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What is the effect of back emf in dc motor?
Back emf is very significant in the working of a dc motor. The presence of back emf makes the d.c. motor a self-regulating machine i.e., it makes the motor to draw as much armature current as is just sufficient to develop the torque required by the load.
How does the back emf affect the current flowing in the armature?
The high value of back emf decreases the armature current. The small magnitude of armature current develops less driving torque, which is equal to the load torque. And the motor will rotate uniformly at the new speed.
What is the formula for the back emf?
The back emf is calculated based on the difference between the supplied voltage and the loss from the current through the resistance. The power from each device is calculated from one of the power formulas based on the given information. The back emf is ϵi=ϵS−I(Rf+REa)=120V−(10A)(2.0Ω)=100V.
Why is the back EMF important in a DC motor?
Because the concept of back EMF in a DC motor is very essential for establishing the voltage equation of the motor. When we supply DC power to the DC motor, due to motoring action it starts rotating.
How does the magnitude of the back EMF decrease?
As the back emf depends on the current their value also decreases. The magnitude of the back EMF is nearly equal to the supply voltage. If the sudden load is applied to the motor, the motor becomes slow down. As the speed of the motor decreases, the magnitude of their back emf also falls down.
How is back emf induced in a generator?
Explain what back emf is and how it is induced. It has been noted that motors and generators are very similar. Generators convert mechanical energy into electrical energy, whereas motors convert electrical energy into mechanical energy. Furthermore, motors and generators have the same construction.
Why is a rotating coil called back EMF?
Any rotating coil will have an induced emf—in motors, this is called back emf, since it opposes the emf input to the motor.