online MCQ EE-TRANSFORMER PART ONE

TRANSFORMER PART ONE

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

  1. Eddy current loss will depends on
    1. All of these
    2. Flux density
    3. Thickness
    4. Frequency

    Answera

  2. Hysteresis loss will depends on
    1. f
    2. None of these

    Answerc

  3. Thin laminations are used in a machine in order to reduce
    1. Hysteresis losses
    2. None of these
    3. Eddy current losses
    4. Copper losses

    Answerc

  4. Hysteresis loop represents the area of
    1. hysteresis loss
    2. total iron losses
    3. copper loss
    4. eddy current loss

    Answera

  5. Total core loss is also called as ————-?
    1. Magnetic loss
    2. Hysteresis loss
    3. Eddy current loss
    4. Copper loss

    Answera

  6. Which of the following are variable losses?
    1. armature copper loss
    2. eddy current loss
    3. shunt field copper loss
    4. hysteresis loss

    Answera

  7. Maximum efficiency will occur, when copper loss is_______to iron loss?
    1. any of these
    2. equals to
    3. less than
    4. greater than

    Answerb

  8. The noise resulting from vibrations of lamination set by magnetic forces, is termed as
    1. zoom
    2. hum.
    3. boo
    4. magnetostriction.

    Answerb

  9. Auto transformer makes effective saving on copper and copper losses, when its transformation ratio is equal to
    1. less than one.
    2. very low
    3. approx to one.
    4. greater than one.

    Answerc

  10. Which of the following statements is/are correct?
    1. Both
    2. High frequency power supplies are light weight
    3. None of these
    4. Transformer size get reduced at high frequency

    Answera

  11. The basic function of a transformer is to change
    1. the power level
    2. the frequency
    3. the level of the voltage
    4. the power factor

    Answerc

  12. The frequency of a voltage at the secondary is
    1. less than primary
    2. equal to primary
    3. greater than the primary
    4. any of these

    Answerb

  13. Transformer action requires a
    1. alternating electric flux
    2. increasing magnetic flux
    3. constant magnetic flux
    4. alternating magnetic lux

    Answerd

  14. For an ideal transformer the winding should have
    1. no ohmic resistance on either side
    2. minimum resistance on primary side and maximum resistance on secondary side
    3. maximum resistance on primary side and least resistance on secondary side
    4. equal resistance on primary and secondary side

    Answera

  15. Which of the following statements is/are correct statements?
    1. all of these
    2. EMF per turn in both the windings are equal
    3. EMF per turn in HV winding is more than EMF per turn in LV winding
    4. EMF per turn in HV winding is less than EMF per turn in LV winding

    Answerb

  16. The core flux in transformer depends mainly on
    1. supply voltage
    2. supply voltage and load
    3. supply voltage, frequency and load
    4. supply voltage and frequency

    Answerd

  17. If
    the applied voltage of a certain transformer is increased by 50% and
    the frequency is reduced by 50%, the maximum flux density will (assuming
    that the magnetic circuit remains unsaturated)

    1. changes to 0.5 times the original value
    2. changes to 1.5 times the original value
    3. remain the same as the original
    4. changes to three times the original value

    Answerd

  18. The
    low voltage winding of a 400/230 V single phase 50 Hz transformer is to
    be connected to keep the magnetization current at the same level in
    both the cases the voltage at 25 Hz should be

    1. 460 V
    2. 115 V
    3. 230 V
    4. 65 V

    Answerb

  19. A
    single phase transformer has specifications as 250 KVA, 11000 V/415 V,
    50 Hz. What are the values of primary and secondary currents?

    1. primary = 602 A, secondary = 22.7 A
    2. primary = 22.7 A, secondary = 602.4 A
    3. primary = 301 A, secondary = 22.7 A
    4. primary = 11.4 A, secondary = 301 A

    Answerb

  20. R1
    is the resistance of the primary winding of the transformer. The turn
    ratio in terms of primary to secondary is K. Then the equivalent
    resistance of the primary referred to secondary is

    1. R1 /K²
    2. K²R1
    3. R1 /K
    4. K×R1

    Answera

  21. A
    5 KVA transformer has a turns ratio of N1/N2 = 10. The impedance of
    primary winding is 3+j5 ohms while that of secondary winding is 0.5+j0.8
    ohms. The impedance of transformer when referred to primary will be

    1. 3.5+j5.8 ohms
    2. 3.05+j5.08 ohms
    3. 53+j85 ohms
    4. 8+j13 ohms

    Answerc

  22. Voltage regulation of transformer is given by
    1. (V2 – E2) / V2
    2. (E2 – V2) / V2
    3. (E2 – V2) / E2
    4. (E2 – V2) / E2

    Answerd

  23. In a transformer zero voltage regulation is achieved at a load power factor which is
    1. zero
    2. leading
    3. lagging
    4. unity

    Answerb

  24. A
    transformer has resistance and reactance in per unit as 0.01 and 0.04
    respectively. Its voltage regulation for 0.8 power factor lagging and
    leading will be

    1. 3.2% and -1.6%
    2. none of these
    3. 6% and -4%
    4. 4.8% and -3.2%

    Answera

  25. The constant losses in transformer is/are
    1. hysteresis loss
    2. eddy current loss
    3. both hysteresis loss & eddy current loss
    4. copper loss

    Answerc

  26. In a transformer, hysteresis and eddy current losses depend upon
    1. maximum flux density
    2. supply frequency
    3. both supply frequency & maximum flux density
    4. load current

    Answerc

  27. In a transformer operating at constant voltage if the input frequency increases, the core loss
    1. none of these
    2. remains constant
    3. decrease
    4. increase

    Answerc

  28. If the frequency of input voltage of a transformer is increased keeping the magnitude of voltage unchanged, then
    1. Ph will increase but Pe will decrease
    2. Pe will increase but Ph will decrease
    3. both hysteresis loss(Ph) and eddy current loss(Pe) will increase
    4. Ph will decrease but Pe will remain same

    Answerd

  29. 1
    KVA, 230 V, 50 Hz, single phase transformer has an eddy current loss of
    30 watts. The eddy current loss when the transformer is excited by a dc
    source of same voltage will be

    1. 30 W
    2. less than 30 W
    3. more than 30 W
    4. zero watt

    Answerd

  30. A transformer has hysteresis loss of 30 W, at 240 V, 60 Hz. The hysteresis loss at 200 V, 50 Hz will be
    1. 30 W
    2. 25 W
    3. 28 W
    4. 36 W

    Answerb

  31. A
    single phase transformer when supplied from 220 V, 50 Hz has eddy
    current loss of 50 W. If the transformer is connected voltage of 330 V,
    75 Hz, the eddy current loss will be

    1. 168.75 W
    2. 112.5 W
    3. 75 W
    4. 50 W

    Answerb

  32. The
    full load copper loss and iron loss of transformer are 6400W and 5000W
    respectively. The copper loss and iron loss at half load will be
    respectively?

    1. 3200 W and 5200 W
    2. 3200 W and 2500 W
    3. 1600 W and 5000 W
    4. 1600 W and 1250 W

    Answerc

  33. Open circuit test on transformer gives
    1. hysteresis loss
    2. copper loss
    3. both eddy current loss & hysteresis loss
    4. eddy current loss

    Answerc

  34. Open circuit in a transformer is preferred with
    1. direct current
    2. rated transformer current
    3. high frequency supply
    4. rated transformer voltage

    Answerd

  35. In a transformer
    1. both OC and SC tests are conducted on LV side
    2. OC test is conducted on HV side and SC test is conducted on LV side
    3. both Oc and SC tests are conducted on HV side
    4. OC test is conducted on LV side and SC test is conducted on HV side

    Answerd

  36. In
    a single phase transformer the magnitude of leakage reactance is twice
    that of resistance of both primary and secondary. With secondary short
    circuited, the input power factor is

    1. 2/√5
    2. 1/√5
    3. 1/3
    4. 1/√2

    Answerb

  37. For a transformer to be tested at full load conditions but consuming only losses from the main, we do
    1. load test
    2. back to back test
    3. OC and SC tests
    4. none of these

    Answerb

  38. If
    Pi and Pc represent core and full load copper loss respectively, the
    maximum KVA delivered to load corresponding to maximum efficiency is
    equal to rated KVA is

    1. Pi/Pc
    2. (Pi/Pc)2
    3. √(Pi/Pc)
    4. Pc/Pi

    Answerc

  39. A transformer has maximum efficiency at 3/4 load. The ratio of iron loos and full load copper loss is
    1. 9/16
    2. 3/4
    3. 4/3
    4. 16/9

    Answera

  40. When
    a short circuit test on a transformer is performed at 25 V, 50 Hz, the
    drawn current is I1. If the test is performed by 25 V and 25 Hz and
    power drawn current is I2, then

    1. I1 < I2
    2. none of these
    3. I1 = I2
    4. I1 > I2

    Answera

  41. A
    2 KVA transformer has iron loss of 150 W and full load copper loss of
    250 W. The maximum efficiency of the transformer would occur when the
    total loss is

    1. 500 W
    2. 250 W
    3. 400W
    4. 300 W

    Answerd

  42. Silicon content in steel lamination is kept within 5% as it
    1. increases hysteresis loss
    2. makes the material brittle
    3. all of the above
    4. Increases cost

    Answerb

  43. The use of higher flux density in the transformer design
    1. increases the weigh per KVA
    2. reduces the weigh per KVA
    3. has no relation with the weight of transformer
    4. none of the above

    Answerb

  44. Transformer oil is used as
    1. a coolant
    2. inert medium
    3. both an insulator & an insulator
    4. an insulator

    Answerc

  45. Conservator tank is used
    1. for better cooling of transformer
    2. to take up the expansion of oil due to temperature rise
    3. to act as an oil storage
    4. none of these

    Answerb

  46. stepped cores are used in transformers in order to reduce
    1. reluctance of core
    2. volume of copper
    3. iron loss
    4. volume of iron

    Answerb

  47. Which is the arrangement of windings in a core type single phase transformer?
    1. Sandwiched lv and hv discs on each core limb
    2. Half hv inside and half lv outside on each core limb
    3. Half lv inside and half hv outside on each core limb
    4. Lv on one core limb and hv on the other

    Answerc

  48. A shell type transformer has
    1. none of these
    2. high eddy current loss
    3. neglegible hysteresis loss
    4. reduced magnetic leakage

    Answerd

  49. A
    100 KVA transformer is operating at 60 Hz, 240 V supply. The same
    transformer is operating at 50 Hz, 200 V supply. The new rating is

    1. 83.33 KVA
    2. 123.3 KVA
    3. 50 KVA
    4. 100 KVA

    Answera

  50. A
    transformer core is made up of a silicon steel laminations which has
    maximum flux density 1 Tesla. If it was cold rolled grain oriented its
    flux density increases to 1.6 Tesla. What is the saving in core size or
    area due to cold rolled grain oriented process?

    1. 38%
    2. 40%
    3. 60%
    4. 68

    Answera

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ONLINE MCQ EE-TRANSFORMER PART TWO
Problems on Ages PRACTICE SET 1 FOR RRVUNL AE & JE,UPPCL AE,DMRC/NMRC,SSC JE,BSPHCL JE

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