Question 248Electricity/Electronics - QMED70% to pass
The counter EMF of a DC motor is maximum when the _______________.
AI Explanation
The correct answer is D) motor is at rated speed.
The counter EMF (electromotive force) of a DC motor is maximum when the motor is running at its rated speed. This is because the counter EMF is directly proportional to the speed of the armature. As the motor reaches its rated speed, the armature rotates at its maximum velocity, generating the highest possible counter EMF.
The other options are incorrect because: A) the counter EMF is lower when the armature is not turning; B) the counter EMF increases as the motor approaches its rated speed, but is not yet maximum; and C) the counter EMF is lower when the armature has just begun to turn and is not yet at its maximum speed.
Related Questions
#246 In DC motor construction, where are the commutating windings wound? #247 Which of the following statements describes what will happen when both the polarity of the field poles, and the direction of current to the brushes of a DC motor are reversed? #249 What will happen if you reverse both the field and the armature connections of a DC propulsion motor? #250 What is an advantage of DC motors over AC motors? #251 Why are the armature cores of the DC motors constructed with laminated steel sheets?