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(a) windings have no resistance, (b) core has no losses, (e) core has infinite permeability, (d) all of the above., 4, The main purpose of using core in.a transformer, isto, (a) decrease iron losses, (6) prevent eddy current loss, (e} climinate magnetic hysteresis, (d) decrease reluctance of the common magnetic circuit, , 5. Transformer cores are laminated in order to, (a) simplify its comstruction, (6) minimise eddy current loss, fe) reduce cost, (4) reduce hysteresis loss., , 6. A transformer having 1000 primary tums is, connected to a 250-V ac Supply. For a, secondary voltage of 400 V. the number of, secondary turns should be, (a) 1600 (4) 250, (e) 400 (d) 1250, , 7. The Pamaty and secondary induced e.m.fs, £, and Ein atw Winding transformer are alw ays, (4) equal in Magnitude, (5) antiphase with cach other, (€) in-phase with each other, @ ee by load on transformer second., , 8. A step-up transformer increases, (a) voltage, , Y, emf, power tum in primary,, (@) equal to K times, (6) equal to 1/K times, (ec) equal to, (d) greater than., In relation to a transformer, the ati 20: fing., cates that, , (a) there are 20 tums on primary One tang,, , secondary, (6) secondary voltage is 1/20th of prima, voltage, primary current is 20 Gmes greater thenty, secondary current,, “very 20 tums on primary, there ise, tum on secondary, he short circuit test of a mae, , high voltage side is usually short created, low voltage side is usually short circum, iny side is short circuited with prefertae, he of the above., Elect. Machines, AMAL. See. BUM, The equivalent resistance of the primary 8, tansformer having K = 5 and R, = 01 oe, when referred to secondary becomes., fa) 0.5, (6) 0.02, (e) 0.004, (d) 25, A.transformer has negative voltage veg, When its load power factor is, (@) zero, (5) unity, {c) leading, 4) lagging