# Speed Control of Direct Current Motor MCQ

1. The advantage of the double squirrel cage induction motor over a single cage rotor is that it’s _______

A. Efficiency is higher

B. Power factor is higher

C. Slip is larger

D. Starting current is lower

2. A 16-pole, 3-phase, 60 Hz induction motor is operating at a speed of 150 rpm. The frequency of the rotor current of the motor in Hz is __________

A. 20

B. 40

C. 30

D. 10

3. Calculate the amplitude of the sinusoidal waveform z(t)=715sin(165πt+2π÷468).

A. 710

B. 715

C. 716

D. 718

4. R.M.S value of the sinusoidal waveform V=48sin(6.5πt+89π÷46.8).

A. 33.94 V

B. 33.56 V

C. 33.12 V

D. 33.78 V

5. The short circuit test on a 3-φ induction motor is conducted at a rotor speed of _______

A. Zero

B. < Ns

C. > Ns

D. Ns

6. If induction motor air gap power is 10 KW and mechanically developed power is 8 KW, then rotor ohmic loss will be _________ KW.

A. 1

B. 2

C. 3

D. 4

7. A 3-phase induction machine draws active power P and reactive power Q from the grid. If it is operated as a generator, then P and Q will be _________

A. Positive and Negative

B. Negative and Positive

C. Positive and Positive

D. Negative and Negative

8. The slope of the V-I curve is 39.1°. Calculate the value of resistance. Assume the relationship between voltage and current is a straight line.

A. .81 Ω

B. .36 Ω

C. .75 Ω

D. .84 Ω

9. If induction motor air gap power is 48 KW and gross developed power is 28 KW, then rotor ohmic loss will be _________ KW.

A. 10

B. 20

C. 30

D. 40

10. The power factor of a squirrel cage induction motor is ___________

A. Low at light load only

B. Low at heavy loads only

C. Low at the light and heavy loads both

D. Low at rate load only

11. Calculate the active power in a .154 H inductor.

A. 22 W

B. 14 W

C. 45 W

D. 0 W

12. Calculate the time period of the waveform z(t)=24sin(πt+π÷4)+4sin(2πt+π÷6).

A. 2 sec

B. 3 sec

C. 4 sec

D. 1 sec

13. Calculate the total heat dissipated in a resistor of 50 Ω when 1.4 A current flows through it.

A. 98 W

B. 92 W

C. 91 W

D. 93 W

14. Calculate mark to space ratio if the system is on for 26.3 sec and off for 24.2 sec.

A. 1.086

B. 1.042

C. 1.214

D. 1.876

15. A particular current is made up of two components: a 10 A and a sine wave of peak value 14.14 A. The average value of current is _________

A. Zero

B. 24.14 A

C. 10 A

D. 14.14 A

16. A 38-pole, 3-phase, 80 Hz induction motor is operating at a speed of 12 rpm. The frequency of the rotor current of the motor in Hz is __________

A. 75.2

B. 76.1

C. 79.2

D. 79.6

17. Calculate the phase angle of the sinusoidal waveform i(t)=sin(.6πt+π÷.88).

A. 100π÷88

B. 100π÷8

C. 100π÷8

D. π÷88

18. Calculate the moment of inertia of the satellite having a mass of 79 kg and diameter of 83 cm.

A. 13.65 kgm^{2}

B. 13.60 kgm^{2}

C. 12.67 kgm^{2}

D. 13.82 kgm^{2}

19. A particular voltage is made up of two components: a 5 A and a cosine wave of peak value 7.8 A. The average value of voltage is _________

A. Zero

B. 35.14 A

C. 78 A

D. 5 A

20. Armature reaction is demagnetizing in nature due to a purely capacitive load in the synchronous generator.

A. True

B. False