Which of the following method of speed control of D.C. machine will offer minimum efficiency? A. Voltage control method B. Field control method C. Armature control method D. All ab... Which of the following method of speed control of D.C. machine will offer minimum efficiency? A. Voltage control method B. Field control method C. Armature control method D. All above methods. A D.C. series motor is that which? A. Has its field winding consisting of thick wire and less turns B. Has a poor torque C. Can be started easily without load D. Has almost constant speed.
Understand the Problem
The question is asking which method of speed control for a D.C. machine provides minimum efficiency and provides options for different methods of speed control. The second question is asking for characteristics that define a D.C. series motor.
Answer
Armature control method; thick wire and less turns.
For the first question, the armature control method offers minimum efficiency. For the second, a DC series motor typically has its field winding consisting of thick wire and less turns.
Answer for screen readers
For the first question, the armature control method offers minimum efficiency. For the second, a DC series motor typically has its field winding consisting of thick wire and less turns.
More Information
The armature control method is less efficient due to increased I²R losses from added resistance. A DC series motor is designed for high torque with thick wire to handle high current.
Tips
Avoid assuming all control methods equally affect efficiency; armature control introduces significant resistance losses.
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