Auto-transformer makes effective saving on copper and copper losses, when its transformation ratio is_________________?

Related Mcqs:

1. The voltage transformation ratio of a transformer is equal to the ratio of_______________?

   A. primary turns to secondary turns
   B. secondary current to primary current
   C. secondary induced e.m.f. to primary induced e.m.f
   D. secondary terminal voltage to primary applied voltage

2. Which of the following is the main advantage of an auto-transformer over a two winding transformer?

   A. Hysteresis losses are reduced
   B. Saving in winding material
   C. Copper losses are negligible
   D. Eddy losses are totally eliminated

3. If R2 is the resistance of secondary winding of the transformer and K is the transformation ratio then the equivalent secondary resistance referred to primary will be___________?

   A. R2/VK
   B. R2IK2
   C. R22!K2
   D. R22/K

4. The full-load copper loss of a trans¬former is 1600 W. At half-load, the copper loss will be___________?

   A. 6400 W
   B. 1600 W
   C. 800 W
   D. 400 W

5. In a given transformer for given applied voltage, losses which remain constant irrespective of load changes are______________?

   A. friction and windage losses
   B. copper losses
   C. hysteresis and eddy current losses
   D. none of the above

6. Reduction in core losses and increase in permeability are obtained with transformer employing__________?

   A. core built-up of laminations of cold rolled grain oriented steel
   B. core built-up of laminations of hot rolled sheet
   C. either of the above
   D. none of the above

7. In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are__________?

   A. hysteresis and eddy current losses
   B. friction and windage losses
   C. copper losses
   D. none of the above

8. The changes in volume of transformer cooling oil due to variation of atmospheric temperature during day and night is taken care of by which part of transformer?

   A. Conservator
   B. Breather
   C. Bushings
   D. Buchholz relay

9. Which of the following statements regarding an idel single-phase transformer having a turn ratio of 1 : 2 and drawing a current of 10 A from 200 V A.C. supply is incorrect?

   A. Its secondary current is 5 A
   B. Its secondary voltage is 400 V
   C. Its rating is 2 kVA
   D. Its secondary current is 20 A
   E. It is a step-up transformer

10. In a transformer the resistance between its primary and secondary is____________?

    A. zero
    B. 1 ohm
    C. 1000 ohms
    D. infinite