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Q: Derive emf equation of a DC machine?
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What is the factors determining induced emf in dc machine?

In simple, number of turns of armature, intensity of magnet and speed of machine are major factor affecting induced emf in dc generator. If speed is increased, voltage will be increased simultaneously. Also Voltage is greater if number of turns are increased. Electro-magnet in the poles of a DC Generator also play an important role in the induced EMF. If intensity of magnet is exceeds, voltage also increased as well.


What is Back emf of DC motor?

In dc motor, the armature conductors are revolving in the magnetic field and emf is induced in the armature conductors. The direction of the induced emf is in opposite direction to the applied voltage as per Flemings left hand rule. So, the induced emf in motor is called as back emf or counter emf. Vydehi


Why is a starting current in a DC motor very high?

A rotating d.c. motor generates a back-emf which opposes the supply voltage and reduces the current drawn by the motor. When the motor is stationary, it cannot generate this back emf and, so, the only opposition to current is the resistance of its windings which is relatively low. So, on startup, the current is large; as the machine starts to run, the resulting back emf, acts to reduce the current.


What motor is NOT suitable for use as a DC machine?

What motor is NOT suitable for use as a DC machine?


What is the function of a commutator in DC generator?

All types of generators induce EMF in sinusoidal wave form. (A.C.) In a D.C. generator the function of a commutator is to convert A.C. EMF into D.C. The commutator rectifies the output that is the alternating current so as to produce unidirectional alternating current (pulsating DC). This reverses the negative polarity current to a positive one so as the output is a pulsating DC.

Related questions

Derive the equation for average value of DC?

The equation for the average over time T is integral 0 to T of I.dt


When pole flux of dc motor is zero what is its speed?

when the pole flux is zero there is no induced emf in the armature conductor of dc machine as a result of this there is no back emf for controlling action so speed become dangerously high or we can say it will be infinite.


What is the difference between a DC motor and a generator in terms of EMF?

During the operation of a DC motor, EMF is created across its terminals using an external source. Whereas, in a DC generator EMF is created across its terminal based on principle of dynamically induced EMF. So talking in terms of EMF, in DC motor EMF is consumed by the motor coil and utilized to rotate the axle. On the other hand, in DC generator EMF developed across coil is transfered to a load or a battery and consumed by them.


The back emf indcuced in the armature is AC or DC?

only in dc motor...


What is the factors determining induced emf in dc machine?

In simple, number of turns of armature, intensity of magnet and speed of machine are major factor affecting induced emf in dc generator. If speed is increased, voltage will be increased simultaneously. Also Voltage is greater if number of turns are increased. Electro-magnet in the poles of a DC Generator also play an important role in the induced EMF. If intensity of magnet is exceeds, voltage also increased as well.


What is the EMF for DC machines?

Electro Magnetic Field


What is Back emf of DC motor?

In dc motor, the armature conductors are revolving in the magnetic field and emf is induced in the armature conductors. The direction of the induced emf is in opposite direction to the applied voltage as per Flemings left hand rule. So, the induced emf in motor is called as back emf or counter emf. Vydehi


Why back emf effect is vanished in case of inductor if dc input is given?

The fluctuation of the AC which sets up an magnetic field and causes a reverse emf is lost with DC because there is no variation in the field.


What does an increase in field strength in a dc generator causes a?

increased Back emf


How much emf is needed for running a dc motor?

It depends entirely on the design of the motor.


Why a dc generator you unable to generate emf even its armature is rotating?

bad connection


What is the difference between Counter-electromotive force and back emf?

They are Same for dc motor