# Why field current has low values when compared to armature current

## Related Questions

Description : As compared to shunt and compound DC motors, the series DC motor will have the highest torque because of its comparatively ____________ at the start. (A) Lower armature resistance. (B) Stronger series field. (C) Fewer series turns. (D) Larger armature current.

Last Answer : (D) Larger armature current.

Description : a dc generator has a terminal voltage of 250V and an induced voltage of 262V when the generator is loaded. the brush drop is 1volt per brush and the armature resistance is 0.03 ohm ... reaction and determine the following: the load current the power of the load the percentage voltage regulation.

Last Answer : In a synchronous motor, the armature current has large values for high and low excitation.

Description : A three-phase synchronous motor has a terminal voltage of 460 V and a terminal current of 120 A at a power factor of 0.95 lagging, synchronous reactance of 1.68 ohm and the field current is 47 A. The field to armature mutual ... _____________.      (a). 20mH   (b). 16mH   (c). 24mH   (d). 22mH

Last Answer : 22

Description : A 4-pole, dc shunt motor working on 250V takes a current of 2A when running at no load on 1000 rpm. Calculate its back emf and speed at load if the motor takes 51A. Armature and shunt field resistance are 0.2Ω and 250Ω respectively

Description : Which of the following quantity maintains the same direction whether a D.C. machine runs as a generator or as a motor a. Induced e.m.f. b. Armature Current c. Field Current d. Supply Current

Last Answer : Which of the following quantity maintains the same direction whether a D.C. machine runs as a generator or as a motor a. Induced e.m.f. b. Armature Current c. Field Current d. Supply Current

Description : The domain in a gallium-arsenide semiconductor has what type of electrical field when compared to the other regions across the body of a semiconductor?

Last Answer : A field of much greater intensity.

Description : A dc cumulatively compounded motor delivers rated load torque at rated speed. If series field is short circuited, then the armature current and speed will a) Both increases b) Both decreases c) Increases and decreases d) Decreases and increases

Last Answer : Ans: Both increases

Description : In DC generators, armature reaction is produced actually by (A) Its field current. (B) Armature conductors. (C) Field pole winding. (D) Load current in armature.

Last Answer : Ans: D Because load current in armature gives rise to armature mmf which react with main field mmf.

Description : A field excitation of 20 A in a certain alternator results in an armature current of 400 A in short circuit and a terminal voltage of 2000 V on open circuit. The magnitude of the internal voltage drop within the machine at a load current of 200 A is  (A) 1 V (B) 10 V (C) 100 V (D) 1000 V

Last Answer : 800

Description : A 220 V dc machine has an armature resistance o f 1-ohm. If the full load current is 20A, the difference in the induced voltage when the machine is running as a motor, and as a generator is

Last Answer : A 220 V dc machine has an armature resistance o f 1-ohm. If the full load current is 20A, the difference in the induced voltage when the machine is running as a motor, and as a generator is 40 V.

Description : 1. If the current in the core decreases, what will the strength of the magnetic field be? 2. What is the commonly used unit for measuring the speed of data transmission? 3. The Govt. of ... flows between the Vindhya and Satpura ranges? 20. Which was a journal brought out by Abul Kalam Azad ?

Last Answer : Answer : 1. Decreases 2. Bits per second 3. Jeevan Sathi Yojana 4. Because warm and cold currents meet 5. Ranga II 6. Fatty tissue 7. Uttar Pradesh 8. Oil gas 9. Silvassa 10. Hunter 11. Sports ... 16. Speaker 17. Because of inadequate supply of air 18. Growth of GNP 19. Narmada 20. Al -Hilal

Description : With the help of neat diagrams,explain the following methods of speed control in DC series motor. i) Field diverter method. ii) Armature diverter method.

Last Answer : (i) Field diverter method: - Resistance connected in parallel with field winding -By adjusting this resistance current can by diverted from field winding -Thus field current decreases and the speed can be ... decreased, the flux must increase and hence speed is decreased than the rated speed.

Description : The supply both to field and armature circuits are disconnected simultaneously in a separately excited dc motor and it comes to a standstill in 5 sec. If the armature circuit of this motor is disconnected from supply with field ... rest in (1) 5 sec (2) 7 sec (3) 4 sec (4) A very long time

Last Answer : 5 sec only.standstill time doesn't depend upon field excitation

Description :  If shunt generator delivers 100 A at 200 V, and the resistance of the shunt field and armature are 100 ohm and 0.01 ohm respectively, the generated e.m.f. will be : -  a) 212 V b) 205 V c) 210 V d) 201.02 V

Last Answer :  If shunt generator delivers 100 A at 200 V, and the resistance of the shunt field and armature are 100 ohm and 0.01 ohm respectively, the generated e.m.f. will be : - 201.02 V

Description : A DC shunt generator supplies 450 A at 230 V. The resistances of shunt field and armature are 50 Ω and 0.025 Ω respectively. What will be the armature voltage drop?  (A) 11.24 V (B) 22.7 V (C) 31.6 V (D) 38.4 V

Description :  A 4-pole 460V shunt motor has its armature wave connected with 888 conductors. The   useful flux per pole is 0.02 wb and the resistance of the armature circuit is 0.7Ω. if the  armature current is 40A. Calculate  (i) the speed (ii) the torque

Description : main function of the current regulator is A. To prevent the reversal flow of current from the battery when dynamo speed is drops. B. To safeguard against flow of high currents to battery when armature develops ... . C. To prevent building up of high voltage in a circuit. D. None of the above

Last Answer : B. To safeguard against flow of high currents to battery when armature develops more current.

Description : A 50 kW dc shunt is loaded to draw rated armature current at any given speed. When driven  (i) at half the rated speed by armature voltage control and (ii) at 1.5 times the rated speed by field control, the respective output powers ... kW in (i) and 75 kW in (ii) (D) 50 kW in (i) and 50 kW in (ii)

Last Answer : A 50 kW dc shunt is loaded to draw rated armature current at any given speed. When driven  (i) at half the rated speed by armature voltage control and (ii) at 1.5 times the rated speed by field control, the respective output ... kW in (i) and 75 kW in (ii) (D) 50 kW in (i) and 50 kW in (ii)

Description : When running under no-load condition and with over excitation, armature current Ia drawn by a synchronous motor

Last Answer : When running under no-load condition and with over excitation, armature current Ia drawn by a synchronous motor Leads the applied voltage

Description : A 220 V shunt motor develops a torque of 54 N-m at armature current of 10 A. The torque produced when the armature current is 20 A, is?

Last Answer : Armature torque, Ta=PØZIa/2πA So Ta1/Ta2=Ia1/Ia2 Ta2=Ta1*Ia2/Ia1        =54*20/10         =108

Description : Compared to mild steel, cast iron has (i) High compressive strength (ii) High tensile strength (iii) Low compressive strength (iv) Low tensile strength The correct answer is (A) (i) and (ii) (B) (ii) and (iii) (C) (iii) and (iv) (D) (i) and (iv)

Description : The following is true of multidrug therapy of leprosy except: A. It has been highly successful in paucibacillary but not in multibacillary cases B. Relapse rate is very low in both paucibacillary ... use once a month D. Prevalence of lepra reaction is not higher compared to dapsone monotherapy

Last Answer : A. It has been highly successful in paucibacillary but not in multibacillary cases

Description : A conductor of length L has current I passing through it, when it is placed parallel to a magnetic field. The force experienced by the conductor will be (a) zero (b) BLI (c) B2LI (d) BLI2

Last Answer : (a) zero

Description : For aluminium, as compared to copper, all the following factors have higher values except (a) specific volume (6) electrical conductivity (c) co-efficient of linear expansion (d) resistance per unit length for same cross-section

Last Answer : (6) electrical conductivity

Description : If the load current and flux of a DC motor are held constant, and voltage applied across its armature is increased by 10%, its speed will:  (A) Decrease by 10%. (B) Remain unchanged. (C) Increase by 10%. (D) Increase by 20%.

Description : In an AC. circuit, a low value of kVAR compared with kW indicates?

Last Answer : In an AC. circuit, a low value of kVAR compared with kW indicates high power factor.

Description : A commutator in a d.c. machine (A) Reduces power loss in armature. (B) Reduces power loss in field circuit. (C) Converts the induced a.c armature voltage into direct voltage. (D) Is not necessary.

Last Answer : Ans: C As name suggests, it commutes ac into dc.

Description : In a d.c. machine, the armature mmf is (A) stationary w.r.t. armature. (B) rotating w.r.t. field. (C) stationary w.r.t. field. (D) rotating w.r.t. brushes.

Last Answer : (C) stationary w.r.t. field.

Description : In D.C. machines, ir order to prevent excessive distortion of field form by the armature reaction, the field mmf must be made (a) equal to that of armature mmf (b) less in comparison with the arma¬ture mmf (c) large in comparison with the arma-ture mmf (d) none of the above

Last Answer : (c) large in comparison with the arma-ture mmf

Description : The weight of copper of both armature and field windings decreases with _____ in number of poles. (a) increase (b) decrease (c) either of the above (d) none of the above

Last Answer : (a) increase

Description : cooling is the process of dissipating the armature and field winding losses to a cooling medium circulating within the winding insulation wall (a) Direct (b) Indirect (c) Conventional (d) Any ofthe above

Last Answer : (a) Direct

Description : Which of the following are the parts of a DC generator that convert the AC in the armature to DC in the external circuit. Are these parts the: w) field poles x) slip rings and the brushes y) commutator and the brushes z) armature and the core

Last Answer : ANSWER: Y -- COMMUTATOR AND THE BRUSHES

Description : For a DC motor, what major component in addition to the field winding and the armature winding is necessary? w) a commutator x) a stator y) a battery z) a rotor

Last Answer : ANSWER: W -- A COMMUTATOR

Description : In a synchronous machine, if the field flux axis ahead of the armature field axis in the direction of rotation, the machine is operating as  (1) synchronous motor (2) synchronous generator (3) asynchronous motor (4) asynchronous generator

Last Answer : In a synchronous machine, if the field flux axis ahead of the armature field axis in the direction of rotation, the machine is operating as synchronous generator

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.

Description : At low values of slip, the torque of an induction motor is   (a) directly proportional to the square of the slip. (b) inversely proportional to the square of the slip. (c) directly proportional to the slip. (d) inversely proportional to the slip.

Description : As compared to a CB amplifier, a CE amplifier has A) Lower current amplification B) Higher current amplification C) Higher input resistance. D) Both (B) & (C)

Last Answer : D) Both (B) & (C)

Description : A separately excited generator as compared to a self-excited generator (a) is amenable to better voltage con-trol (b) is more stable (c) has exciting current independent of load current (d) has all above features

Last Answer : Ans: d

Last Answer : When a conductor carries more current on the surface as compared to core, it is due to skin effect.

Description : Why is the Gramme-ring armature not more widely used

Last Answer : Only outside of coils cut flux (inefficient).

Description : Why are drum-type armatures preferred over the Gramme ring armature in modern dc generators?

Last Answer : Drum-type armatures are more efficient, because flux lines are cut by both sides of each coil.

Description : Why is the armature of DC generator laminated?

Last Answer : The armature of DC generator is laminated to reduce eddy current losses.

Description : A sine wave voltage is applied across an inductor. When the frequency of the voltage is decreased, the current decreases.

Last Answer : The question seems to be wrong. Increase in frequency would actually decrease the current through the Inductor. This happens because inductive reactance Xl is directly proportional to frequency. And if frequency increases the value of Xl would ... vice versa. Xl= 2*pi*f*L I=E/Z Z=sqrt(R^2+Xl^2)

Description :  A single phase, 2000V alternator has armature resistance and reactance of 0.8 ohm and 4.94 ohm respectively. The voltage regulation of the alternator at 100A, 0.8 leading pf is (A) 7% (B) - 8.9% (C) - 6.3% (D) 0%

Description : When excitation of synchronous motor is increased upto normal excitation from under excitation, armature current   (a) increases (b) decreases (c) remains constant (d) None of the above

Description : An input field takes the year of birth between 1900 and 2004 The boundary values for testing this field are A. 0,1900,2004,2005 B. 1900, 2004 C. 1899,1900,2004,2005 D. 1899, 1900, 1901,2003,2004,2005

Last Answer : C. 1899,1900,2004,2005

Description : Advantage of a clamp compared to a kiln for burning bricks is that (A) It takes less time for burning (B) It gives more output of first class bricks (C) It has less initial cost (D) It is suitable when bricks are required in large numbers