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- Question
In fibre optics the use is made of thin glass fibres for efficient transmission of light.
Options- A. True
- B. False
- Correct Answer
- True
- 1. A 3 phase induction motor is controlled by voltage and frequency control such that the ratio V/f is constant. At 50 Hz, the starting torque is 100 N-m. At 25 Hz, the starting torque
Options- A. will be less than 100 N-m
- B. will be more than 100 N-m
- C. may be more or less than 100 N-m depending on motor parameters
- D. very small Discuss
- 2. The phenomenon of overlap in converter operation due to
Options- A. source resistance
- B. source inductance
- C. both source resistance and source inductance
- D. high value of firing angle Discuss
- 3. As the frequency is increased, the charging MVAR in a cable
Options- A. decreases
- B. increases
- C. remain the same
- D. decreases or remains the scheme Discuss
- 4. A step down cycloconverter has an input frequency f. If it uses natural commutation, the output frequency
Options- A. must be a sub-multiple of input frequency
- B. can be any frequency
- C. must be an even sub-multiple of input frequency
- D. must be an odd sub-multiple of input frequency Discuss
- 5. If
, the terms in f(t) will have
Options- A. e-t and e-2t
- B. et and e2t
- C. te-t and te-2t
- D. none of the above Discuss
- 6. Out of modes TE20 and TE30 of propagation of electromagnetic engery
Options- A. both have the same cutoff frequency
- B. TE20 has lower cut off frequency as compared to TE30
- C. TE30 has lower cutoff frequency as compared to TE20
- D. either (a) or (c) Discuss
- 7. Two function g1(t) and g2(t) with correlation of 6 has average power of 4 and 5 respectively. The power of g1(t) + g2(t) is
Options- A. 9
- B. 21
- C. 3
- D. 15 Discuss
- 8. An SUS is
Options- A. exactly similar to SCR but with higher rating
- B. similar to UJT
- C. PUT and avalanche diode connected in anti parallel
- D. SCR and avalanche diode connected in parallel Discuss
- 9. The static equalisation circuit for thyristors connected in series is
Options- A. one resistor in series with each thyristor
- B. one resistor in parallel with each thyristor
- C. one resistor and one capacitor in parallel with each thyristor
- D. none of the above Discuss
- 10. The cut in voltages for germanium and silicon diodes respectively as
Options- A. 0.3 V and 0.7 V
- B. 0.7 V and 0.3 V
- C. 0.6 V and 0.9 V
- D. 0.5 V and 0.7 V Discuss
More questions
Correct Answer: will be more than 100 N-m
Correct Answer: source inductance
Explanation:
Source inductance delays turn off and hence causes overlap.
Correct Answer: increases
Explanation:
Charging current and MVAR are proportional to frequency.
Correct Answer: must be a sub-multiple of input frequency
Correct Answer: e-t and e-2t
Explanation:
(s + 1) term will give e-t and (s + 2) term will give e-2t .
Correct Answer: TE20 has lower cut off frequency as compared to TE30
Correct Answer: 21
Explanation:
Power of two correlated signal is P = P1 + P2 +2R1, 2(t).
Correct Answer: PUT and avalanche diode connected in anti parallel
Correct Answer: one resistor in parallel with each thyristor
Correct Answer: 0.3 V and 0.7 V
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