Induction motor 1-4

1) An induction motor having 8 poles runs at 727.5 rpm. if the supply frequency is 50Hz, The emf in the rotor will have a frequency of
a)    1.5Hz
b)    2.5Hz
c)    48.5Hz
d)    51.5Hz

2) The crawling in the induction motor is caused by
a)    improper design of stator lamination
b)    low voltage supply
c)    high loads   
d)    harmonics developed in the motor  

3). Which of the following statement is correct ? In an induction motor if the air gap is increased then
a)    its speed will reduce    
b)    its speed will increase
c)    its power factor will reduce
d)    its efficiency will improve

4). The supply voltage to an induction motor is reduced by 10%. By what percentage , approximately , will the maximum torque decreases?
a)    40%   
b)    20%
c)    10%
d)    5%

5). When applied rated voltage per phase is reduced to one half , the starting torque of three phase squirrel cage induction motor become
a)    1/2 of the initial value  
b)    1/4 of the initial value
c)    wice the initial value
d)    4 Times the initial value

6). The rotor slots are slightly skewed in squirrel cage induction motor to
a)    Provide ease of fabrication
b)    reduce the magnetic hum and locking tendency of rotor
c)    increasing the strengths of rotor bars
d)    economic on the copper to be used

8). what is the frequency of rotor current of 50 HZ induction motor operating at 4% slip ?
a)    50 Hz  
b)    2.5 Hz
c)    1 Hz
d)    2 Hz

8).What kind of planning controls being exercised by the free market economies?
a)    Direct control
b)    Indirect Control
c)    Physical Control
d)    Other Control

9). A 3-phase 6 pole 50 Hz induction motor is running at 5% slip , What is the speed of the motor ?
a)    1000 rpm
b)    9000 rpm
c)    950 rpm    
d)    850 rpm

10). Which of the following is/are not a self starting motor ?
a)    3-Phase induction motor
b)    1-Phase induction motor
c)    Both 1 and 2
d)    Non of the above :p>