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- Question
A dc separately excited motor has constant field current. The armature is fed from a single phase supply through a full converter. When a = 0, speed is 500 rpm. If a = 45°, the speed is likely to be
Options- A. about 350 rpm
- B. about 250 rpm
- C. about 175 rpm
- D. about 125 rpm
- Correct Answer
- about 125 rpm
ExplanationAverage output voltage ? cos a and therefore reduced to 0.707 of the value for a = 0. Speed is nearly proportional to voltage.
More questions
- 1. Frequency range for satellite communication is
Options- A. 1 kHz to 100 kHz
- B. 100 kHz to 10 MHz
- C. 10 MHz to 100 MHz
- D. 1 GHz to 30 GHz Discuss
Correct Answer: 1 GHz to 30 GHz
- 2. To prevent a DC return between source and load, it is necessary to use
Options- A. resistor between source and load
- B. inductor between source and load
- C. capacitor between source and load
- D. either (a) or (b) Discuss
Correct Answer: capacitor between source and load
Explanation:
Capacitor offers infinite impedance to DC.- 3. Dielectric constant of transformer oil is about
Options- A. 1
- B. 4
- C. 10
- D. 20 Discuss
Correct Answer: 4
- 4. Which one of the following can be used for amplification of microwave energy?
Options- A. TWT
- B. Magnetron
- C. Reflex klystron
- D. Gunn diode Discuss
Correct Answer: TWT
- 5. Which of the following is wrong for a magic used to tee?
Options- A. E and H arms are decoupled
- B. coplanar arms are coupled
- C. all ports are perfectly matched
- D. A signal into coplanar arm splits equally between E and H arms Discuss
Correct Answer: coplanar arms are coupled
Explanation:
Coplanar arms are decoupled.- 6. A UJT exhibits negative resistance characteristics when
Options- A. Current is less than valley current
- B. Current is less than peak current
- C. Current is more than peak current but less than valley current
- D. None of the above Discuss
Correct Answer: Current is more than peak current but less than valley current
- 7. The signal defined by the equations f(t) = 0 for t < 0, f(t) = E for 0 ? t ? a and f(t) = 0 for t > a is
Options- A. a step function
- B. a pulse function
- C. a shifted step function originating at t = a
- D. none of the above Discuss
Correct Answer: a pulse function
Explanation:
It is a pulse lasting for t = a.- 8. Which of the following real variable names is not valid in Fortran?
Options- A. BETA
- B. ALPHA
- C. A
- D. AB * 2 Discuss
Correct Answer: AB * 2
Explanation:
Operator is not allowed.- 9. TE10 mode of propagation of electromagnetic energy in waveguides can be thought of as
Options- A. three TEM waves travelling along length of wave-guide
- B. One TEM wave travelling along length of wave guide and one TEM wave propagation in the transverse plane
- C. One TEM wave travelling along the length of wave guide and two TEM waves
- D. none of the above Discuss
Correct Answer: One TEM wave travelling along the length of wave guide and two TEM waves
- 10. In sinusoidal PWM for inverters the width of different pulses are not the same.
Options- A. True
- B. False Discuss
Correct Answer: True
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