Transformers – 1 – 2

6. A transformer having 1000 primary turns is connected to a 250-V a.c. supply. For a secondary voltage of 400 V, the number of secondary turns should be :

(a) 1600
(b) 250
(c) 400
(d) 1250

7. The primary and secondary induced e.m.fs. E1 and E2 in a two-winding transformer are always :

(a) equal in magnitude
(b) antiphase with each other
(c) in-phase with each other
(d) determined by load on transformer secondary

8.  If the primary power of an ideal transformer having a 2:1 voltage ratio is 100 W, the secondary power is :

(a) 50 W
(b) 75 W
(c) 100 W
(d) 200 W

9. In performing the short circuit test of a transformer :

(a) high voltage side is usually short circuited
(b) low voltage side is usually short circuited
(c) any side is short circuited with preference
(d) none of the above

10. A transformer has negative voltage regulation when its load power factor is :

(a) zero
(b) unity
(c) leading
(d) lagging

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