When the armature of a DC motor rotates emf induced is
A. Self induced.
B. Back emf.
C. Mutually induced emf.
D. None of above.
Show Answer
Answer: B
Share your understanding of this question with the correct explanation.
When the armature of a DC motor rotates, the electromotive force (emf) induced is referred to as back emf.
Back emf, also known as counter emf or armature reaction voltage, is the voltage generated in the armature winding of a motor due to its rotation in a magnetic field. As the armature rotates, the conductors within the armature winding cut through the magnetic field lines produced by the field winding. This cutting action induces a voltage in the armature winding according to Faraday’s law of electromagnetic induction.
In a DC motor, the back emf is opposite in polarity to the applied voltage. This is because the back emf opposes the change in current flow in the motor. It is called “back” emf because it acts against the applied voltage and reduces the net voltage across the motor.
The presence of back emf in a DC motor is important for its operation. It helps in regulating the motor speed by providing a counteracting voltage against the applied voltage. The magnitude of the back emf is proportional to the speed of the motor. As the motor speed increases, the back emf also increases, reducing the net voltage and controlling the motor’s speed.
Therefore, the correct answer is B: Back emf. When the armature of a DC motor rotates, the emf induced is referred to as back emf.