1). An induction motor has a rotor resistance of 0.002Ω/phase. If the resistance increased to 0.004Ω/phase then the maximum torque will

a)
Reduced to half

b)
increased by 100%

c)
Increased by 200%

d)
Remain unaltered

2). The power factor of squirrel cage induction motor is

a)
low at light loads only

b)
low at heavy load only

c)
Both a and b

d)
Low at rated load only

3). Cogging of induction motor occurs at

a)
High voltage and when stator and rotor poles are equal

b)
Low voltage and when stator and rotor poles are equal

c)
High voltage and when stator and rotor poles are not equal

d)
Low voltage and when stator and rotor poles are not equal

4). Cogging and crawling are phenomena associated with

a)
cage induction machines and they are essentially the same

b)
the former during starting and the latter at a fraction of its rated speed

c)
the former at a fraction of its rated speed and the latter during starting

d)
any of the above

5).Cogging in the induction motor occurs when

a)
number of stator teeth - number of rotor teeth = odd number

b)
number of stator teeth - number of rotor teeth = even number

c)
number of stator teeth - number of rotor teeth = 0

d)
number of stator teeth - number of rotor teeth = negative number

6). A 4 pole 50Hz induction motor is running at 1470 rmp. Find the speed of stator magnetic field with respect to rotor?

a)
1470 rpm

b)
1500 rpm

c)
30 rpm

d)
zero

7).No load test of 3-phase induction motor gives which of the following ?

a)
constant loss

b)
variable loss

c)
both a and b

d)
non of the above

8). An induction motor is , in general analogous to

a)
Two winding transformer with secondary slot circuited

b)
Two winding transformer with secondary open circuited

c)
Auto transformer

d)
non of the above

9). A 3-phase slip ring induction motor is wound for 4 poles on stator and 6 poles on the rotor. when 3-phase balanced voltage source at 50Hz is applied, it will run at

a)
1500 rpm

b)
1000 rpm

c)
zero speed

d)
750 rpm

10). A voltmeter gives 120 oscillations per minute when connected to rotor of an induction motor. The frequency is 50Hz. The slip of the motor is

a)
2%

b)
5%

c)
4%

d)
25%