ELECS- APRIL 3, 2017

59. In the circuit of figure, the switch is closed at t = 0. At t = 0 the current through C is [SEE DRIVE FOR PICTURE] A. 4 A B. 2.5 A C. 3.1 A D. 0

A

60. A power transistor dissipates 5 W. If ambient temperature is 30° and case to air thermal resistance is 10° C/W, then case temperature is A. 80°C B. 20°C C. 32°C D. 305°C

A

74. An RLC series circuit is fed form 100 V ac supply. Inductance is 1 H and Q = 7.5. At resonance, the voltage across inductance is A. 750V B. 100 V C. about 13.5 V D. 1500 V

A

76. As temperature increases, the temperature coefficient of a metal A. decreases B. increases C. remains unchanged D. any of the above

A

18. What is the common use of a varactor diode? A. As a voltage controlled inductance. B. As a voltage controlled capacitance. C. As a constant voltage source. D. As a constant current source.

B

14. What component of a transformer provides the path for magnetic lines of flux? A. Secondary winding B. Load C. Primary winding D. Core

C

3. An RL series circuit has an impedance of 20 ohms when frequency is 25 Hz. At f = 50 Hz, the impedance will be A. 40 ohms B. 20 ohms C. less than 40 ohms but more than 20 ohms D. less than 20 ohms but more than 40 ohms

C

30. In a class C power amplifier the input signal has a frequency of 250 kHz. If the collector current pulses are 0.1 μs wide, what is the duty cycle of current waveform? A. 50% B. 25% C. 2.5% D. 0.25%

C

36. If two equal frequency ac signals of exactly 5 V each are combined with one of the signals 180 degrees out of phase with the other, what will be the value of the resultant voltage? A. 10 V B. 5.0 V C. 0 V D. 2.0 V

C

39. What is the commonly used IC package for digital IC's? A. Flat pack B. Dip ceramic C. DIP plastic D. Plastic IC

C

42. In a crystal, A. the frequencies of series and parallel resonance are equal B. the frequency of series resonance is more than frequency of parallel resonance C. the frequency of parallel resonance is more than frequency of series resonance D. None of the above

C

44. In the circuit of figure shown, the diode [SEE DRIVE FOR PICTURE] A. will conduct as the whole cycle B. will conduct in the positive half cycle C. will not conduct D. will conduct from 30° to 150° in the positive half cycle

C

64. A transformer with 100 turns in the primary winding and 25 turns in the secondary winding is which of the following? A. A step-up transformer B. An isolation transformer C. A step-down transformer D. An autotransformer

C

67. In a two stage CE amplifier circuit, the ac collector resistance of the first stage depends on A. load resistance B. input impedance of first stage C. input impedance of second stage D. All of the above

C

82. A digital voltmeter has a read out range from 0 to 999 counts. If the full scale reading is 9.999 V, the resolution is A. 1 V B. 0.01 V C. 1 mV D. 1 μV

C

93. What is the purpose of the rectifier section in a power supply? A. To change pulsating DC to pure DC. B. To increase the AC value. C. To change AC to pulsating DC. D. To lower the AC value.

C

95. In a CE amplifier, A. both ac and dc load lines have the same slope B. the ac load line has more slope than dc load line C. the ac load line has less slope than dc load line D. the two load lines may have slope more than the other

C

13. The moving coil-current in a wattmeter is proportional to the ____ across the circuit. A. voltage B. power C. resistance D. current

A

19. The self bias provides A.stable Q point B. large voltage gain C. high input impedance D. high base current

A

31. The value of parameter used in re transistor model A. increases with increase in temperature B. decreases with increase in temperature C. is not affected by increase in temperature D. either (B) or (C)

A

33. It is a heavily doped PN junction that exhibits negative resistance over part of its range of operation. A. Tunnel diode B. Varactor C. SCR D. Zener diode

A

37. In a N-P-N transistor, when emitter junction is forward biased and collector junction is reverse biased, the transistor will operate in A. active region B. saturation region C. cut of region D. inverted region

A

40. In the figure shown, what is the current supplied by battery immediately after switching on the circuit? [SEE DRIVE FOR PICTURE] A. 1 A B. 4 A C. 10 A D. 0

A

43. What is the phase relationship between current and voltage in an inductor? A. Current lags voltage by 90 B. Current lags voltage by 180 C. Voltage lags current by 90 D. In phase

A

45. What is the magnetic equivalent of electrical resistance? A. Reluctance. B. Magnetomotive force. C. Flux. D. Magnetic field.

A

49. In the figure below, VEB = 0.6 V, β = 99. Find VC and IC. [SEE DRIVE FOR PICTURE] A. 9.3 V and 1.98 mA respectively B. 4.6 V and 1.98 mA respectively C. 9.3 V and 0.02 mA respectively D. 4.6 V and 0.02 mA respectively

A

55. How is an ammeter connected to the circuit under test? A. In series B. Shunted C. Series-parallel D. In parallel

A

56. An RLC series circuit is underdamped. To make it overdamped, the value of R A. has to be increased B. has to be decreased C. has to be increased to infinity D. has to be reduced to zero

A

57. The current that flows in the primary of a transformer with the secondary open (or no load is attached) is ______ current. A. source B. exciting C. load cur D. coupling

A

63. A battery with capacity of 100 Ah and 12 volts rating will run an electronic equipment at exactly 20 hours, how much power is needed? A. 60W B. 20 W C. 10 W D. 30 W

A

65. A full wave rectifier circuit using centre tapped transformer and a bridge rectifier are fed at 100 V, 50 Hz. The frequencies of outputs in these two rectifiers are A. 100 Hz each B. 50 Hz each C. 100 Hz and 50 Hz D. 50 Hz and 100 Hz

A

70. For the circuit shown in the figure, what is the current I? [SEE DRIVE FOR PICTURE] A. Indeterminate due to indeterminate data B. zero C. 4 Amp D. 8 Amp

A

75. The quiescent collector current IC, and collector to emitter voltage VCE in a CE connection are the values when A. ac signal is zero B. ac signal is low C. ac signal is negative D. Either (A) or (B)

A

78. In a push pull circuit A. each transistor conducts for 180° B. each transistor conducts for more than 180° but less than 360° C. each transistor conducts for less than 180° D. the period of conduction of each transistor depends on circuit configuration

A

84. A voltmeter using thermocouples measures A. rms value B. peak value C. average value D. peak to peak value

A

88. A two-branch parallel tuned circuit has a capacitance C in one of the two branches and resistance R in second branches. As C is decreased, the dynamic resistance A. increases B. decreases C. remains constant D. may increase or decrease

A

9. In Kirchhoff''s current law, which terminal of a resistance element is assumed to be at a higher potential (more positive) than the other? A. The terminal where the current enters the resistance elements. B. The terminal where the current exits the resistance elements. C. Either A or B can be arbitrarily selected. D. The terminal closest to the node being analyzed.

A

91. Which is class AB amplifier? A. Output is present for more than 180 degrees but less than 360 degrees of the signal input cycles. B. Output is present for less than 180 degrees of the input signal cycle. C. Output is present for exactly 180 degrees of the input signal cycle. D. Output is present for the entire input signal cycle

A

94. Wave A = 100 sin ωt and wave B = 100 cos ωt. Then A. rms values of the two waves are equal B. rms values of A is more than that of B C. rms values of A is less than that of B D. rms values of the two waves may or may not be equal

A

96. Two series connected 7 H inductors are adjacent to each other. Their coefficient of coupling is 0.64. What is the value of mutual inductance? A. 4.48 H B. 0.448 H C. 44.8 H D. 448 H

A

97. In an R-C series circuit excited by a voltage E, the charge across capacitor at t = 0 is A. 0 B. EC C. EC (1 - e^(-t/RC)) D. infinity

A

99. The electrical energy required to heat a bucket of water to a certain temperature is 2 kWh. If heat losses are 25%, the energy input is A. 2.67 kWh B. 3 kWh C. 2.5 kWh D. 3.5 kWh

A

10. An indication of the current supplying capability of the battery for a specific period of time, e.g. 400 AmpereHour. A. Rating B. Capacity C. Capability D. Current load

B

15. If an electronic resistor do not have the fourth color strip it means it has a tolerance of ____ A. 0 % B. 20 % C. 10 % D. 100 %

B

16. How do you increase the range of a voltmeter? A. Through two-series resistors. B. Through multipliers. C. Through shunt resistors. D. Through series resistors.

B

21. A parallel plate capacitor with air as dielectric has a capacitance C. If the dielectric has a dielectric constant ∈r and the remaining dimensions are the same, the capacitance will be A. C/∈r B. ∈rC C. ∈2rC D. ∈3rC

B

27. A bulb rated at 60 W, 120 V is used for 30 minutes. The charge associated with this operation is A. 3600 C B. 900 C C. 7200 C D. 600 C

B

32. A thyristor has a maximum allowable junction temperature of 120°C and the ambient temperature is 40°C. If thermal resistance is 1.6° C/W, what is the maximum allowable internal power dissipation? A. 20 W B. 50W C. 92 W D. 128 W

B

34. In a power supply, what percent regulation is ideal? A. 10 % B. 0 % C. 100 % D. 98 %

B

35. What device deposits materials on a substrate in desired patterns? A. Thin film B. Mask C. Plate D. Wafer

B

38. Emitter follower is used for ____ A. current gain B. impedance matching C. voltage gain D. current regulator

B

41. What limits the maximum forward current in a junction diode? A. The peak inverse voltage B. The junction temperature C. The forward voltage D. The back EMF

B

47. The current rating of a cable depends on A. length of cable B. diameter of cable C. both length and diameter of cable D. the applied source

B

51. A series RC circuit has R = 5 Ω and C = 10 μF. The current in the circuit is 5 sin 20000t. What is the applied voltage? A. 252 sin (20000t + 45°) B. 252 sin (20000t - 45°) C. 252 sin 20000t D. 252 sin (20000t - 90°)

B

54. The reason why the rheostat of an ohmmeter needs to be adjusted is ______. A. balance the resistance of circuit being measured B. due to aging meter battery C. decrease in meter temperature D. increase in meter temperature

B

6. Find Q of a circuit when the resonant frequency is 14.128 MHz, the inductance is 2.7 uH and the resistance is 18,000 ohms are in parallel. A. 751 B. 75.1 C. 7.51 D. 71.5

B

66. In a voltage regulated power supply the zener operates in the breakdown region when (Vin is input voltage and Vz is zener breakdown voltage) A. Vin < Vz B. Vin > Vz C. Vin = Vz D. Both (A) or (B)

B

68. The gain of an FET amplifier can be changed by changing A. rm B. gm C. Rd D. RL

B

73. A current of 1 A in the coil of an iron cored electromagnet cause a flux density of 0.2.T. If the current is 2 A, what is the flux density? A. 0.2 T B. 0.4T C. 0.4 T or less D. 0.4 T or more

B

8. Three resistance of 15 ohms each are connected in delta. The resistance of equivalent star will have a value of A. 15 ohms B. 5 ohms C. 5/3 ohms D. 45 ohms

B

85. A dynamometer wattmeter is connected in ac circuit. The measured power is A. rms power B. average power C. peak power D. instantaneous power

B

89. What is the half-power bandwidth of a parallel resonant circuit which has a resonant frequency of 7.1 MHz and Q of 150? A. 25.1 kHz B. 47.3 kHz C. 411 kHz D. 20.5 kHz

B

92. Determine from the following the advantage of full wave rectifier over the have wave rectifier. A. That the ripple frequency is lower. B. That the diodes will conduct during both halves of the input cycle. C. That there exist the lower temperature during both halves of the cycle. D. Each diode can cool-off during halves of the input cycle.

B

100. What is the voltage drop across the resistor in an RC charging circuit when the charge on the capacitor is equal to the battery voltage? A. 0.10 volt B. 1.0 volt C. zero D. 10 volts

C

11. For a base current of 10 μA, what is the value of collector current in common emitter if βdc = 100. A. 10 μA B. 100 μA C. 1 mA D. 10 mA

C

12. Determine the resonant frequency of a circuit when L is 40 uH and C is 6 pF are in series. A. 10.3 kHz B. 11.5 kHz C. 10.3 MHz D. 11.5 MHz

C

17. Which of the following refers to the important characteristic of a three-terminal regulator? A. Maximum and minimum input voltage, maximum output current and voltage. B. Maximum and minimum input voltage, minimum output voltage and maximum output voltage. C. Maximum and minimum input voltage, minimum output current and maximum output voltage. D. Maximum and minimum input voltage, minimum output current and voltage.

C

20. How can the true power be determined in a circuit where the ac voltage and current are out of phase? A. By subtracting the apparent power from the power factor. B. By dividing the apparent power by the power factor. C. By multiplying the apparent power times the power factor. D.By multiplying the RMS voltage times the RMS current.

C

22. Two thyristor of same rating and same specifications A. will have equal turn on and turn off periods B. will have equal turn on but unequal turn off periods C. may have equal or unequal turn on and turn off periods D. will have unequal turn on and turn off periods

C

24. The principle behind the operation of a crystal is ____ effect. A. ionization B. thermionic C. piezoelectric D. photoelectric

C

29. The open loop gain of an amplifier is 200. If negative feedback with β = 0.2 is used, what is the closed loop gain? A. 200 B. 40.12 C. 4.878 D. 2.2

C

46. Which of the following alloy does a manganin made of? A. Chromium, copper and lead. B. Zinc, copper and lead. C. Copper, manganese and nickel. D. Copper, aluminum and chromium.

C

58. What electrical property is measured by an ammeter? A. Power B. Voltage C. Current D. Resistance

C

61. To prevent a DC return between source and load, it is necessary to use A. resistor between source and load B. inductor between source and load C. capacitor between source and load D. Either (A) or (B)

C

62. What is the characteristic of the current flow in a parallel R-L-C circuit at resonance? A. The current circulating in the parallel elements is zero. B. The current circulating in the parallel elements is dc. C. The current circulating in the parallel elements is at a maximum. D. The current circulating in the parallel elements is at a minimum.

C

7. A transistor has two p-n junctions. The batteries should be connected such that A. both junctions are forward biased B. both junctions are reverse biased C. one junction is forward biased and the other is reverse biased D. either A or B

C

71. A "picture" of a circuit which uses symbol to represent the various components. A. Circuit representation B. Circuit drawing C. Schematic diagram D. Drawing

C

79. To increase Q factor of a coil, the wire should be A. long B. thin C. thick D. long and thin

C

80. Which of the following voltmeters would you use for measuring voltage across 20 kΩ resistance? A. Voltmeter having a resistance of 5 kΩ B. Voltmeter having a sensitivity of 1 kW/V C. Voltmeter having sensitivity of 10 kW/V D. None of the above

C

81. Two resistors R1 = 36 Ω ± 5% and R2 = 75 Ω ± 5% are connected in series. The total resistance is A. 111±0Ω B. 111 ± 2.778 Ω C. 111 ± 5.55 Ω D. 111 ± 7.23 Ω

C

83. Potentiometer method of dc voltage measurement is more accurate than direct measurement using a voltmeter because A. it loads the circuit to maximum extent B. it loads the circuit moderately C. it does not load the circuit at all D. it uses centre zero galvanometer instead of voltmeters

C

86. What is the effect of connecting battery cells in parallel? A. Current decreases B. Voltage increases C. Current increases D. Voltage decreases

C

1. If three shielded 100 mH coils are connected in series, what is the total effective inductance? A. 67.777 mH B. 100 mH C. 33.333 mH D. 300 mH

D

2. The dc load current in a bridge rectifier circuit is 10 mA. What is the dc load current through each diode? A. 40 mA B. 20 mA C. 10 mA D. 5 mA

D

23. Two coils have their axes perpendicular to each other. The coefficient of coupling k is A. 1 B. 0.5 C. more than 0 but less than 1 D. 0

D

25. The type of impurities in p-type semiconductor like boron and gallium is ____. A. covalent B. bivalent C. pentavalent. D. trivalent

D

26. In a BJT circuit a pnp transistor is replaced by npn transistor. To analyze the new circuit A. all calculations done earlier have to be repeated B. replace all calculated voltages by reverse values C. replace all calculated currents by reverse values D. replace all calculated voltages and currents by reverse values

D

28. In the figure shown, A1, A2, A3 are identical Ammeters. If A1 and A3 read 5 and 13 A respectively, reading of A2 will be [SEE DRIVE FOR PICTURE] A. 8 B. 13 A C. 18 D. 12 A

D

4. Determine the average voltage (Vave) output of a full wave rectifier with an output of 100 volts peak. A. 14.14 V B. 6.37 V C. 141.4 V D. 63.7 V

D

48. What type of pn diode is formed by using a fine metal and a section of n-type semiconductor material?. A. Fused. B. Interface. C. Alloyed. D. Point-contact.

D

5. A current is flowing through a conductor with non-uniform area of cross-section. Then A. current will be different at different cross sections B. current will be the same at all the cross-sections C. current will be different but current density will be same at all the cross-sections D. current will be the same but current density will be different at different cross-sections

D

50. The load impedance ZL of a CE amplifier has R and L in series. The phase difference between output and input will be A. 180° B. 0 C. more than 90° but less than 180° D. more than 180° but less than 270°

D

52. When the ac base voltage in a CE amplifier circuit is too high, the ac emitter current is ______. A. zero B. constant C. alternating D. distorted

D

53. Si transistor of following figure has a = 0.9 and ICE= 0, VEE = 5 V and VCC = 13 V, then RE will be if IEQ = 1 mA [SEE DRIVE FOR PICTURE] A. 3 kΩ B. 4 kΩ C. 5 kΩ D.4.3 kΩ

D

69. Two phasors having rms values V1 and V2 which are added to give a phasor having rms value V3. V3 is maximum if phase angle between V1 and V2 is A. 90° B. 180° C. 270° D. 360°

D

72. In a RL circuit, the angle, θ by which the current lags the voltage is A. 0>θ>-90° B. 90° C. 0° D. 0<θ<90°

D

77. The figure below is a 24 V, stabilized power supply. The zener is 24 V, 600 mW. The minimum zener current is 10 mA. What are the proper values R and maximum load current? [SEE DRIVE FOR PICTURE] A. 320 Ω, 10 mA B. 400 Ω, 15 mA C. 400 Ω, 10 mA D. 320 Ω, 15 mA

D

87. The input impedance of op-amp circuit of figure is [SEE DRIVE FOR PICTURE] A. 120 kohm B. 110 kohm C. infinity D. 10 kohm

D

90. In the circuit of figure shown below, what is the voltage across capacitor at t = ∞? [SEE DRIVE FOR PICTURE] A. 0 V B. 20 V C. very large D. 7.5V

D

98. A wire has a resistance R ohm. If another wire of the same material and same weight has double the diameter (as compared to the first wire), the resistance of the second wire will be A. 0.5 R B. 0.25 R C. 0.125 R D. R/16

D