# ELE152T : Unified Electrical Sciences - II Questions for Exam Practices

Question 1 : Define Efficiency of Transformers & also find its maximum efficiency condition.

Question 2 : How to test the transformers? Explain.

Question 3 : Explain the terms:
a)Losses
b)Core of transformer
c)transformation ratio

Question 4 : The no-load current of a transformer is 5.0 A at 0.3 power factor when supplied at 230 V, 50 Hz. The number of turns on the primary winding is 200.Calculate: (a) the maximum value of the ?ux in the core (b) the core loss (c) the magnetizing current.

Question 5 : The primary winding of a single-phase transformer is connected to a 230 V, 50 Hz supply. The secondary winding has 1500 turns. If the maximum value of the core ?ux is 0.002 07 Wb, determine: (a) the number of turns on the primary winding (b) the secondary induced voltage (c) the net cross-sectional core area if the ?ux density has a maximum value of 0.465 T.

Question 6 : How the flux density is changed when the conductor is moving inside magnet?

Question 7 : Derive the EMF equation of D.C machines.

Question 8 : Calculate the e.m.f. developed in the armature of a two-pole d.c. generator, whose armature has 280 conductors and is revolving at 100r/min. The ?ux per pole is 0.03 Wb.

Question 9 : A four-pole wave-connected armature has 51 slots with 12 conductors per slot and is driven at 900 r/min. If the useful ?ux per pole is 25 mWb, calculate the value of the generated e.m.f.

Question 10 : How the flux is distorted in D.C machine?