The speed of a DC series motor is
A. Proportional to the armature current.
B. Proportional to the square of the armature current.
C. Proportional to field current.
D. Inversely proportional to the armature current.
Answer: D
Share your understanding of this question with the correct explanation.
The speed of a DC series motor is inversely proportional to the armature current.
In a DC series motor, the speed is primarily determined by the balance between the electromagnetic torque produced by the interaction of the magnetic fields and the mechanical load on the motor. The electromagnetic torque is proportional to the product of the field current and the armature current.
When the armature current increases, the electromagnetic torque also increases. However, an increase in torque results in a greater mechanical load on the motor, which tends to decrease the speed. As a result, the speed of a DC series motor decreases as the armature current increases.
Therefore, the correct answer is D: inversely proportional to the armature current. The speed of a DC series motor is inversely proportional to the armature current.