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A field rheostat is used to control the current flowing through the field windings of a DC motor or generator. By adjusting the resistance, it alters the strength of the magnetic field, which in turn affects the speed and torque of the motor or the output voltage of the generator. This allows for fine-tuning of performance characteristics in various applications.

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Why the armature voltage E changes when the field rheostat is varied in shunt motors?

In shunt motors, the armature voltage ( E ) changes when the field rheostat is varied because altering the resistance in the field circuit affects the field current and, consequently, the magnetic flux produced by the field winding. When the field rheostat is decreased, the field current increases, leading to a stronger magnetic field and a higher back electromotive force (EMF) generated in the armature. This results in a change in the armature voltage, as the increased back EMF reduces the net voltage across the armature. Conversely, increasing the field resistance weakens the magnetic field, reducing back EMF and allowing the armature voltage to rise.


When to use a rheostat?

Depending on the situation. The purpose of the rheostat is use to change the resistance of the circuit. The rheostat is use to define Ohm Laws the 2nd situation is use to find out what the fixed resistor's resistance. 3rd purpose : used to control the resistance of circuit. eg Radio


Why the generator field rheostat kept at maximum position?

There is nothing to limit current until opposing magnetic fields build up at generator operating speed-windings will overheat and burn.


Can a rheostat be used to control speed on a capacitor run motor?

No. If you attempt to reduce the voltage to a cap start motor by using a rheostat, you can destroy the motor.


If the rheostat were connected in series with the shunt field winding and the combination placed across a 120 V dc line what shunt field current variations could be obtained from your motor?

It could be anything, it depends on the design of the motor and whether it is a high-power or a low-power motor.

Related Questions

Why the armature voltage E changes when the field rheostat is varied?

This depends on how the motor and wiring. You'll need to provide more information. Series / compound / shunt / differential / self or separately excited / is the rheostat in parallel or series to the field / is the rheostat on the shunt field or series field (if compound)


Why should the generator field rheostat be kept to its maximum at starting?

Keeping the generator field rheostat at its maximum at starting helps to establish a strong magnetic field in the generator, which is essential for generating sufficient voltage to initiate the generation process. This ensures a smooth and stable startup of the generator.


Why motor rheostat kept minimum position generator rheostat maximum position?

the back emf increases so that high currents doesn't pass through the field windings


What is the purpose of a rheostat in the determination of an unknown resistor?

A rheostat can be used to vary the resistance in a circuit until a balance condition is reached, allowing for the determination of the unknown resistor value through adjusting the resistance of the rheostat until the circuit is balanced. This process is often used in bridge circuits for precise resistance measurements.


Why the armature voltage E changes when the field rheostat is varied in shunt motors?

In shunt motors, the armature voltage ( E ) changes when the field rheostat is varied because altering the resistance in the field circuit affects the field current and, consequently, the magnetic flux produced by the field winding. When the field rheostat is decreased, the field current increases, leading to a stronger magnetic field and a higher back electromotive force (EMF) generated in the armature. This results in a change in the armature voltage, as the increased back EMF reduces the net voltage across the armature. Conversely, increasing the field resistance weakens the magnetic field, reducing back EMF and allowing the armature voltage to rise.


How do you Test a rheostat?

how to test a rheostat?


Who invented Rheostat?

The rheostat was invented by Sir Charles Wheatstone in the early 19th century. Wheatstone was a prominent English scientist and inventor who made significant contributions to the field of electrical engineering.


What is another name for a rheostat?

A variable resistor is another name for a rheostat.


Where does lost energy in a rheostat go?

It is lost in heating the resistive material of the rheostat.


What will happen if field rheostat of dc shunt motor is kept at maximum position while starting?

First remember this rheostat is connected in series with the armature to increase the total resistance to limit the starting current, thus achieving max starting torque from the motor


What is the hypothesis of a rheostat?

The hypothesis of a rheostat is that by changing the resistance in a circuit using the rheostat, the current flowing through the circuit can be varied, thus regulating the output of the circuit.


How do you install a rheostat in 1999 626 Mazda?

How do you install a rheostat in 1999 626 Mazda?