Chapter # 16 Electromagnetics Waves and Electronics

PHYSICS

CHAPTER # 16 Electronics

1.

 When the magnetic flux changes at the rate of t , then at distance “r”, the intensity of induced electric field is _______: 1   A a) E = 2r . t b) E = 2  r . t 1  c) E = 3r . t

2.

3.

 d) E = 2  r2 . t

 When an electric flux changing at the rate of t , then the strength of magnetic field “B” is given as: 0  e 1 0 2r 2  r t B a) E = b) B =

B

0  e 0 t c) B = r d) None of these According to Maxwell, the velocity of electromagnetic waves is _______ in shape: 1 1 a)

4 e 0 1

b)

e 2 e10  1

C

0

1 0  0

4.

5. 6. 7. 8. 9.

0 c) d) According to electric field between two charged plates, we can say that a changing electric flux creates _______: A a) Magnetic field b) Perpendicular c) Permeability d) None of these The field produces electromagnetic waves when an accelerating field is applied to a _______: a) Magnetic field b) Charge B c) Direction d) None of these The electromagnetic waves travel in free space with the speed of _______: a) Light b) Strength A c) Sound d) None of these Velocity of electromagnetic waves depends upon _______ and electric permittivity: a) Longitude b) Magnetic permeability B c) Electric field d) None of these Electromagnetic waves emitted from _______ are transverse: a) Antenna b) Coil A c) Wire d) Straight The natural frequency of an L.C. circuit is _______: 1 a) Antenna 1

10. 11. 12. 13. 14.

b)

2 LC

B

c) 3 LC d) None of these The frequency range of electromagnetic waves is _______: a) 106 Hz b) 108 Hz 9 c) 10 Hz d) 1011 Hz The velocity of electromagnetic waves and the velocity of light have _______ value: a) Different b) Same c) Opposite d) None of these Sound waves travel with a speed _______ at 0oC: a) 340 m/s b) 350 m/s c) 310 m/s d) 330 m/s We can convert sound waves into electrical oscillations by _______: a) Microphone b) Television c) Radio d) None of these The frequency range (20 – 20,000 Hz) is called _______ range: a) Audible b) Simple c) Electromagnet d) None of these Bahadur Ali Qureshi

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PHYSICS

CHAPTER # 16 Electronics

15. 16.

17. 18. 19. 20. 22. 24. 25. 26. 27. 28. 29. 30. 31. 32.

33.

34. 35. 36.

_______ is used for the rectification of the electromagnetic waves: a) Audible b) Compare c) Crystal diode d) Valence band A geometrical shape which consists of a diagram like square in each side. If we arranged all the atoms or molecules in different points, then we said that this structure is called _______: a) Molecule b) Atom c) Crystal d) None of these There are _______ ways of space lattice: a) 14 b) 15 c) 16 d) 19 The figure in which eight atoms or molecules are lies at eight corners are called _______: a) Simple cube b) Face cube c) Free electron d) Simple square The band theory gives us the simple idea about the classification of _______: a) Liquids b) Energy c) Solids d) Atom The highest energy level is completely filled in an _______: a) Insulator b) Semi-conductor c) Electron d) None of these The some electrons move from one level to another in _______ band: a) Semi-conductor b) Insulator c) Energy d) None of these The value of resistivity for insulator is of the order of _______: a) 10-4 ohm - meter b) 108 ohm - meter 6 c) 10 ohm - meter d) 1010 ohm - meter The substances which have intermediate values of resistivity are called _______: a) Semi-conductors b) Electrons c) Circle d) Overlap The crystals of Germanium and Silicon are the examples of _______: a) Electrons b) Semi-conductors c) Conductors d) None of these A pure semiconductor behaves like an insulator at _______ temperature: a) 120oC b) 140oC c) Absolute Zero d) 90oC The conduction due to charges produced by pair generation is called _______ conduction: a) Intrinsic b) Hole c) Full d) None of these The pair production and intrinsic conductivity both are low at _______: a) Road temperature b) Hall temperature c) Room temperature d) None of these We add impurities such as _______, we can gain an N-types semi-conductors: a) Antimony, phosphorous or Arsenic b) Carbon, oxygen and Nitrogen c) Arsenic and oxygen d) None of these The P-type semi-conductor is obtained by adding impurity materials: a) Carbon, Oxygen and Nitrogen b) Boron, Indium or Gallium c) Arsenic and Oxygen d) None of these The germanium or silicon crystal formed after adding pentavalent impurity is known as _______ substances: a) N-type b) S-type c) Q-type d) None of these The single crystal of germanium or silicon, formed after adding a trivalent impurity is known as _______ substance: a) N-type b) P-type c) Q-type d) R-type As the conduction in a P-type substances takes place due to holes, so they are known as _______: a) Majority carriers b) Minority carriers c) P-type d) N-type Electrons in a P-type substance due to thermal pair-generation are known as _______: a) Majority carriers b) Minority carriers c) P-type d) N-type At 0oK, a semi-conductor acts like _______: a) P-type b) Minority carriers c) Insulator d) None of these Bahadur Ali Qureshi

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C

C

A A C A A B A B C A C A B

A

B

A B C

PHYSICS

CHAPTER # 16 Electronics

37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 52. 53. 54.

55.

56. 57.

The conversion of alternating current (A.C) into direct current (D.C) is called _______: a) Reflection b) Rectifier c) Reactivity d) None of these There are _______ main types of rectifiers: a) Four b) Three c) Two d) Nine In full wave rectifier, _______ diodes are used: a) Two b) One c) Three d) Five LEDs are used in _______ watches: a) Hand b) Digital c) Simple d) None of these LEDs are used in _______ calculators: a) Electronic b) Digit c) Lamp d) Panel A photo diode is a semi-conductor device usually made from _______: a) Nitrogen b) Oxygen c) Carbon d) Silicon A photo voltaic cell converts light energy into _______ energy: a) Electrical b) Simple c) Metal d) Diode _______ cells are used in satellites and space vehicles: a) Electric b) Photo c) Positive d) Diode Transistor is a semi-conductor device which can amplify both the current as well as _______: a) Ampere b) Transistor c) Voltage d) None of these There are _______ main types of transistors: a) Two b) Three c) Five d) Four The two transistor are P-n-P transistor and _______: a) n-P-n transistor b) n-n-p transistor c) p-p-n transistor d) None of these The middle portion of the transistor is called _______: a) Middle point b) Base c) Perpendicular d) Transistor The process which converts low voltage signals to high voltage is called _______: a) Amplification b) Transistor c) Output d) Input The semi-conductor diode has the property of _______: a) Negative b) One way conduction c) Two way conduction d) None of these The transistor was invented by _______: a) John Bardeen b) Henry c) John Henry d) Joule The changing magnetic flux causes induced emf which produces electric field in the region. With distance from the region of changing magnetic flux, the electric field intensity: a) Decreases inversely b) Increases inversely c) Increases directly d) Remains unchanged When magnetic flux changes, an induced emf is produced, which generates electric field in the region. The strength of the electric field depends upon: a) The magnetic flux b) Change of magnetic flux c) Rate of change of magnetic flux d) None of these A changing electric flux develops in the region: a) An electric field b) A magnetic field c) Gravitational field d) None of these The changing electric flux gives rise to: a) Electromagnetic waves b) Sound waves c) Water waves d) None of these

Bahadur Ali Qureshi

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B C A B A D A B C A A B A B A

A

C

B A

PHYSICS

CHAPTER # 16 Electronics

58.

59. 60. 61. 62. 63. 64.

65. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77.

Electromagnetic waves consist of: a) Electric and magnetic fields moving parallel to each other b) Electric and magnetic fields moving at right angle to each other c) Electric field moving with velocity of light d) Magnetic field moving with velocity of light Electromagnetic waves propagate in free space with the speed of: a) Electrons b) Sound c) Light d)  -particle Which of the following are electromagnetic waves: a) Light waves b) Sound waves c) Water waves d) Waves along a stretched string Which of the following are not electromagnetic waves: a) Light waves b) X-rays c) Heat waves d) Sound waves Which of the following is transported by electromagnetic waves: a) Current b) Matter c) Energy d) Charge Which waves are emitted from antenna: a) Stationary waves b) Longitudinal waves c) Transverse waves d) Sound waves The resonant frequency of an LC circuit is given by: 1 LC a) f = 2 b) f = 2 LC 2 LC c) f = 2 d) f = LC Electromagnetic wave transmitted by an antenna have frequency of the order of: a) 102 Hz b) 104 Hz 6 c) 10 Hz d) 1012 Hz A crystal is said to be face centred when one extra atom (or molecule) lies at eh centre of: a) Two sides b) Four sides c) Each of the six faces of the cube d) The cube A completely filled band is called: a) Valence band b) Conduction band c) Forbidden band d) None of these Near absolute zero temperature pure semi-conductors behave like: a) Conductors b) Metals c) Insulators d) None of these Semiconductors have resistivity of the order of: a) 108 ohm-m b) 106 ohm-m 4 c) 10 ohm-m d) 102 ohm-m Germanium and Silicon are the materials used as: a) Conductors b) Semi-conductors c) Insulators d) None of these The outer most orbit of each atom in silicon contains: a) Four electrons b) Two electrons c) Eight electrons d) No electrons Which one of the following is not a semi-conductor: a) Silicon b) Germanium c) Diamond d) Gallium N-type materials are obtained by dopping intrinsic germanium with: a) Trivalent impurity atoms b) Pentavalent impurity atoms c) Tetravalent impurity atoms d) None of these P-type materials are obtained by adding germanium with: a) Tetravalent impurity atoms b) Trivalent impurity atoms c) Pentavalent impurity atoms d) None of these The charge carries in N-type materials are: a) Electrons b) Holes c) Protons d) Positive ions The charge carries in P-type substances are: a) Protons b) Electrons c) Holes d) Negative ions Bahadur Ali Qureshi

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B

C A D C C

B

C C B C C B A C B B A C

PHYSICS

CHAPTER # 16 Electronics

78. 79. 80. 81. 82. 83. 84. 85. 86. 87. 88. 89. 90. 91. 92. 93. 94. 95. 96. 97. 98.

Which of the following is acceptor impurity: a) Antimony b) Gallium c) Silicon d) Arsenic Which of the following is donor impurity: a) Arsenic b) Indium c) Germanium d) Carbon Minority carriers in N-type substances are: a) Holes b) Electrons c) Protons d) Positive ions Minority carriers in P-type substances are: a) Holes b) Electrons c) Negative ions d) Protons Majority carriers in P-type substances are: a) Electrons b) Holes c) Positrons d) Negative ions Majority carriers in N-type substances are: a) Protons b) Holes c) Electrons d) Positive ions The vacant electron site when a bond is broken is called: a) A positive ion b) A deutron c) A hole d) An electron Hole is equivalent to: a) A neutral particle b) A positive charge c) A negative charge d) An electron A semiconductor diode when forward biased offers: a) High resistance b) Infinite resistance c) Low resistance d) None of these A PN junction conducts only when it is: a) Reverse biased b) Forward biased c) Neither reverse nor forward biased d) All of these The width of the depletion region in a PN junction depends on the: a) Doping of p-materials b) Doping of n-materials c) Doping of both the p and n-materials d) None of these When the PN junction is forward biased, the width of the depletion region: a) Increases b) Decreases c) Remains the same d) None of these The forward current through a semi-conductor diode circuit is due to: a) Majority carriers b) Minority carriers c) Holes d) Electrons The reverse current through a semi-conductor diode circuit is due to: a) Majority carriers b) Minority carriers c) Electrons d) Holes Rectification is the process of converting: a) A.C into D.C b) D.C into A.C c) Both A.C into D.C and D.C into A.C d) None of these The device used for conversion of A.C into D.C is called: a) A detector b) An oscillator c) An amplifier d) A rectifier In full wave rectification, the output D.C voltage is obtained across the load for: a) The complete cycle of input A.C b) The negative half cycle of input AC only c) The positive half cycle of input AC only d) None of these In half-wave rectification, the output DC voltage is obtained for: a) The negative half cycle of input AC only b) The positive half cycle of input AC only c) The negative and positive half cycles of input AC d) None of these The specially designed semi-conductor diodes used as fast counters in electronic circuit are: a) Solar cells b) Light emitting diodes c) Photo diodes d) None of these The specially designed semiconductor diodes used as indicator lamps in electronic circuits are: a) Light emitting diodes b) Photo diodes c) Solar cells d) Photo voltaic cells Solar cell (or photo voltaic cell) is a device which converts: a) Chemical energy into electrical energy b) Light energy into electrical energy c) Electrical energy into light energy d) Chemical energy into light energy Bahadur Ali Qureshi

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B A A B B C C B C B C B A B A D A B C A B

PHYSICS

CHAPTER # 16 Electronics

99.

100. 101. 102. 103. 104. 105.

106. 107. 108.

109. 110. 111. 112.

When a transistor is used in a circuit, normally: a) The emitter-base junction is forward biased and the collector-base junction is reverse biased b) The emitter-base junction is reverse biased and the collector-base junction is forward biased c) Both the junctions are reverse biased d) Both the junctions are forward biased A transistor can be used as: a) A voltage amplifier b) A current amplifier c) An oscillator d) All of the above Solar cells are thin sandwich of: a) Semi conductors b) Insulators c) Conductors d) Wood The material used in making (fabricating) solar cells is: a) Carbon b) Iron c) Silicon d) Mercury Which one of the following is not an acceptor impurity: a) Gallium b) Indium c) Boron d) Arsenic Waves used for radio transmission have wavelength: a) Greater than that of infra-red rays b) Smaller than that of infra-red rays c) Smaller than that of ultraviolet rays d) None of these Which of the following have smaller wavelength: a)  -rays b) X-rays c) Ultraviolet rays d) Infra-red rays The direction of magnetic field in an electromagnetic wave is: a) Parallel to the electric field b) Perpendicular to the electric field c) At an angle of 60o with the electric field d) None of these The velocity of an oscillating charge as it moves to and fro along a wire is always: a) Constant b) Changing c) Zero d) None of these With the rise of temperature, the conductivity of a pure semi-conductor: a) Increases b) Decreases c) Remains constant d) Some times decreases and sometimes increases The band theory of solids successfully classifies the solids into: a) Semi conductors only b) Conductors only c) Insulators only d) All of these The base of the transistor should be of: a) High doping b) Low doping c) Zero doping d) None of these A semi conductor diode cannot be used as: a) A detector b) A modulator c) A rectifier d) An amplifier On doping the conductivity of the semi conductor: a) Decreases b) Increases c) Remains same d) All of these

Bahadur Ali Qureshi

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A

D A C D A A B B

A

D B D B