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Question
If
is the Laplace transform of
f
(
t
) then
f
(0
+
) is
Options
A. 0
B.
C. 27
D. ?
Correct Answer
27
Explanation
.
More questions
1. In a parallel inverter the turn off time
t
q
of thyristor and values of commutating elements L and C are related as
Options
A.
t
q
=
p
LC
B.
t
q
=
LC
C.
t
q
=
LC
D.
t
q
=
LC
Show Answer
Scratch Pad
Discuss
Correct Answer:
t
q
=
LC
2. APPLE was into orbit on 19 th June 1981 by European Space Agency (ESA) from
Options
A. Cape Canaveral in Florida
B. Kourou in French Guyana
C. Canarvon in Western Australia
D. Bangalore in South India
Show Answer
Scratch Pad
Discuss
Correct Answer: Kourou in French Guyana
3. In the below figure, the average value of load current is 15 A. The load is highly inductive. The peak value of thyristor current is
Options
A. 15 A
B. 15
2
A
C.
D. 30 A
Show Answer
Scratch Pad
Discuss
Correct Answer: 15 A
Explanation:
Because of highly inductive load, output current is nearly constant.
4. On load tap changer using thyristors can have a maximum of two taps.
Options
A. True
B. False
Show Answer
Scratch Pad
Discuss
Correct Answer: False
Explanation:
Any number of taps are possible.
5. A single phase half wave regulator uses
Options
A. 2 diodes and 2 thyristors
B. 2 thyristors
C. 1 diode and 1 thyristor
D. 2 diodes
Show Answer
Scratch Pad
Discuss
Correct Answer: 1 diode and 1 thyristor
Explanation:
Regulation is possible only in positive half cycle.
6. The temperature coefficient of resistivity of semiconductors is
Options
A. positive
B. negative
C. may be positive or negative
D. very low
Show Answer
Scratch Pad
Discuss
Correct Answer: negative
Explanation:
Resistance of semiconductors decreases with increase in temperature.
7. When a communication satellite passes into Earth's shadow, its temperature drops to about __________ ° K.
Options
A. 273
B. 243
C. 170
D. 123
Show Answer
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Discuss
Correct Answer: 123
8. A rectifier is fed by a transformer. The rms voltage and current at secondary of transformer are V
s
and I
s
. Output dc power is V
dc
I
dc
and output ac power is (V
rms
) (I
rms
), Transformer utilisation factor TUF is
Options
A.
B.
C.
D.
Show Answer
Scratch Pad
Discuss
Correct Answer:
9. In the case of a 70-MHz IF carrier for a transponder bandwidth of 36 MHz, energy must lie between MHz.
Options
A. 34 and 106
B. 52 and 88
C. 106 and 142
D. 34 and 142
Show Answer
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Discuss
Correct Answer: 52 and 88
10. In a 3 phase semiconverter, the dc output voltage for a certain firing angle is 50% of the maximum possible value. The firing angle is
Options
A. 30°
B. 60°
C. 90°
D. 120°
Show Answer
Scratch Pad
Discuss
Correct Answer: 90°
Explanation:
V
dc
? (1 + cos
a
). Maximum possible output voltage occurs when
a
= 0.
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