silicon steel.
wrought iron.
cast iron.
cast steel.

Electrical Machines The brush-axis of a bipolar dc motor is rotated by 90°. The effect of this rotation on the back emf Eband the torque developed Tdwould be such that

both Eb and Td are unchanged
Eb is unchanged, but Td is zero
Eb is zero, but Td is unchanged
both Eb and Td are zero

Electrical Machines For successful parallel operation of two single phase transformers, the most essential condition is that their

polarities are properly connected
percentage impedances are equal
KVA ratings are equal
turn- ratios are exactly equal

Electrical Machines Which of following components of a DC generator plays vital role for providing direct electric current of a DC generator?

Equalizer rings.
Commutator.
Eye bolt.
Dummy coils.

Electrical Machines Consider the following statements about commutating poles which are fitted on most large dc Shunt motors: 1. The commutating poles are placed in the geometric neutral plane and their number is usually Equal to the number of main poles 2. The winding on the commutating poles is connected in series with the shunt-field winding on the main poles 3. The polarity of the commutating pole must be that of the next pole further ahead 4. The commutating poles neutralize the reactance voltage produced in the coil undergoing Commutation. Of these statements,

1, 2 and 3 are correct
2, 3 and 4 are correct
1 and 4 are correct
1, 2 and 4 are correct

Electrical Machines Scott connections are used for

any of the above.
three phase to single phase transformation.
single phase to three phase transformation.
three phase to two phase transformation.