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So, the back emf is directly proportional to speed. Hence, when the speed of a DC shunt motor is increased, then the back emf of the motor will increase.

## What will happen to the back emf of the motor if the speed of a DC shunt motor is made 1 by 5 of the original speed?

Explanation: In case of DC motor, the speed is proportional to the back emf (Ea ∝ N). So, with the increase in speed, the back emf also increases. Therefore, armature current is also decreased, in case of series motor, armature current is equal to the line or load current. 4.

## When the speed of a DC motor increases back emf?

Back emf is zero when the motor is not turning, and it increases proportionally to the motor’s angular velocity. Back emf is the generator output of a motor, and so it is proportional to the motor’s angular velocity ω.

## What will happen to torque if back emf and speed of the DC motor is doubled?

What will happen to torque if back emf and speed of the DC motor is doubled? Explanation: Torque depends on armature current, so as long as armature current remains constant torque will not change. Speed depends directly with back emf thus, it will definitely become double when back emf is doubled.

## What will happen if the increase in speed of a DC motor?

If the speed of a DC motor increases, there will be increase in back emf also. When the speed of a DC motor increases, emf will get increases and hence the current drawn will get decreases.

## What is the back emf in DC motor?

When the armature of the DC motor rotates under the influence of driving torque, the armature of the conductors moves through a magnetic field inducing an emf in them. The induced emf is in the opposite direction to the applied voltage and is known as the back emf.

## What will happen to a DC motor if its back emf is equal to the supply voltage?

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.

## What will happen if the back emf of a DC motor vanishes suddenly *?

Detailed Solution. If back emf of a dc motor vanishes suddenly, motor circuit will try to retain back emf by drawing more current from supply. As the back emf vanishes zero, the whole supply voltage appears across armature and heavy current flows.

## What causes back emf?

This back EMF is produced as a result of Lenz’s Law, which says that in a circuit with an induced EMF caused by a change in a magnetic field, the induced EMF causes a current to flow in the direction that opposes the change in flux. … Note that the magnetic field lines begin to collapse as the flow of electricity slows.

## How the back emf or counter EMF is produced?

A motor has coils turning inside magnetic fields, and a coil turning inside a magnetic field induces an emf. … This emf, known as the back emf, acts against the applied voltage that’s causing the motor to spin in the first place, and reduces the current flowing through the coils of the motor.

## Which emf is induced in the DC generator?

The emf induced in the dc generator armature winding is ac, but we need dc current from dc generator. So to convert this ac current to dc current mechanical rectifier called as commutator is used.

## What is the action of the induced emf in a running DC motor?

When the armature of a DC motor rotates under the influence of the driving torque, the armature conductors move through the magnetic field and hence emf is induced in them as in a generator. The induced emf acts in opposite direction to the applied voltage V (Lenz’s law) and is known as Back EMF or Counter EMF (Eb).

## Which determines the polarity of induced emf in DC shunt generator?

The number of conductors connected in series in each parallel path = Z/A. Thus, it is clear that the induced emf is directly proportional to the speed and flux per pole. The polarity of induced emf depends upon the direction of the magnetic field and the direction of rotation.

## Why is the speed of DC shunt motor dependent on back emf?

For d.c. shunt motor the speed is dependent on induced e.m.f. only because. Flux is proportional to armature current. Flux is practically constant in d.c. … Induced e.m.f. is equal to armature drop.

## What will happen to the RPM value when the voltage of DC motor power supply increases?

Increasing Voltage, Increases the Current Pulled, which Increases the Strength of the coil, which increases the RPM AND Torque of the motor.