Electrical Machines
Consider the following statements regarding the speed control of dc motors : 1. ward-leonard method is suitable forconstant-torque drives 2. Ward-leonard method is suitable for constant-power drives 3. field-control method facilitates speed control below base speed 4. Armature-resistance control method is more efficient than ward-leanard method 5. Field-control method is suitable for constant-torque drives 6. Armature-resistance control method is suitable for constant-torque drives From these, the correct answer is

 1, 2, 5
 1, 4, 6
 1, 2, 6
 1, 3, 5

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Electrical Machines
The speed of a DC series motor is

 Inversely proportional to the armature current.
 Proportional to the armature current.
 Proportional to field current.
 Proportional to the square of the armature current.

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