# Magnetic field in a D.C. generator is produced by?

Magnetic field in a D.C. generator is produced by electromagnets.

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## Related questions

Last Answer : Flashing the field of D.C. generator means creating residual magnetism by a D.C. source.

Last Answer : In a D.C. generator the magnetic neutral axis coincides with the geometrical neutral axis, when there is no load on|he generator.

Description : From which material field coils of DC generator are made of?

Last Answer : Field coils of DC generator are usually made of copper.

Description : A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave?

Last Answer : A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave will be of 5 Hz.

Last Answer : If brushes of a D.C. generator are moved in order to bring these brushes in magnetic neutral axis, there will be crossmagnetisation as well as demagnetising.

Last Answer : In a D.C. generator in case the resistance of the field winding is increased, then output voltage will decrease.

Description : A magnetic circuit has effective iron length of 100 cm and it is wound with 800 turns of wire carries 1 A. Find the magnetic field strength.

Last Answer : magnetic field strength

Description : What arc the errors occurring in measuring devices due to stray magnetic field and temp '? Explain how to compensate them.

Last Answer : 1. Error due to stray magnetic fields-   Main magnetic field gets disturbed by external magnetic fields known as stray magnetic fields.  2. Compensation technique   To avoid this error, ... resistance alloy having a negligible resistance temp coefficient in the ratio of 1:10 for pressure coil

Description : Derive an expression for energy stored in a magnetic field .

Last Answer : Expression for energy stored in a magnetic field: The energy is stored in magnetic field when current increases and return back when the current decreases. At instant t' seconds after closer of switch ... energy absorbed by the magnetic field when current increases from 0 to I amperes

Description : Define magnetic field strength and state its unit.

Last Answer : Magnetic field strength is the force experienced by a unit N-pole when placed at any point in a magnetic field is known as magnetic field strength or magnetizing force. Magnetising force or magnetic field ... unit of length is metre. So the unit of magnetic field strength is ampere turns per metre.

Description : Which of the following laws relates the magnetic field to the magnitude, direction, length, and proximity of the electric current? A) Lenz’s law B) Faraday’s law C) Biot–Savart law D) None of these

Last Answer : Which of the following laws relates the magnetic field to the magnitude, direction, length, and proximity of the electric current? A) Lenz’s law B) Faraday’s law C) Biot–Savart law D) None of these

Description : Which of the following statements is not characteristic of a static magnetic field? (A) It is solenoidal. (B) It is conservative. (C) It has no sinks or sources. (D) Flux lines are always closed.

Last Answer : Which of the following statements is not characteristic of a static magnetic field? (A) It is solenoidal. (B) It is conservative. (C) It has no sinks or sources. (D) Flux lines are always closed.

Last Answer : To avoid the effect of stray magnetic field in A.C. bridges we can use magnetic screening.

Description : How can a magnetic field be used to generate an electric current?

Last Answer : Magnetic  field  can  be  used  to  generate  electric  current  on  a  condition  that  it  is  on  a  rate  of  changing  magnetic  flux.  (Faraday's  law)

Last Answer : The critical resistance of the D.C. generator is the resistance of field.

Description : If residual magnetism is present in a D.C. generator, the induced e.m.f. at zero speed will be?

Last Answer : If residual magnetism is present in a D.C. generator, the induced e.m.f. at zero speed will be zero.

Last Answer : A 220 V D.C. generator is run at full speed without any excitation. The open circuit voltage will be about 2 V.

Last Answer : In a level compounded D.C. generator, full load terminal voltage is equal to no-load terminal voltage.

Last Answer : A D.C. generator can be considered as rotating amplifier.

Last Answer : In a D.C. generator, the critical resistance refers to the resistance of field.

Last Answer : If a D.C. generator fails to build up the probable cause could not be field resistance less than the critical resistance.

Last Answer : The e.m.f. generated in a D.C. generator is directly proportional to speed of armature.

Last Answer : In a D.C. generator the number of mechanical degrees and electrical degrees will be the same when number of poles is 2.

Last Answer : D.C. generator generally preferred for charging automobile batteries is long shunt compound generator.

Last Answer : The armature core of a D.C. generator is usually made of silicon steel.

Last Answer : In a D.C. generator the ripples in the direct e.m.f. generated are reduced by using carbon brushes of superior quality.

Last Answer : The demagnetising component of armature reaction in a D.C. generator reduces generator e.m.f.

Last Answer : In case of a 4-pole D.C. generator provided with a two layer lap winding with sixteen coils, the pole pitch will be 8.

Description : For a D.C. generator when the number of poles and the number of armature conductors is fixed, then which winding will give the higher e.m.f. ?

Last Answer : In a D.C. generator, the iron losses mainly take place in armature rotor.

Last Answer : The condition for maximum efficiency for a D.C. generator is variable losses equal to constant losses.

Last Answer : The total losses in a well designed D.C. generator of 10 kW will be nearly 500 W.

Last Answer : In D.C. generators on no-load, the air gap flux distribution in space is flat topped.

Last Answer : If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens this will make armature to take heavy current, possibly burning it.

Last Answer : If the field of a D.C. shunt motor gets opened while motor is running the motor will attain dangerously high speed.

Description : Field control of DC motor

Last Answer : Field control of DC motor

Description : The magnetic neutral plane shifts in a dc machine (A) in the direction of motion of motor (B) in the direction of motion of generator (C) due to increase in the field flux (D) cause reduction of flash over between commutator segments

Last Answer : The magnetic neutral plane shifts in a dc machine in the direction of motion of generator

Description : State the function of commutator in DC generator and name the material used for commutator.

Last Answer : Function of Commutator: Commutator converts AC induced in armature winding into DC for external load. Material: i) Commutator segments are made up of Copper. ii) Commutator segments are insulated from each other by Mica.

Description : A 200 V DC machine supplies 20 A at 200 V as a generator. The armature resistance is 0.2 Ohm. If the machine is now operated as a motor at same terminal voltage and current but with the flux increased by 10%, the ratio of motor speed to generator speed is

Last Answer : A 200 V DC machine supplies 20 A at 200 V as a generator. The armature resistance is 0.2 Ohm. If the machine is now operated as a motor at same terminal voltage and current but with the flux increased by 10%, the ratio of motor speed to generator speed is 0.87

Description : The fall in speed of a dc generator due to increase in load can be corrected by  (1) cooling the armature.. (2) increasing the excitation. (3) reducing the load voltage. (4) increasing the input to the prime mover

Last Answer : It   can  be  corrected  by  increasing  the  input  to  the  prime  mover.

Description : The eddy current loss in a dc generator is 400 W at 40 Hz frequency of reversal and constant flux density. When frequency is increased to 50 Hz., eddy current loss is :  (A) 256 W (B) 320 W (C) 500 W (D) 625 W

Last Answer : The eddy current loss in a dc generator is 400 W at 40 Hz frequency of reversal and constant flux density. When frequency is increased to 50 Hz., eddy current loss is : 625 W

Description : In a DC generator the windings of interpoles are connected :  (A) in series with main field winding, to create a pole,of same polarity as the main pole ahead in the direction of rotation.  ... winding, to create a pole of opposite polarity as the main pole ahead in the direction of rotation.

Last Answer : In a DC generator the windings of interpoles are connected :  in series with the armature winding, to create a pole of same polarity as the main pole ahead in the direction of rotation.

Description : The terminal characteristics of a dc generator suitable for electric welders is (A) separately excited generator (B) shunt generator (C) series generator (D) differentially compounded generator

Last Answer : The terminal characteristics of a dc generator suitable for electric welders is differentially compounded generator

Description : What is the difference between an AC and DC generator?

Last Answer : The generator which generates DC voltage is called DC generator and generator which generates AC voltage is called AC generator (or) Alternator. In DC generator armature is rotated and field winding ... generator. A DC generator can generate low voltages but an AC generator can generate upto 11kv.

Description : What is the principle of DC generator?