61. A transformer can have zero voltage regulation at
a. zero power factor
b. lagging power factor
c. leading power factor
d. unity power factor
62. The leakage impedance of primary and secondary of a transformer are ( 3 + j4 ) ohms and ( 1 + j4 ) ohms respectively . it can be concluded that the transformer has
a. low voltage primary
b. low voltage secondary
c. high voltage secondary
d. no conclusion can be drawn on the basis of the information given
63. The colour of dry silica gel is
a. pale yellow
b. pale pink
c. pale green
d. blue
64. The colour of most silica gel is
a. red
b. brown
c. blue
d. yellow
65. A transformer has a copper loss of 1.5% and reactance 3.5% when tested on load . it will have better regulation at
a. Unity power factor
b. 0.8 lagging p.f
c. 0.8 leading p.f
d. none of the above
66. In a 50 Kva transformer the number of turns in the primary and secondary winding are 834 and 58 respectively. If the primary is connected to 3300v. Supply the secondary current will be:
a. 15A
b. 30A
c. 218A
d. 438
67. In full load copper loss of transformer is 800w. its copper loss at 75% load will be:
a. 800w
b. 450
c. 400
d. 200
68. The essential condition for parallel operating of two single phase transformer is that they should have same
a. efficiency
b. capacity
c. voltage ratio
d. polarity
69. In a transformer the resistance between the primary and secondary must be
a. Zero
b. 1 K resistance
c. 100 K resistance
d Infinite
70. The secondary of a current transformer is always short circulated under operating conditions because
a. It avoid core saturation and high voltage induction
b. it avoid high voltage surges
c. it protects the primary cell
d. it is same for operation
