# Engineering/ Engineering Electrical Engineering Dc Motors part1 Sample Test,Sample questions

1.iip to 5 H.P.

2.up to 10 H.P.

3.up to 15 H.P.

4.up to 20 H.P.

## Question: `.If I2 be the armature currentthen speed of a D.C. shunt motor isindependent of Ia`

1.independent of Ia

2.proportional to la

3.varies as (Ia)

4.varies as la

## Question: `.In a D.C. shunt motorspeed is`

1.independent of armature current

2.directly proportional to the armature current

3.proportional to the square of the current

4.inversely proportional to the armature current

## Question: `.In a D.C. shunt motorunder the conditions of maximum powerthe current in the armature will be`

1.almost negligible

## Question: `.In case of D.C. shunt motors the speed is dependent on back e.m.f. only because`

1.back e.m.f. is equal to armature drop

2.armature drop is negligible

3.flux is proportional to armature current

4.flux is practically constant in D:C. shunt motors

## Question: `.The current drawn by the armature of D.C. motor is directly proportional to`

1.the torque required

2.the speed of the motor

3.the voltage across the terminals

4.none of the above

1.4

2.2

3.1

4.0.5

## Question: `.Which of the following method of speed control of D.C. machine will offer minimum efficiency ?`

1.Voltage control method

2.Field control method

3.Armature control method

4.All above methods

## Question: `.Which one of the following is not the function of pole shoes in a D.C. machine ?`

1.To reduce eddy current loss

2.To support the field coils

3.To spread out flux for better unifor-mity

4.To reduce the reluctance of the mag-netic path

## Question: `A D.C. series motor is that which`

1.has its field winding consisting of thick wire and less turns

2.has a poor torque

3.can be started easily without load

4.has almost constant speed

## Question: `A three point starter is considered suitable for`

1.shunt motors

2.shunt as well as compound motors

3.shuntcompound and series motors

4.all D.C. motors

1.Frame

2.Shaft

3.Commutator

4.Stator

## Question: `Differentially compound D.C. motors can find applications requiring`

1.high starting torque

2.low starting torque

3.variable speed

4.frequent on-off cycles

## Question: `For starting a D.C. motor a starter is required because`

1.it limits the speed of the motor

2.it limits the starting current to a safe value

3.it starts the motor

4.none of the above

## Question: `If a D.C. motor is connected across the A.C. supply it will`

1.run at normal speed

2.not run

3.run at lower speed

4.burn due to heat produced in the field winding by .eddy currents

## Question: `If a D.C. motor is to be selected for conveyorswhich rriotor would be preferred ?`

1.Series motor

2.Shunt motor

3.Differentially compound motor

4.Cumulative compound motor

## Question: `If the supply voltage for a D.C. motor is increasedwhich of the following will decrease ?`

1.Starting torque

2.Operating speed

4.All of the above

## Question: `In a D.C. series motorif the armature current is reduced by 50%the torque of the motor will be equal to`

1.100% of the previous value

2.50% of the previous value

3.25% of the previous value

4.10% of the previous value

## Question: `In case of conductively compensated D.C. series motorsthe compensating winding is provided`

1.as separately wound unit

2.in parallel with armature winding

3.in series with armature winding

4.in parallel with field winding

## Question: `In case-the conditions for maximum power for a D.C. motor are establishedthe efficiency of the motor will be`

1.100%

2.around 90%

3.anywhere between 75% and 90%

4.less than 50%

## Question: `In D.C. machines fractional pitch winding is used`

1.to improve cooling

2.to reduce copper losses

3.to increase the generated e.m.f.

4.to reduce the sparking

## Question: `In D.C. motor which of the following can sustain the maximum temperature rise?`

1.Slip rings

2.Commutator

3.Field winding

4.Armature winding

## Question: `In D.C. shunt motors as load is reduced`

1.the speed will increase abruptly

2.the speed will increase in proportion to reduction in load

3.the speed will remain almost/constant

4.the speed will reduce

## Question: `Sparking at the commutator of a D.C. motor may result in`

1.damage to commutator segments

2.damage to commutator insulation

3.increased power consumption

4.all of the above

## Question: `Sparkingis discouraged in a D.C. motor because`

1.it increases the input power con

2.commutator gets damaged

3.both (a) and (b)

4.none of the above

## Question: `Speed control by Ward Leonard method gives uniform speed variation`

1.in one direction

2.in both directions

3.below normal speed only

4.above normal speed only.

## Question: `Starters are used with D.C. motors because`

1.these motors have high starting torque

2.these motors are not self-starting

3.back e.m.f. of these motors is zero initially

4.to restrict armature current as there is no back e.m.f. while starting

## Question: `The condition for maximum power in case of D.C. motor is`

1.back e.m.f. = 2 x supply voltage

2.back e.m.f. = | x supply voltage

3.supply voltage = | x back e.m.f.

4.supply voltage = back e.m.f.

## Question: `The direction of rotation of a D.C. series motor can be changed by`

1.interchanging supply terminals

2.interchanging field terminals

3.either of (a) and (b) above

4.None of the above

## Question: `The power mentioned on the name plate of an electric motor indicates`

1.the power drawn in kW

2.the power drawn in kVA

3.the gross power

4.the output power available at the shaft

## Question: `The ratio of starting torque to full-load torque is least in case of`

1.series motors

2.shunt motor

3.compound motors

4.none of the above

## Question: `The speed of a D.C. motor can be varied by varying`

1.field current

2.applied voltage

3.resistance in series with armature

4.any of the above

## Question: `The speed of a D.C. series motor is`

1.proportional to the armature current

2.proportional to the square of the armature current

3.proportional to field current

4.inversely proportional to the armature current

## Question: `The speed of a D.C. shunt motor more than its full-load speed can be obtained by`

1.decreasing the field current

2.increasing the field current

3.decreasing the armature current

4.increasing the armature current

## Question: `The starting resistance of a D.C. motor is generally`

1.low

2.around 500 Q

3.1000 Q

4.infinitely large

## Question: `The type of D.C. motor used for shears and punches is`

1.shunt motor

2.series motor

3.differential compoutid D.C. motor

4.cumulative compound D.C. motor

## Question: `These days D.C. motors are widely used in`

1.pumping sets

2.air compressors

3.electric traction

4.machine shops

## Question: `To get the speed of D.Cmotor below the normal without wastage of electrical energy is used.`

1.Ward Leonard control

2.rheostatic control

3.any of the above method

4.none of the above method

## Question: `What will happen if the back e.m.f. of a D.C. motor vanishes suddenly?`

1.The motor will stop

2.The motor will continue to run

3.The armature may burn

4.The motor will run noisy

## Question: `When two D.C. series motors are connected in parallelthe resultant speed is`

1.more than the normal speed

2.loss than the normal speed

3.normal speed

4.zero

## Question: `Which D.C. motor is generally preferred for cranes and hoists ?`

1.Series motor

2.Shunt motor

3.Cumulatively compounded motor

4.Differentially compounded motor

## Question: `Which D.C. motor is preferred for elevators ?`

1.Shunt motor

2.Series motor

3.Differential compound motor

4.Cumulative compound motor

## Question: `Which D.C. motor will be preferred for machine tools ?`

1.Series motor

2.Shunt motor

3.Cumulative compound motor

4.Differential compound motor

## Question: `Which D.C. motor will be suitable alongwith flywheel for intermittent light and heavy loads?`

1.Series motor

2.Shunt motor

3.Cumulatively compounded motor

4.Differentially compounded motor

## Question: `Which of the following application requires high starting torque ?`

1.Lathe machine

2.Centrifugal pump

3.Locomotive

4.Air blower

## Question: `Which of the following load normally needs starting torque more than the rated torque?`

1.Blowers

2.Conveyors

3.Air compressors

4.Centrifugal pumps

## Question: `Which of the following motor is preferred for operation in highly explosive atmosphere ?`

1.Series motor

2.Shunt motor

3.Air motor

4.Battery operated motor

## More MCQS

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