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5 DC Motors > MULTIPLE-CHOICE QUESTIONS AND ANSWERS

MULTIPLE-CHOICE QUESTIONS AND ANSWERS

1. The back emf of a motor at the time of starting is

(a) zero (b) maximum (c) minimum (d) optimum

2. In a series motor, the field flux is

  • (a) proportional to the armature current
  • (b) is nearly constant
  • (c) inversely proportional to the armature current
  • (d) proportional to the square of the armature current

3. Series motors have a relatively

(a) high starting torque (b) medium starting torque
(c) low starting torque (d) a zero starting torque

4. If the field current of a shunt motor is changed, then

  • (a) its torque remains constant but the horsepower changes
  • (b) horsepower remains constant but the torque changes
  • (c) both torque and horsepower change
  • (d) both torque and horsepower remain constant

  

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