In case of a dc motor the ratio Eb / E is indicative of
A. efficiency.
B. ratio of input to output voltage.
C. ratio of starting to running torque.
D. ratio of starting to running current.
Answer: A
Share your understanding of this question with the correct explanation.
The correct answer is A. In the case of a DC motor, the ratio of back electromotive force (Eb) to the applied voltage (E) is indicative of the motor’s efficiency. This ratio is often referred to as the “voltage regulation” of the motor.
Efficiency in a motor is defined as the ratio of the output power to the input power. In the case of a DC motor, the output power is directly proportional to the back electromotive force (Eb) and the armature current (Ia), while the input power is given by the product of the applied voltage (E) and the armature current (Ia).
Therefore, the ratio Eb / E can be used to determine the efficiency of the motor, as it represents the proportion of the applied voltage that is effectively converted into back electromotive force. A higher value of Eb / E indicates a more efficient motor, as a larger portion of the input voltage is utilized to generate the back electromotive force.