Soal Teori Elektronika (Lks 2010)

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Electronic Applications Page 1 / 17

LOMBA KOMPETENSI SISWA SMKTINGKAT NASIONAL XVIII Th. 2010

KELOMPOK TEKNOLOGI

JAKARTA, 12 15 MEI 2010

BIDANG LOMBA : ELECTRONIC APPLICATIONS

TUGAS I : THEORY (MULTIPLE CHOICES)

WAKTU : 120 MENIT

NILAI MAKSIMUM : 10 ( SEPULUH )

Choose the right answer and cross the number of the right answer in the blank

1. The combined resistance of two equal resistors connected in parallel is equal to :

a. the resistance of one resistor

b. twice the resistance of one resistor

c. the resistance of one resistor

d. the resistance of one resistor

e. 51 the resistance of one resistor

2. Two copper conductors have same length but one has cross-section twice that of the

other. If thicker conductor has a resistance of 20 , the resistance of the other, in

is:

a. 10

b. 40

c. 20

d. 60

e. 30

3. If the fuse is higher than required current rating is employed in a circuit:

a. it will blow more frequently since it carries more current

b. better protection will be afforded to the circuit

c. overload may seriously damage the circuit

d. maintenance cost of large fuse will be more

e. none of above


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6. SOAL TEORY LKS XVIII 2010

4. Whatever the battery voltage in fig.1, it is clear that smallest current will flow in the

resistance of :

fig.1

a. 300

b. 500

c. 200

d. 100

e. 400

5. The reading of the voltmeter V in fig.2 should be :

fig.2

a. 60 V

b. 10 V

c. 66 V

d. 0 V

e. 30 V

6. A charge of 100 coulomb is transferred in a circuit by a current of 1 A. Time taken bythis current is :

a. 0.1 s

b. 10 s

c. 1 s

d. 1000 s

e. 100 s


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7. The direction in which current-carrying conductor A of fig.3 will be forced to move is :

fig.3

a. right

b. down

c. left

d. up

e. no moving

8. In the magnetic hysteresis loop of fig.4, saturation is produced at point :

fig.4

a. Q

b. S

c. P

d. R

e. O

9. It is difficult to magnetize steel because of its:

a. high density

b. high retentively

c. low density

d. low permeability

e. high permeability


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10. Decibel is a

a. unit of power

b. unit of voltage

c. ratio of power

d. unit of current

e. unit of resistance

11. A moving-iron meter is useful for voltage measurement at :

a. ultra high frequencies

b. very high frequencies

c. high frequencies

d. low frequencies

e. supra high frequencies

12. The reading of the voltmeter in fig.5 would be nearest to :

fig.5

a. 150 V

b. 100 V

c. 200 V

d. 0 V

e. 50 V

13. The frequency of sinusoidal signal shown in fig.6 is:

a. 500 Hz

b. 25 kHz

c. 1 kHz

d. 500 kHz

e. 250 Hz

fig.6


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14. The turn-on voltage of a Ge junction diode is :

a. 0.7 V

b. 0.3 V

c. 1.0 V

d. 0.1 V

e. 3.0 V

15. In fig.7, with positive half-cycle of sinusoidal input , maximum value of Uo is :

fig.7

a. 20 V

b. 0.7 V

c. 0.3 V

d. 20 2 V

e. 20 V

16. Neglecting losses and voltage drops across secondary winding and the diode, the

value of dc output voltage Uo as read by a dc voltmeter in fig.8 is :

fig.8

a. 6.36 Vdc

b. 3.18 Vdc

c. 20 Vdc

d. 10 Vdc

e. 50 Vdc


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17. The value of DC output voltage Uo through the RL of fig.9 is:

fig.9

a. near 9 V DC

b. near 18 V DC

c. near 6.363 V DC

d. near 12.726 V DC

e. near 15.14 V DC

18. The value of current flowing through the Zener diode of fig.10 is:

fig.10

a. 5 mA

b. zero

c. 20 mA

d. infinitive

e. 50 mA

19. A NOR gate is ON only when all its inputs are:

a. ON

b. Positive

c. High

d. OFF

e. Low

20. A three input logic gate has its three inputs : X = 0, Y = 1 and Z = 1. If its output W=1,

the gate would be :

a. AND

b. NOR

c. NOT

d. OR

e. X-OR


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21.The arrangement shown in fig.11 gives the action of gate :

fig.11

a. AND

b. NOR

c. NOT

d. OR

e. X-OR

22. Four cascaded toggle flip-flops divide the input frequency by:

a. 2

b. 4

c. 8

d. 16

e. 32

23. A D flip flop can be made from a :

a. JK flip-flop

b. RS flip-flop

c. RS flip-flop and an inverter

d. Both (a) and (b)

e. Both (a) and (c)

24. The decimal number 396410 is represented by octal :

a. 47578

b. 57748

c. 74758

d. 75748

e. 75578

25. The sum of binary numbers 111112 and 000012 is given by :

a. 100100

b. 100000

c. 100001

d. 100010

e. 111000


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26. Fig.12 shows three pulse train inputs to a 3-input OR gte.

fig.12

Assuming positive logic, the output pulse train would be :

a.

b.

c.

d.

e.

Fig.13

27. In normal operation of a PNP transistor, its junction are biased :

a. both forwardb. both reverse

c. emitter-base : reverse; collector-base : forward

d. emitter-base : forward; collector-base : reverse

e. none of above

28. A common emitter connected transistor has :

a. low voltage gain

b. unity voltage gain

c. high voltage gain with 90o phase shift between the input and output

d. high voltage gain with 180o phase shift between the input and output

e. high voltage gain with 90o phase shift between the input and output


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29. With the reference to fig.14

fig.14

the base current IB is about :

a. 0.1 mA

b. 0.05 mA

c. 10 mA

d. 15 mA

e. none of above

30. With the reference to fig.14, collector current Ic is about :

a. 15 mA

b. 10 mA

c. 5 mA

d. 150 mA

e. none of the above

31. With the reference to fig.14, value of UCE is about :

a. 0 V

b. +7.5 V

c. +5 V

d. -5 V



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32. With the reference to fig.14 if the transistor is BC 549 B , value of UBE is near :

a. 0.3 V

b. 0.6 V

c. 3 V

d. 6 V


33. In the ideal transistor BC 549 shown in fig.15

fig.15

the value of Rc (in the E12) required for making URC Ucc and Ic = 2 mA is:

a. 2k7

b. 3k9

c. 3k3

d. 4k7

e. 5k6

34. With the reference to fig.15, value of RE (in the E12) is about:

a. 2k2

b. 3k3

c. 1k2

d. 1k8

e. 820


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35. With the reference to fig.15 the value of R2 (in the E12) required value of UBE=0.6V

and IR2 = 10 x IB is:

a. 3k9

b. 39k

c. 390

d. 390k

e. 39

36. With the reference to fig.15, the approximate voltage gain is most nearly:

a.1

R

RcVu

b.C

E

R

RVu

c.E

R

RcVu

d.2

1

R

RVu

e.BEr

RcVu

37. Cascade amplifiers which find wide use in ICs are :

a. direct-coupled

b. capacitive-coupled

c. transformer-coupled

d. inductively-coupled



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38. The mutual characteristic given by fig.16 is :

fig.16

a. enhancement type P-channel MOSFET

b. depletion type N-channel MOSFETc. enhancement type N-channel MOSFET

d. depletion type P-channel MOSFET


39. For the enhancement-only N-channel MOSFET, polarity of Gate Source Voltage

UGS is:

a. negative

b. positive

c. zero

d. dependent on the application of the device


40. A diac is :

a. 1-layer, 2 terminal avalanche diode

b. 2-layer, 2 terminal avalanche diode

c. 3-layer, 2 terminal avalanche diode

d. 4-layer, 2 terminal avalanche diode

e. 5-layer, 2 terminal avalanche diode


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41. A thyristor is a semiconductor device made up of :

a. four N-type layers

b. two P-type and three N-type layers

c. two P-type and two N-type layers

d. three P-type and one N-type layer

e. three P-type and three N-type layers

42. Regarding triac which statement is FALSE ?

a. it is a 5-layer bi-directional semiconductor device

b. it can be triggered in response to both positive and negative gate signals

c. it is not particularly suited for AC or main power control

d. any one of its main terminals can be used either as cathode or as anode

e. it is particularly suited for AC or main power control

43. The op-amp of fig. 17, if R2 = 1 M and R1 = 2200 , value of gain should be :

fig.17

a. 4545

b. 454.5

c. 45.45

d. 4.545


44. With the reference to fig.18, if input signal is 0,3VDC, value of output signal is:

fig.18

a. 30 V

b. 3 V

c. +15 V

d. -15 V

e. 0 V


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45. The oscillator circuit that uses a tapped coil in the tuned circuit is:

a. multivibrator

b. Hartly

c. Colpitts

d. Armstrong

e. RC oscillator

46. The function of a sync separator in TV set is to separate the:

a. video and sound signals

b. video and line sync signals

c. line sync and field sync signals

d. sound and field sync signals


47. If a persons face appears to be either too long or too short on a TV picture,

a. You should adjust vertical height control

b. You should adjust AGC

c. You should adjust vertical linearity control

d. You should adjust pin phase and pin amp control

e. You should adjust horizontal output

48. In a color TV set, alignment of three color guns to common point is known as:

a. demodulation

b. blooming

c. confetti

d. convergence

e. modulation

49. If there are 625 lines per TV picture, then lines per field are :

a. 1250

b. 312.5

c. 625

d. 2500

e. 321.5


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50. The ratio between width of TV picture and height of TV picture is called :

a. picture ratio

b. dimensional ratio

c. size ratio

d. aspect ratio

e. width ratio

51. In a CRT, focusing of electron beam is achieved by varying :

a. grid bias

b. heater voltage

c. voltage of first accelerating anode

d. secondary accelerating voltage

e. heater bias

52. An oscilloscope is generally used to measure the value of :

a. dc voltage

b. rms ac voltage

c. peak-to-peak ac voltage

d. average value of ac voltage

e. average value of dc voltage

53. If picture in a TV monitor is snowy in appearance, the defect is likely to be in :

a. tuner

b. antenna cable

c. RF amplifier

d. any one of the above three

e. none of the above three (a, b and c)

54. The circuit will have greater band pass if it has :

a. lower Q

b. higher Q

c. less resistance

d. less loading on it



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55. The FM broadcast band is from :

a. 550 kHz to 1600 kHz

b. 88 kHz to 108 kHz

c. 88 MHz to 108 MHz

d. 88 GHz to 108 GHz

e. 88 Hz to 108 Hz

56. A half-wave dipole at a frequency of 100 MHz has length of :

a. 100 m

b. 3 m

c. 1.5 m

d. 0.75 m

e. 27 m

57. A degaussing coil is used for:

a. demagnetizing transformer cores

b. demagnetizing color picture tubes

c. rotating directional antennas

d. trap inductors

e. color killer

58. The value of SWR for a transmission line of characteristic impedance ZO when

feeding a load of impedance ZL is :

a. SWR = ZO x ZL

b. SWR = ZO/ZL

c. SWR = ZO + ZL

d. SWR = ZL/ZO

e. SWR = ZO - ZL


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6 SOAL TEORY LKS XVIII 2010

59. The relationship between inductance and capacitance per unit length and

characteristic impedance of a transmission line is :

a. ZO = LC

b. ZO = CL /

c. ZO = LC/

d. ZO = 2 LC

e. ZO = 2 CL /

60. A transmission line having ZO = 75 is delivering power to a 300 load. Its SWR is :

a. 1 : 4

b. 4 : 1

c. 1 : 2

d. 1 : 1

e. 2 : 1

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Soal Teori Elektronika (Lks 2010)