Online MCQ EE-Circuit Breakers Part Two

Instructions: Click the answer button to see the correct answer.

  1. The arc voltage produced in ac circuit breaker is
    1. In phase opposition to the arc current.
    2. lagging the arc current by 90°
    3. leading the arc current by 90°
    4. In phase with the arc current

    Answerd

  2. As the force on contact is increased, the contact resistance will
    1. increase exponentially
    2. remain unaltered
    3. increase linearly
    4. decrease.

    Answerd

  3. The heat produced at the contact point, due to passage of current, will least depend on
    1. temperature of the surrounding medium.
    2. current flowing
    3. contact resistance
    4. time during which the current flows

    Answera

  4. For the contact and their material, which of the following should have low value
    1. Thermal conductivity
    2. Thermal capacity
    3. Contact resistance
    4. All of the above.

    Answerc

  5. Minimum arcing voltage will be least in case of
    1. tungsten
    2. carbon
    3. silver.
    4. graphite

    Answerc

  6. Minimum arcing voltage for platinum is 16 V. It can be therefore concluded that when the voltage is below 16 V
    1. it will not be possible to interrupt the circuit
    2. it will be possible to interrupt any value of current without bringing contact closer to one another.
    3. it will be possible to interrupt any value of current without arcing
    4. it will not be possible to pass the current

    Answerc

  7. Oil immersion of contacts is the method of
    1. arc prevention
    2. none of the above.
    3. de ionization
    4. arc dispersion

    Answerd

  8. Which of the following is not the method of arc dispersion ?
    1. Oil immersion of contacts
    2. De ionization of arc path.
    3. Use of rectifiers
    4. Magnetic blow out of arc

    Answerc

  9. Which of the following contact point metals has the highest melting point ?
    1. Gold
    2. Silver
    3. Copper.
    4. Tungsten

    Answerd

  10. The arc voltage produced in the circuit breaker is always
    1. in phase with arc current
    2. all of these
    3. leading the arc current by 90°
    4. lagging the arc current by 90°

    Answera

  11. Ionization process during arc is generally accompanied by emission of
    1. light
    2. all of these
    3. heat
    4. sound

    Answerb

  12. Sparking between contacts can be reduced by
    1. inserting resistance in the line
    2. all of these
    3. inserting a capacitor in series with the contacts
    4. inserting a capacitor in parallel with the contacts.

    Answerd

  13. For magnetic blow out of arc the magnetic field is produced
    1. all of these
    2. parallel to the axis of the arc
    3. in the load circuit
    4. at right angles to the axis of the arc.

    Answerd

  14. Cool gases are solids brought into the arc stream assist in quenching the arc mainly by
    1. providing arc shield
    2. De ionization
    3. reducing current density
    4. providing parallel paths.

    Answerb

  15. Sparking occurs when a load is switched off because the circuit has
    1. high capacitance
    2. all of these
    3. high inductance
    4. high resistance.

    Answerc

  16. HRC fuses are
    1. High resistance and Capacitance fuses
    2. Heat reflecting cool fuses
    3. High rupturing capacity fuses.
    4. Holding and Resisting current fuses

    Answerc

  17. Which of the following metals does not amalgamate with mercury ?
    1. Tungsten
    2. Molybdenum
    3. All of these
    4. Nickel alloy

    Answerc

  18. For the same current, which of the following fuse wires will have the least fusing time ?
    1. 20 SWG TIN – 10 A
    2. 18 SWG TIN – 12.5 A
    3. 24 SWG TIN-5 A.
    4. 22 SWG TIN-7.5 A

    Answerc

  19. An automatic device that operates at present values is known as
    1. mercury switch
    2. relay
    3. contractor.
    4. fuse

    Answerb

  20. The basic function of a circuit breaker is to
    1. ionize the surrounding air
    2. produce the arc
    3. extinguish the arc.
    4. transmit voltage by arcing

    Answerc

  21. In
    a circuit breaker the arc is indicated by the process of I. Thermal
    emission II. Ionization of oil III. High temperature of air IV. Field
    emission

    1. I and II only
    2. I and IV only.
    3. I, II and III only
    4. II, III and IV only

    Answerb

  22. The power factor of the arc in circuit breaker is
    1. always leading.
    2. always unity
    3. always zero
    4. always lagging

    Answerb

  23. Air blast circuit breakers are usually used for
    1. permanent break
    2. repeated duty.
    3. intermittent duty
    4. instantaneous duty

    Answerb

  24. Flame proof switch gears are usually preferred
    1. substations
    2. in mines
    3. on transmission lines of low voltage
    4. in high MVA capacity circuits.

    Answerb

  25. Pressure of air in air blast circuit breakers is usually
    1. 1 – 5 kg/cm sqr
    2. 35-100 kg/cm sqr
    3. 10-30 kg/cm sqr
    4. 5 – 10 kg/cm sqr

    Answerc

  26. Air used in air blast circuit breaker
    1. must have oil mist
    2. must be free from moisture.
    3. must have least carbon dioxide
    4. must be ionized

    Answerb

  27. In a circuit breaker the time duration from the instant of fault to the instant of energizing of the trip coil is known as
    1. lag time
    2. operation time.
    3. lead time
    4. protection time

    Answerd

  28. In a circuit breaker the lime duration from the instant of the fault to the extinction of arc is known as
    1. lead time.
    2. total clearing time
    3. operation time
    4. lag time

    Answerb

  29. In a circuit breaker the lime duration from the instant of fault to the instant of closing of contact is known as
    1. Recycle time
    2. Re closing time.
    3. Total time
    4. Gross time

    Answerb

  30. For high speed circuit breakers the total lime is nearly
    1. Ten cycles.
    2. Few cycles
    3. One cycle
    4. Half cycle

    Answerd

  31. For a high speed circuit breaker the total clearing time is nearly
    1. 10 to 15 cycles
    2. less than 50 cycles.
    3. 1 to 2 cycles
    4. 5 to 10 cycles

    Answerc

  32. If the power factor is zero, the active recovery voltage will be
    1. minimum
    2. 0.707
    3. maximum.
    4. 0.5

    Answerc

  33. Which of the following is not a part of the circuit breaker ?
    1. Explosion pot
    2. Conservator
    3. Fixed and moving contacts
    4. Operating mechanism.

    Answerb

  34. A circuit breaker will normally operate
    1. Whenever fault in the line occurs.
    2. When the power is to be supplied
    3. When the line is to be checked
    4. When the switch is put on

    Answera

  35. Which of the following circuit breaker will produce the least arc energy ?
    1. All will produce same energy.
    2. Air blast circuit breaker
    3. Minimum oil circuit breaker
    4. Plain oil circuit breaker

    Answerb

  36. For a circuit breaker ‘break time’ is
    1. all of these
    2. opening time + arc duration
    3. opening time + arc duration + resistor current duration.
    4. same as opening time

    Answerc

  37. The breaking capacity of a circuit breaker in MVA (3 phase) is given by
    1. rated service voltage x rated symmetrical current
    2. √2x rated service voltage x rated symmetrical current.
    3. 1.1 x rated service voltage x rated symmetrical current
    4. √3x rated service voltage x rated symmetrical current.

    Answerd

  38. Which relay is used for feeders ?
    1. Buchholz relay.
    2. Merz price protection
    3. MHO relay
    4. Translay relay

    Answerd

  39. Which of the following relays is used on transformers ?
    1. Merz price relay
    2. Buchholz relay
    3. MHO relay
    4. None of these

    Answerb

  40. MHO relay is used for
    1. circuit breakers
    2. transmission lines
    3. feeders.
    4. rectifiers

    Answerb

  41. Merz-price protection is used on
    1. capacitor bank
    2. substations
    3. generators.
    4. induction motor

    Answerc

  42. The values of fault current depend on
    1. voltage at the faulty point and total impedance up to the fault
    2. none of these
    3. total impedance up to the fault
    4. voltage at the faulty point

    Answera

  43. The advantage of neutral earthing is
    1. all of these
    2. freedom from persistent arcing grounds
    3. simplified design of earth fault protection
    4. over-voltages due to lightning can be discharged to the earth

    Answera

  44. The over-voltage surges in power systems may be caused by
    1. resonance
    2. lightning
    3. any of these
    4. switching

    Answerc

  45. The protection against over-voltage due to lightening is provided by
    1. low tower footing resistance
    2. use of overhead ground wires
    3. any of these
    4. use of surge diverters

    Answerc

Copyright (C) 2016 by Circuit Breakers Part Two (ALL EXAM REVIEW ADDA)

Online MCQ EE-Circuit Breakers Part Three
ELECTRONICS AND COMMUNICATION ENGINEERING IMPORTANT MCQ-ELECTRICITY AND MAGNETISM FUNDAMENTALS (PART THREE)

2 Comments

  1. Ashish kaushik September 10, 2017
    • Harikesh Yadav September 11, 2017

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