Electrical Engineering Mcqs Practice Test

Question 1

In induction motor, percentage slip depends on__________?

Accepted Answer

C. copper losses in motor

Question 2

When /?2 is the rotor resistance, .X2 the rotor reactance at supply frequency and s the slip, then the condition for maximum torque under running conditions will be_____________?

Accepted Answer

C. R2 = sX2

Question 3

In case of a double cage induction motor, the inner cage has__________?

Accepted Answer

A. high inductance arid low resistance

Question 4

In an induction motor if air-gap is increased__________?

Accepted Answer

A. the power factor will be low

Question 5

The torque developed by a 3-phase induction motor least depends on__________?

Accepted Answer

D. shaft diameter

Question 6

Which motor is preferred for use in mines where explosive gases exist ?

Accepted Answer

A. Air motor

Question 7

Lubricant used for ball bearing is usually___________?

Accepted Answer

B. grease

Question 8

The circle diagram for an induction motor cannot be used to determine____________?

Accepted Answer

A. efficiency

Question 9

Blocked rotor test on induction motors is used to find out?

Accepted Answer

D. all of the above

Question 10

The complete circle diagram of induetion motor can be drawn with the help of data found from__________?

Accepted Answer

D. all of the above

Question 11

In the squirrel-cage induction motor the rotor slots are usually given slight skew__________?

Accepted Answer

A. to reduce the magnetic hum and locking tendency of the rotor

Question 12

The torque of a rotor in an induction motor under running condition is maximum__________?

Accepted Answer

C. at the value of the slip which makes rotor reactance per phase equal to the resistance per phase

Question 13

What will happen if the relative speed between the rotating flux of stator and rotor of the induction motor is zero ?

Accepted Answer

B. The rotor will not run

Question 14

The stating torque of the slip ring induction motor can be increased by adding__________?

Accepted Answer

B. external resistance to the rotor

Question 15

A 500 kW, 3-phase, 440 volts, 50 Hz, A.C. induction motor has a speed of 960 r.p.m. on full load. The machine has 6 poles. The slip of the machine will be__________?

Accepted Answer

D. 0.04

Question 16

The power scale of circle diagram of an induction motor can be found from__________?

Accepted Answer

C. short-circuit test only

Question 17

A change of 4% of supply voltage to an induction motor will produce a change of approximately ________?

Accepted Answer

D. 16% in the rotor torque

Question 18

The shape of the torque/slip curve of induction motor is__________?

Accepted Answer

C. rectangular parabola

Question 19

The vafcie of transformation ratio of an induction motor can be found by__________?

Accepted Answer

B. short-circuit test only

Question 20

In a three-phase induction motor__________?

Accepted Answer

B. power factor at starting is low as compared to that while running