# If a D.C. motor is connected across the A.C. supply it will?

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If a D.C. motor is connected across the A.C. supply it will burn due to heat produced in the field winding by eddy currents.

## Related questions

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Last Answer : If a D.C. series motor is operated on A.C. supply, it will spark excessively, have poor efficiency, have poor power factor.

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Last Answer : A.C. series motor as compared to D.C. series motor has smaller brush width, less number of field turns, more number of armature turns, less air gap.

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Last Answer : Induction motor is a AC motor it is also known as asynchronous motor .

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Description : Consider a circuit with three parallel branches connected across a DC supply. What is the ratio of the branch currents I1 : I2 : I3 if the branch resistances are in the ratio of 2 : 3 : 4 respectively? A) 2 : 3 : 4 B) 6 : 4 : 3 C) 4 : 3 : 2 D) None of these

Last Answer : Consider a circuit with three parallel branches connected across a DC supply. What is the ratio of the branch currents I1 : I2 : I3 if the branch resistances are in the ratio of 2 : 3 : 4 respectively? A) 2 : 3 : 4 B) 6 : 4 : 3 C) 4 : 3 : 2 D) None of these

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Description : State the modification to be done in dc series motor to work satisfactorily as ac series motor. State applications of ac series motor.

Last Answer : Modifications are necessary in a dc series motor so that it operates satisfactorily on ac supply. The modifications are as follows:  1) AC series motor is built with a few field turns as ... and grinders 5) High speed vacuum cleaners 6) Sewing machines 7) Food processors 8) Drilling machine

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Last Answer : In a A.C. series motor armature coils are usually connected to commutator through resistance.

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Last Answer : At the instant of starting when a D.C. motor is put on supply, it behaves like a low resistance circuit.

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Last Answer : When a D.C. series motor is connected to A.C. supply, the power factor will be low because of high inductance of field and armature circuits.

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Description : What are the parts of AC motor?

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Description : What is the principle of AC motor?

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Description : AC motor

Last Answer : AC motor AC motor have two types one is Induction motor and second is synchronous motor. Induction motor have two types one is single phase induction motor and second is three phase ... self starting motor so using  external motor or we have to start it as induction motor.

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Description : Describe the reason of using dc series motor for electric trains.

Last Answer : Electric trains require an inverse torque speed characteristics for proper operation. That is a higher torque is required at start (when speed is nil or low) and as the train picks up ... torque - speed characteristics of DC series motors match, these motors are suitable for electric trains

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Description : A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5 W and the field winding resistance is 80 W. The net Voltage across armature resistance at the time of plugging will be

Last Answer : A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5 W and the field winding resistance is 80 W. The net Voltage across armature resistance at the time of plugging will be 474 V

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Description : A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance is 2 Ohm. It. is braked by plugging. The resistance to be connected in series with armature to restrict armature current to 10 A, is

Last Answer : A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance is 2 Ohm. It. is braked by plugging. The resistance to be connected in series with armature to restrict armature current to 10 A, is 36 Ohm

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Description : In a 2 kW, 200 V, 1000 rpm. DC series motor the torque at full load was found to be 0.3 N -m. The torque at half full load in N -m is :

Last Answer : In a 2 kW, 200 V, 1000 rpm. DC series motor the torque at full load was found to be 0.3 N -m. The torque at half full load in N -m is : 0.075

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Description : The function of a brush and commutator arrangement in a dc motor is to  (1) produce unidirectional torque (2) produce unidirectional current in the armature (3) help in changing the direction of rotation of the armature (4) reduce sparking

Last Answer : The function of a brush and commutator arrangement in a dc motor is to produce unidirectional torque

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Last Answer : If a D.C. motor designed for 40°C ambient temperature is to be used for 50°C ambient temperature, then the motor is to be derated by a factor recommended by manufacturer and select the next higher H.P. motor.

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Last Answer : For a D.C. shunt motor if the excitation is changed torque will change but power will remain constant.

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Description : The speed of a D.C. motor can be controlled by varying  1. Its flux per pole 2. Resistance of armature circuit 3. Applied voltage 4. All of the above

Last Answer : The speed of a D.C. motor can be controlled by varying  1. Its flux per pole 2. Resistance of armature circuit 3. Applied voltage 4. All of the above

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Last Answer : In case the back e.m.f. and the speed of a D.C. motor are doubled, the torque developed by the motor will remain unchanged.

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Last Answer : The speed of a D.C. shunt motor can be increased by increasing the resistance in field circuit.

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Description : As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit?

Last Answer : As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit a resistance is connected in series with armature.

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Last Answer : The armature voltage control of D.C. motor provides constant torque drive.

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Last Answer : The armature torque of the D.C. shunt motor is proportional to armature current.

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Last Answer : As the load is increased the speed of D.C. shunt motor will reduce slightly.

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Last Answer : In a differentially compounded D.C. motor, if shunt field suddenly opens the motor will first stop and then run in opposite direction as series motor.

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Last Answer : Flywheel is used with D.C. compound motor to reduce the peak demand by the motor, compound motor will have to be cumulatively compounded.

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Last Answer : Sparking, is discouraged in a D.C. motor because commutator gets damaged.

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Last Answer : D.C. Series motor is generally preferred for cranes and hoists.

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Last Answer : (b) Clostridium butylicum Lipase Removal of oil stains

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Last Answer : Sparking at the commutator of a D.C. motor may result in damage to commutator segments, damage to commutator insulation, increased power consumption.

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Last Answer : If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses.

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Last Answer : Cumulatively compounded D.C. motor will be suitable along with flywheel for intermittent light and heavy loads.

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Last Answer : The current drawn by the armature of D.C. motor is directly proportional to the torque required.

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Last Answer : In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to 25% of the previous value.

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Last Answer : The speed of a D.C. series motor is inversely proportional to the armature current.

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Last Answer : The starting resistance of a D.C. motor is generally low.

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Last Answer : In case the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be less than 50%.

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Last Answer : By looking at Commutator part of the motor, it can be easily confirmed that a particular motor is D.C. motor.

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Last Answer : In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be more than full-load current.

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Last Answer : The armature may burn if the back e.m.f. of a D.C. motor vanishes suddenly.

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Last Answer : In a D.C. shunt motor, speed is independent of armature current.

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Last Answer : The speed of a D.C. shunt motor more than its full-load speed can be obtained by decreasing the field current.

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Description : The type of D.C. motor used for shears and punches is?

Last Answer : The type of D.C. motor used for shears and punches is cumulative compound D.C. motor.

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Last Answer : For starting a D.C. motor a starter is required because it limits the starting current to a safe value.

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Last Answer : A D.C. series motor is that which has its field winding consisting of thick wire and less turns.

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