most frequently used in which of the listed circuit?
    1. Lighting circuit
    2. Motor circuit
    3. Electrical heater
    4. Radar circuit

ANS.: B

27. The current in a semiconductor is produced by
    1. Electrons
    2. Neutrons
    3. Protons
    4. Holes

ANS.: 1,4

28. 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
    1. Both decreases
    2. Increase and decrease
    3. Both increases
    4. Decrease and increase

ANS.: D

29. When the current through the coil of an electromagnet is reversed, the direction of magnetic field also reversed
    1. TRUE
    2. FALSE

ANS.: A

30. 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.
    1. Visually examine the motor for open circuit fault
    2. Visually examine the starter for open circuit fault
    3. Reverse the direction of current for its working
    4. Perform the infinite resistance test

ANS.: A,B,C