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- Question
A dc separately excited motor has a constant field current. The armature is fed from a single phase supply through a semi-converter. When a = 0, speed is 600 rpm. If a = 90°, the speed is likely to be
Options- A. about 300 rpm
- B. about 150 rpm
- C. about 75 rpm
- D. about zero
- Correct Answer
- about 300 rpm
ExplanationAverage output voltage is reduced to 50% if a = 90°. Hence speed is also reduced to 50%.
More questions
- 1. In which of these is reverse recovery time nearly zero?
Options- A. Zener diode
- B. Tunnel diode
- C. Schottky diode
- D. PIN diode Discuss
Correct Answer: Schottky diode
Explanation:
In schottky diode there is no charge storage and hence almost zero reverse recovery time.- 2. The number of leads in a DIAC are
Options- A. 2
- B. 3
- C. 4
- D. 6 Discuss
Correct Answer: 2
- 3. A dc chopper V = 500 V feeds an electric fraction dc series motor. The chopping frequency is 400 Hz. The series inductance required to limit the maximum current swing to 10 A is
Options- A. 20 mH
- B. about 31 mH
- C. about 51 mH
- D. about 92 mH Discuss
Correct Answer: about 31 mH
Explanation:
.
- 4. The capacitance of a capacitor is not affected by
Options- A. area of plates
- B. thickness of plates
- C. ?r
- D. distance between plates Discuss
Correct Answer: thickness of plates
Explanation:
Capacitance depends on area, distance and ?r but not on thickness of plates.- 5. In a semi converter feeding a resistive load
Options- A. the waveshapes of output voltage and output current are exactly similar
- B. the waveshapes of output voltage and output current can not be similar
- C. the waveshapes of output voltage and output current are similar only for low values of firing angle
- D. the waveshapes of output voltage and output current may be similar or dissimilar Discuss
Correct Answer: the waveshapes of output voltage and output current are exactly similar
- 6. The field pattern of a solenoid is similar to that of bar magnet.
Options- A. True
- B. False Discuss
Correct Answer: True
- 7. Match the following:
List I (Logic family) List II (Characteristic of logic family) A. TTL 1. Maximum power Consumption B. ECL 2. Highest Packing Density C. NMOS 3. Least Power Consumption D. CMOS 4. Saturated Logic
Options- A. A-1, B-4, C-2, D-3
- B. A-1, B-4, C-3, D-2
- C. A-4, B-1, C-2, D-3
- D. A-4, B-1, C-3, D-2 Discuss
Correct Answer: A-4, B-1, C-2, D-3
- 8. An electron shell corresponding to principal quantum number n can contain a maximum of
Options- A. n2 electrons
- B. 2n2 electrons
- C. 2n electron
- D. n3 electron Discuss
Correct Answer: 2n2 electrons
Explanation:
The electron shell corresponding to the principal quantum number can contain no more than 2n2 electrons.- 9. The diagram to show distance time history of electrons in klystron amplifier is called
Options- A. apple gate diagram
- B. asynchronous diagram
- C. bunching diagram
- D. velocity modulation diagram Discuss
Correct Answer: apple gate diagram
Explanation:
Applegate diagram is distance time plot.- 10. Spontaneous magnetisation is characteristic of ferromagnetic materials.
Options- A. True
- B. False Discuss
Correct Answer: True
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