Question 1

The armature voltage control of D.C. motor provides

Accepted Answer

A) constant torque drive 
B) constant voltage drive 
C) constant current drive 
D) none of the above 
A) constant torque drive 
B) constant voltage drive 
C) constant current drive 
D) none of the above A

Question 2

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

Accepted Answer

A) remain unchanged 
B) reduce to one-fourth value 
C) increase four folds 
D) be doubled 
A) remain unchanged 
B) reduce to one-fourth value 
C) increase four folds 
D) be doubled A

Question 3

Three point starter can be used for

Accepted Answer

A) series motor only 
B) shunt motor only 
C) compound motor only 
D) both shunt and compound motor 
A) series motor only 
B) shunt motor only 
C) compound motor only 
D) both shunt and compound motor D

Question 4

The speed of a D.C. shunt motor can be increased by

Accepted Answer

A) increasing the resistance in armature circuit 
B) increasing the resistance in field circuit 
C) reducing the resistance in the field circuit 
D) reducing the resistance in the armature circuit 
A) increasing the resistance in armature circuit 
B) increasing the resistance in field circuit 
C) reducing the resistance in the field circuit 
D) reducing the resistance in the armature circuit

Question 5

In a differentially compounded D.C. motor, if shunt field suddenly opens

Accepted Answer

A) the motor will first stop and then run in opposite direction as series motor 
B) the motor will work as series motor and run at slow speed in the same direction 
C) the motor will work as series motor and run at high speed in the same direction 
D) the motor will not work and come to stop 
A) the motor will first stop and then run in opposite direction as series motor 
B) the motor will work as series motor and run at slow speed in the same direction 
C) the motor will work as series motor and run at high speed in the same direction 
D) the motor will not work and come to stop

Question 6

If I2 be the armature current, then speed of a D.C. shunt motor is

Accepted Answer

A) independent of Ia 
B) proportional to la 
C) varies as (Ia) 
D) varies as la 
A) independent of Ia 
B) proportional to la 
C) varies as (Ia) 
D) varies as la

Question 7

Which motor has the poorest speed control?

Accepted Answer

A) Differentially compounded motor 
B) Cumulatively compounded motor 
C) Shunt motor 
D) Series motor 
A) Differentially compounded motor 
B) Cumulatively compounded motor 
C) Shunt motor 
D) Series motor

Question 8

For a D.C. shunt motor if the excitation is changed

Accepted Answer

A) torque will remain constant 
B) torque will change but power will remain constant 
C) torque and power both will change 
D) torque, power and speed, all will change 
A) torque will remain constant 
B) torque will change but power will remain constant 
C) torque and power both will change 
D) torque, power and speed, all will change

Question 9

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

Accepted Answer

A) a resistance is connected in series with armature 
B) a resistance is connected parallel to the armature 
C) armature is temporarily open circuited 
D) a high value resistor is connected across the field winding 
A) a resistance is connected in series with armature 
B) a resistance is connected parallel to the armature 
C) armature is temporarily open circuited 
D) a high value resistor is connected across the field winding

Question 10

Usually wide and sensitive speed control is desired in case of

Accepted Answer

A) centrifugal pumps 
B) elevators 
C) steel rolling mills 
D) colliery winders 
A) centrifugal pumps 
B) elevators 
C) steel rolling mills 
D) colliery winders

Question 11

At the instant of starting when a D.C. motor is put on supply, it behaves like

Accepted Answer

A) a highly resistive circuit 
B) a low resistance circuit 
C) a capacitive circuit 
D) none of the above 
A) a highly resistive circuit 
B) a low resistance circuit 
C) a capacitive circuit 
D) none of the above

Question 12

Following motor is used where high starting torque and wide speed range control is required.

Accepted Answer

A) Single phase capacitor start 
B) Induction motor 
C) Synchronous motor 
D) D.C. motor 
A) Single phase capacitor start 
B) Induction motor 
C) Synchronous motor 
D) D.C. motor

Question 13

In D.C. machines the residual magnetism is of the order of

Accepted Answer

A) 2 to 3 per cent 
B) 10 to 15 per cent 
C) 20 to 25 per cent 
D) 50 to 75 per cent 
A) 2 to 3 per cent 
B) 10 to 15 per cent 
C) 20 to 25 per cent 
D) 50 to 75 per cent

Question 14

As -the load is increased the speed of D.C. shunt motor will

Accepted Answer

A) reduce slightly 
B) increase slightly 
C) increase proportionately 
D) remains unchanged 
A) reduce slightly 
B) increase slightly 
C) increase proportionately 
D) remains unchanged

Question 15

Which D.C. motor is generally preferred for cranes and hoists ?

Accepted Answer

A) Series motor 
B) Shunt motor 
C) Cumulatively compounded motor 
D) Differentially compounded motor 
A) Series motor 
B) Shunt motor 
C) Cumulatively compounded motor 
D) Differentially compounded motor

Question 16

Which of the following motor has the poorest speed regulation ?

Accepted Answer

A) Shunt motor 
B) Series motor 
C) Differential compound motor 
D) Cumulative compound motor 
A) Shunt motor 
B) Series motor 
C) Differential compound motor 
D) Cumulative compound motor

Question 17

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

Accepted Answer

A) Voltage control method 
B) Field control method 
C) Armature control method 
D) All above methods 
A) Voltage control method 
B) Field control method 
C) Armature control method 
D) All above methods

Question 18

The speed of a D.C. motor can be varied by varying

Accepted Answer

A) field current 
B) applied voltage 
C) resistance in series with armature 
D) any of the above 
A) field current 
B) applied voltage 
C) resistance in series with armature 
D) any of the above

Question 19

Speed control by Ward Leonard method gives uniform speed variation

Accepted Answer

A) in one direction 
B) in both directions 
C) below normal speed only 
D) above normal speed only. 
A) in one direction 
B) in both directions 
C) below normal speed only 
D) above normal speed only.

Question 20

The speed of a motor falls from 1100 r.p.m. at no-load to 1050 r.p.m. at rated load. The speed regulation of the motor is

Accepted Answer

A) 2.36% 
B) 4.76% 
C) 6.77% 
D) 8.84% 
A) 2.36% 
B) 4.76% 
C) 6.77% 
D) 8.84%

The armature voltage control of D.C. motor provides

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

Three point starter can be used for

The speed of a D.C. shunt motor can be increased by

In a differentially compounded D.C. motor, if shunt field suddenly opens

If I2 be the armature current, then speed of a D.C. shunt motor is

Which motor has the poorest speed control?

For a D.C. shunt motor if the excitation is changed

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

Usually wide and sensitive speed control is desired in case of

At the instant of starting when a D.C. motor is put on supply, it behaves like

Following motor is used where high starting torque and wide speed range control is required.

In D.C. machines the residual magnetism is of the order of

As -the load is increased the speed of D.C. shunt motor will

Which D.C. motor is generally preferred for cranes and hoists ?

Which of the following motor has the poorest speed regulation ?

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

The speed of a D.C. motor can be varied by varying

Speed control by Ward Leonard method gives uniform speed variation

The speed of a motor falls from 1100 r.p.m. at no-load to 1050 r.p.m. at rated load. The speed regulation of the motor is

D.C. Motors and Their Applications

D.C. Motors

D.C. Motors and Generators

D.C. Generator and Motor Efficiency, Testing and Braking Techniques

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Exam 3: D.C. Motors and Speed Control

The armature voltage control of D.C. motor provides

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

Three point starter can be used for

The speed of a D.C. shunt motor can be increased by

In a differentially compounded D.C. motor, if shunt field suddenly opens

If I2 be the armature current, then speed of a D.C. shunt motor is

Which motor has the poorest speed control?

For a D.C. shunt motor if the excitation is changed

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

Usually wide and sensitive speed control is desired in case of

At the instant of starting when a D.C. motor is put on supply, it behaves like

Following motor is used where high starting torque and wide speed range control is required.

In D.C. machines the residual magnetism is of the order of

As -the load is increased the speed of D.C. shunt motor will

Which D.C. motor is generally preferred for cranes and hoists ?

Which of the following motor has the poorest speed regulation ?

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

The speed of a D.C. motor can be varied by varying

Speed control by Ward Leonard method gives uniform speed variation

The speed of a motor falls from 1100 r.p.m. at no-load to 1050 r.p.m. at rated load. The speed regulation of the motor is

D.C. Motors and Their Applications

D.C. Motors

D.C. Motors and Generators

D.C. Generator and Motor Efficiency, Testing and Braking Techniques

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