**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?

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