Transformer MCQ Questions and Answers

181. Which parameter does not change during transformation action in a transformer?

  1. Voltage
  2. Frequency
  3. Current
  4. None of these
Answer
Answer. b

182. A 10 kVA, 400V/200V, single-phase transformer with 10% impedance, draws a steady short circuit current of

  1. 50 A
  2. 150 A
  3. 250 A
  4. 350 A
Answer
Answer. c

183. The transformer laminations are insulated from each other day

  1. Mica strip
  2. Thin coat of varnish
  3. Paper
  4. Any of the above
Answer
Answer. b

184. Iron loss of a transformer can be measured by

  1. Low power factor wattmeter
  2. Unity power factor wattmeter
  3. Frequency meter
  4. Any type of wattmeter
Answer
Answer. a

185. In an actual transformer, the iron loss remains practically constant from no load to full load because

  1. Value of transformation ratio remains constant
  2. Permeability of transformer core remains constant
  3. Core flux remains practically constant
  4. Primary voltage remains constant
Answer
Answer. c

186. In the supply frequency to the transformer is increased, the iron loss will

  1. Not change
  2. Decrease
  3. Increase
  4. Any of the above
Answer
Answer. c

187. When a given transformer is run at its rated voltage but the reduced frequency, its

  1. Flux density remains unaffected
  2. Iron losses are reduced
  3. Core flux density is reduced
  4. Core flux density is increased
Answer
Answer. d

188. Power transformers are generally designed to have maximum efficiency around

  1. No-load
  2. Half-load
  3. Near full-load
  4. 10% overload
Answer
Answer. c

189. Which winding of the transformer has less cross-sectional area?

  1. Primary winding
  2. Secondary winding
  3. Low voltage winding
  4. High voltage winding
Answer
Answer. d

190. Two transformers operating in parallel will share the load depending upon their

  1. Leakage reactance
  2. Per unit impedance
  3. Efficiencies
  4. Ratings
Answer
Answer. b

191. Two power transformer is a constant

  1. Voltage device
  2. Current device
  3. Power device
  4. Main flux device
Answer
Answer. d

192. The purpose of providing iron core in a step-up transformer is

  1. To provide coupling between primary and secondary
  2. To increase the magnitude of mutual flux
  3. To decrease the magnitude of magnetizing current
  4. To provide all the above features
Answer
Answer. c

193. The no-load current of a transformer

  1. Has high magnitude and low power factor
  2. Has high magnitude and high power factor
  3. Has small magnitude and high power factor
  4. Has small magnitude and low power factor
Answer
Answer. d

194. Transformer breathes in when

  1. Load on it increases
  2. Load on it decreases
  3. Load remains constant
  4. None of the above
Answer
Answer. b

195. Delta-star transformer works satisfactorily when

  1. Load is balanced only
  2. Load is unbalanced only
  3. On balanced as well as unbalanced loads
  4. None of the above
Answer
Answer. c

196. Star-star transformers work satisfactorily when

  1. Load is unbalanced only
  2. Load is balanced only
  3. On balanced as well as unbalanced loads
  4. None of the above
Answer
Answer. b

197. The degree of mechanical vibrations produced by the laminations of a transformer depends on

  1. Size of laminations
  2. Gauge of laminations
  3. Tightness of clamping
  4. All of the above
Answer
Answer. d

198. A transformer is connected to a constant voltage supply. As the supply frequency increases, what happens to the magnetic flux in the core?

  1. Decreases
  2. Increases towards saturation
  3. Becomes zero
  4. Become constant
Answer
Answer. a

199. The efficiency of a transformer at full load, 0.8 pf lagging is 95%. What will its efficiency at full load, 0.8 pf leading be?

  1. 85 %
  2. 90 %
  3. 95 %
  4. 100 %
Answer
Answer. c

200. When a sinusoidal exciting current is applied to a transformer, what is the mutual flux produced?

  1. Flat tap
  2. Sinusoidal
  3. Zero
  4. Second harmonic only
Answer
Answer. b
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