The speed control of universal motor used for sewing machines is by____________?
Correct answer: B. varying the resistance
- A. friction
- B. varying the resistance
- C. tapping the field
- D. centrifugal mechanism
Explanation
A sewing-machine universal motor commonly controls speed by inserting variable resistance in series with the motor, reducing the applied voltage and current. Field tapping is another possible method, but series resistance is the usual answer for this application.
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