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B.Tech. Foundation Test (Electronics) / page 1
NATIONAL UNIVERSITY OF SINGAPORE
B.Tech. Foundation Test – Electronics
Time Allowed: 2 Hours
September 2007
Answer all twenty multiple choice questions. Put down your name and answer below.
Question
Name:
Answer (Shade one of the boxes A or B or C or D)
1
A
B
C
D
2
A
B
C
D
3
A
B
C
D
4
A
B
C
D
5
A
B
C
D
6
A
B
C
D
7
A
B
C
D
8
A
B
C
D
9
A
B
C
D
10
A
B
C
D
11
A
B
C
D
12
A
B
C
D
13
A
B
C
D
14
A
B
C
D
15
A
B
C
D
16
A
B
C
D
17
A
B
C
D
18
A
B
C
D
19
A
B
C
D
20
A
B
C
D
Mark:
B.Tech. Foundation Test (Electronics) / page 2
Q.1
Which of the following is correct?
A – The source is a current source.
B – The current may flow upward or downward depending on i.
C – Both A and B are wrong.
D – Both A and B are correct.
Q.2
The device is giving power. Which of the following is correct?
A – v and i have the same sign.
B – v and i have the opposite signs.
C – v is positive.
D – i is positive.
Q.3
What is the phase of the complex sinusoid  6  j 7e  j 8t ?
A – Between  90 0 and 90 0 .
B – Between  90 0 and  180 0 .
C – Between 90 0 and 180 0 .
D – None of the above.
Q.4
What is the frequency of the complex sinusoid  6  j 7e  j 8t ?
A – Equal to 8 Hz .
B – Equal to  8 Hz .
C – Equal to 8 rad sec .
D – None of the above.
Q.5
What is the power of  6  j 7 e  j 8t  9 sin 11t ?


 
A – Equal to 6 2  9 2 2 .
B – Equal to 6 2  7 2  9 2 2 .
C – Not defined as the signal is complex.
D – None of the above.

Q.6

What is the rms value of 4 cos5t   6 sin
 7t  ?
A – Equal to 0.54 2   0.56 2  .
B – Equal to 4  6 .
C – Not defined as the signal is not periodic.
D – None of the above.
B.Tech. Foundation Test (Electronics) / page 3
Q.7
A TV signal booster has a gain of 20 dB. Which of the following is correct?
A – The output to input power ratio is 100.
B – The output to input voltage ratio is 10.
C – Both A and B are wrong.
D – Both A and B are correct.
Q.8
A filter has a frequency response of 4  j6 f . What is the output if the input is
3  5 cos2 7t  ?
A – Equal to 4  j6 f 3  5 cos2 7t .
B – Equal to 43 j 6 f 5 cos2 7t  .


C – Equal to 12  5 4 2  42 2 cos 2 7t  tan 1 42 4 .
D – None of the above.
Q.9
A 3 F capacitor is in series with a 4 H inductor. The impedance at 5 rad/sec is
A – Equal to j15  j 20 .
B – Equal to j 20  j 15 .
C – Equal to j 5 .
D – None of the above.
Q.10
A 3 F capacitor is in series with a 4 H inductor. Which of the following is correct?
A – The combined impedance is always positive.
B – The combined impedance is always negative.
C – The combined impedance may be 0.
D – None of the above.
Q.11
In a Norton equivalent circuit, the current source is 3A and the resistance is 7 .
What is the open circuit voltage?
A – Equal to 21 V.
B – Equal to 5 V.
C – Undefined as there is no voltage source.
D – None of the above.
Q.12
In a Norton equivalent circuit, the current source is 3A and the resistance is 7 .
What is the maximum power that can be drawn?
A – Equal to 21 W.
B – Equal to 10.5 W.
2
C – Equal to 71.5 W.
D – None of the above.
B.Tech. Foundation Test (Electronics) / page 4
Q.13
The voltage current relationship of a 2-terminal circuit is v  10  5i .
What is the internal resistance in the corresponding equivalent Thevenin circuit?
A – May be equal to 5 .
B – May be equal to 10 .
C – May be equal to 2 .
D – None of the above.
Q.14
What is the frequency response of the circuit, taking the current as output?
A – Equal to R  jL .
B – Equal to R  1  j 2fL .
C – Equal to 1 R  j 2fL .
D – None of the above.
Q.15
The output of a circuit is related to its input by vout  3  2 vin .
Which of the following is correct?
A – The circuit is not linear.
B – Superposition applies.
C – Both A and B are wrong.
D – Both A and B are correct.
Q.16
What is the voltage of A relative to B?
A – Equal to 10 V.
B – Equal to 20 V.
C – Equal to 30 V.
D – None of the above.
Q.17
What is the impedance of the device?
A – Equal to j10 .
B – Equal to j 20 .
C – Equal to  j 20 .
D – None of the above.
Q.18
The inductor current before closing the switch is
A – Equal to 2 .
B – Equal to 2  3 .
C – Equal to 2  3 .
D – None of the above.
B.Tech. Foundation Test (Electronics) / page 5
Q.19
The capacitor voltage before closing the switch is
A – Equal to  12 .
B – Equal to 3 .
C – Equal to 18 .
D – None of the above.
Q.20
Immediately after closing the switch, the inductor voltage has a magnitude
A – Equal to 20 .
B – Equal to 15 .
C – Equal to 10 .
D – None of the above.