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It doesn't. It exists in all electrical machines, d.c. or a.c., motor, generator, or transformer.
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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.
How do you prove the existence of back EMF?
How do you proof of the existence of back emf ?
Why two point starter used in dc series motor?
The only explanation to that is given by the presence of back emf Eb, which plays a critical role in governing the operation of the motor. The back emf, develops as the motor armature starts to rotate in presence of the magnetic field, by generating action and counters the supply voltage. This also essentially means, that the back emf at the starting is zero, and develops gradually as the motor gathers speed. The general motor emf equation E = Eb + Ia.Ra, at starting is modified to E = Ia.Ra as at starting Eb = 0.
Why we don't use starters for small motors?
When motor is started it has low speed which does not produce back emf hence very large current is drawn by the motor which may destroy the coil inside.small motors gain speed very quickly they produce back emf very fast at start hence they do not require starter.
What is the significance of back emf?
Back emf in a DC Motor plays a role of a regulator,We know the basic equation V=IaRa+Eb,where Ia,Ra are is the current through and resistance of the armature coil,Eb is the back emf and V is the Pd applied.Consider, Ia=V-Eb/Ra,The value of Ra is really small, just a few ohms and V would generally be around 240-220V(Indian conditions),assuming Eb to be zero(at the time of starting),it shows that Ia comes to be a really large value that the motor coil can barely handle,thats why we use a 3,2 POINT Starter that avoids large starting current,Now in the running condition of the motor Back emf would naturally be produced(say around 200V) this tends to reduce the value of(V-Eb), thus stopping a large current from entering the coil.But as the Load applied to the motor increases , Back emf would naturally come down to allow more current to enter the coil upto its rated value,to deliver the load requirement.thus Eb acts as a regulator.(Eb opposes the applied voltage)
The back emf indcuced in the armature is AC or DC?
only in dc motor...
What is emf induced in a motor's coil that tends to reduce the current in the coil of the motor?
BACK emf induced in a motor's coil that tends to reduce the current in the coil of the motor. The answer should be 'back'.
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 is the significance of emf?
According to motor eq. Eb=v-Ia.Ra.And the speed of motor is directly proportional to back EMF.At starting of motor speed is 0,so that Eb is also 0.As the speed increases ,Eb also increases,so that armature current decreases.As the Eb decreases ,so that Ia increases.In this way the back EMF makes the motor self regulating to take armature current as per requriment of motor.Because of this reason EMF also called governor principle of DC motor.This is most important significance of Back EMF. The back EMF is Explaned with lenses Law
What is significance of back emf?
According to motor eq. Eb=v-Ia.Ra.And the speed of motor is directly proportional to back EMF.At starting of motor speed is 0,so that Eb is also 0.As the speed increases ,Eb also increases,so that armature current decreases.As the Eb decreases ,so that Ia increases.In this way the back EMF makes the motor self regulating to take armature current as per requriment of motor.Because of this reason EMF also called governor principle of DC motor.This is most important significance of Back EMF. The back EMF is Explaned with lenses Law
What is the difference between Counter-electromotive force and back emf?
They are Same for dc motor
Can back emf in an inductor be in the same sense as emf of source?
yes..only the application is different.
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.
How do you prove the existence of back EMF?
How do you proof of the existence of back emf ?
Why two point starter used in dc series motor?
The only explanation to that is given by the presence of back emf Eb, which plays a critical role in governing the operation of the motor. The back emf, develops as the motor armature starts to rotate in presence of the magnetic field, by generating action and counters the supply voltage. This also essentially means, that the back emf at the starting is zero, and develops gradually as the motor gathers speed. The general motor emf equation E = Eb + Ia.Ra, at starting is modified to E = Ia.Ra as at starting Eb = 0.
When the load on a electric motor increased the current is also increased automatically why?
The approach to the answer depends on what kind of a motor we are discussing about.Whatever it is in a DC motor, there's an armature resistance, reactance (coil) and back e.m.f acting due to the spinning of motor (opposite the direction of the supply voltage)When a load (torque) is applied and increased, we can see that there is an opposite torque against the usual driving direction. (clockwise or anti CW).This results in a slight reduction in angular speed. But the back emf depends linearly on the speed of motor. So now, the speed is reduced & back emf is reduced. Now there's more resultant voltage applied across the armature resistance. (supply voltage (fixed) = (Varmature res. - back emf) ;; when back emf is reduced, Varmature res. is increased)Now, there is a rise in voltage across armature resistance causing a rise in current..
