Theoretically, If Eb = V in a DC motor, the motor is likely operating at ______.
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A.
a stalled condition
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B.
no load
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C.
overload
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D.
full load
Correct Answer:
B. no load
Explanation:
In a DC motor, the back electromotive force (Eb) is the voltage generated by the armature as it rotates through a magnetic field, and it directly opposes the supplied terminal voltage (V). The relationship between these values and the armature current (Ia) is defined by the equation V - Eb = Ia * Ra, where Ra represents the resistance of the armature.
Theoretically, if the back EMF equals the applied voltage (Eb = V), the net voltage in the circuit becomes zero, resulting in a negligible armature current. This state occurs when the motor is operating at no load. In this condition, the absence of an external load allows the motor to reach its maximum possible speed, which in turn generates a back EMF that is nearly equal to the supply voltage. Therefore, the motor is likely operating at a no-load condition.
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