## electrician

### MCQ ON ELECTRICAL TRANSFORMER PAGE - 1

1.
 The basic function of a transformer is to change A The level of the voltage B The power level C The power factor D The frequency Answer : A Explanation :
2.
3.
 In an ordinary transformer which of the following does not change A Voltage B Current C Frequency D All of the above Answer : C Explanation :
4.
 Transformer action requires a A Constant magnetic flux B Increasing magnetic flux C Alternating magnetic flux D Alternating electric flux Answer : C Explanation :
5.
 The primary and secondary  windings of a power transformer always have A A common magnetic flux B Separate magnetic circuits C Wire of same size D Same number of turns Answer : A Explanation :
6.
 On removing the cores of a transformer, the production of magnetic flux: A Is reduced B Is increased C Is increased D None of these Answer : A Explanation :
7.
 In a transformer, the linkage of magnetic flux takes place from: A Primary to secondary B Secondary to primary C Primary to secondary and from secondary to primary D None of these Answer : C Explanation :
8.
 Since the cores of a transformer are made of silicon steel therefore: A Copper loss remains low B Eddy current loss remains low C Hysteresis loss remains low D Both copper and eddy current losses remain low Answer : C Explanation :
9.
 The efficiency of transformer stands high because A It works on the principle of mutual induction B It is a static instrument C Its windings remain immersed in the mineral oil D There is no loss of electric power in it. Answer : B Explanation :
10.
 For equal capacity a shell type transformer as compared to a core type transformer will have A Low copper loss B Low iron loss C Low copper and iron losses D High copper and iron losses Answer : B Explanation :
11.
 If the supply frequency of a transformer is reduced then it iron loss will be: A Low B High C The same D Very high Answer : A Explanation :
12.
 If the transformers have different voltage ratios (Ep/Es) and their parallel operation is desired then A They will not work on load B They will not work at all C They will work at different power factors D They will work at an average voltage Answer : B Explanation :
13.
 The capacity of a star connected transformer as compared to a delta connected transformer will be A 3 times B 1/3 times C ½ times D Equal Answer : B Explanation :
14.
 In the breather of a transformer, silica – jelly is used to stop the _____to reach upto the insulating oil A Rain water B Dry air C Moisture D Steam Answer : C Explanation :
15.
 The principle of working of a transformer is A Static induction B Self induction C Mutual induction D Dynamic induction Answer : C Explanation :
16.
 A transformer is used for changing the value of A Voltage B Frequency C Power D Power factor Answer : A Explanation :
17.
 A transformer operates A Always at unity power factor B At its own power factor C At a power factor below a particular value D At a power factor depending on the power factor of the load. Answer : D Explanation :
18.
 The reactance of a transformer is determined by its: A Common core flux B Leakage flux C Size of the core D Permeability of the core material Answer : B Explanation :
19.
 The efficiency of a transformer is normally in the rnage of A 50 % to 70% B 60% to 75 % C 80 % to 90% D 90% to 98% Answer : D Explanation :
20.
 Eddy current loss in a transformer can be reduced by A Increasing the thickness of the laminations B Decreasing the thickness of the laminations C Winding the coils with a higher gauge wire D Decreasing the air gap in the magnetic circuit Answer : B Explanation :
21.
 The main property of a transformer is this that it changes the voltage level of an ac signal A Without changing it power B Without changing it frequency C Without changing it shape D Without changing its power, frequency and shape Answer : D Explanation :
22.
 Transformers are rated in A kW B kV C kWh D KVA Answer : D Explanation :
23.
 What type of core is used in a transformer designed to work at high frequencies (MHz range)? A Aluminum core B Iron core C Air core D Open type iron core Answer : C Explanation :
24.
 If  the secondary turns of a transformer are doubled and at the same time the primary voltage is reduced to half then the secondary voltage will: A Be halved B Be doubled C Not change D Be four time high Answer : C Explanation :
25.
 The no-load current of a transformer in terms of full load current is usually A 1% to 3% B 3% to 9% C 9% to 12% D 12% to 20 % Answer : B Explanation :
26.
 The transformer oil used in transformers provide: A Cooling and lubrication B Insulation and lubrication C Insulation and cooling D Insulation cooling and lubrication Answer : C Explanation :
27.
 Which is the common method of a cooling a power transformer used in distribution work? A Air cooling B Air blast cooling C Oil cooling D Water cooling Answer : C Explanation :
28.
 What is the typical use of an auto - transformer? A to work as a control transformer B to work as a variable transformer C to work as a distribution transformer D to work as an isolating transformer Answer : C Explanation :
29.
 As compared to an amplifier a transformer cannot A Increase output power B Increase output voltage C Increase output current D None of these Answer : A Explanation :
30.
 A conservator used in a transformer consist of A An air tight metallic drum fixed at the top of the oil tank B An air tight metallic drum fixed at the bottom of the oil tank C Overload protection device D None of these Answer : A Explanation :
31.
 In a power transformer, the winding nearer to the iron core A Is a high voltage winding B Is a low voltage winding C May be low or high voltage winding D The two types of windings are placed in a sandwich manner Answer : C Explanation :
32.
 A good transformers oil should be free from A Sulphur B Alkali C Moisture D All the above Answer : D Explanation :
33.
 The two transformers operated in parallel will share the load depending  upon their  : A Rating in kVA B Efficiency C Leakage reactance D Per unit impedance Answer : D Explanation :
34.
 In an ideal transformer, the no-load primary current Io: A Is in phases with Vp B Lags behind Vp by 900 C Leads Vp by 900 D Lags Vp by an angle lying between 00 and 900. Answer : A Explanation :