Handa Mcqs Chapter 18 DC Motor (MCQS 01 TO 10)

01) The full load current of a 20 HP 500 V dc motor will be closer to 

• a)    100A
• b)    60A
• c)    35A
• d)    15A

 Explanation       Given At The End

02) The speed of a dc motor may be varied by varying

• a)    field current 
• b)    applied voltage
• c)    resistance in series with armature
• d)    any of the above

  Explanation       Given At The End

03) In dc motors, the conditions for maximum power is 

• a)    supply voltage = 1/2-time back emf
• b)    supply voltage = Square root 2-time back emf
• c)    Back emf = 2-time supply voltage
• d)    Back emf = 1/2-time supply voltage

  Explanation       Given At The End

04) If conditions for maximum power for a dc motor are established, the efficiency of the motor will be

• a)    100%
• b)    90 to 96%
• c)    81% 
• d)    less than 50%

  Explanation       Given At The End

05) A 200V dc machine has an armature resistance of 0.5 ohm If the full armature current is 30A, the induced emf when the machine act as (i) generator (ii) motor, will be 

• a)    170V,230V 
• b)    175V,225V
• c)    185V,215V
• d)    120V,210V

  Explanation       Given At The End

06) The speed of a dc motor is 

• a)    always constant
• b)    directly proportional to back emf
• c)    directly proportional to flux
• d)    inversely proportional to the product of back emf and flux

  Explanation       Given At The End

07) The ratio of starting torque to fully load torque is least in case of 

• a)    shunt motor
• b)    series motor
• c)    compound motors

  Explanation       Given At The End

08) which of the following is not necessarily the advantage of dc motor over ac motors?

• a)    High starting torque
• b)    wide speed range
• c)    better speed control
• d)    low cost

  Explanation       Given At The End

09) which motor will have least percentage increase of input current for the same percentage increase in torque?

• a)    series motor
• b)    shunt motor
• c)    separately excited motor
• d)    cumulatively compound motors

  Explanation       Given At The End

10) The mechanical power developed by a dc motor is maximum when the ratio of back emf/applied voltage is 

• a)       1.0
• b)      3.0
• c)       0.5
• d)      0.7

  Explanation       Given At The End

All Above MCQs Solution is Explained in this Video.