2nd Year Physics Chapter 18 Electronics Notes MCQs Solutions

physics 12th notes mcqs chapter 18

1. The crystal of Germinium or silicon in its pure form at absolute zero acts as:

 
 
 
 

2. The output of two inputs OR gate is 0 only when its

 
 
 
 

3. The pulsating output voltage of a rectifier can be made smooth by using a circuit known as:

 
 
 
 

4. Base of the transistor is very thin of the order of

 
 
 
 

5. The process of turning an alternating current waveform into a direct current waveform is called:

 
 
 
 

6. A Light emitting diodes (LED) are made from semi-conductors:

 
 
 
 

7. Junction used as indicator in electronic circuits is:

 
 
 
 

8. The potential barrier for germanium at room temperature is

 
 
 
 

9. Which diode works at reverse biasing?

 
 
 
 

10. In npn transistor current does not flow in the direction from

 
 
 
 

11. In a transistor which one is very thin:

 
 
 
 

12. The width of central region of a transistor is

 
 
 
 

13. The diode cannot be used as

 
 
 
 

14. If a reverse current of a reverse biased junction is increased to a maximum value then:

 
 
 
 

15. Gain of inverting op-amp in the R1=α and r²=0

 
 
 
 

16. The common door bell requires a voltage of about

 
 
 
 

17. The potential difference across depletion region in case of Ge is:

 
 
 
 

18. Automatic functioning of streetlight can be done by the use of:

 
 
 
 

19. An operational amplifier have how many input terminals:

 
 
 
 

20. A transistor consists of three electrical contact which one of these is rectifying:

 
 
 
 

21. The gain of transistor amplifier depends upon

 
 
 
 

22. Greater concentration of impurity is added in:

 
 
 
 

23. LDR means

 
 
 
 

24. Reverse resistance of p-n junction is:                

 
 
 
 

25. The average gap for Germanium at OK is:                   

 
 
 
 

26. Types of transistors are:

 
 
 
 

27. The central region of n-p-n transistor is known as:

 
 
 
 

28. A pn junction cannot be used as:           

 
 
 
 

29. In half wave rectification, the output DC voltage is obtained across the load for:

 
 
 
 

30. In reverse biasing a p-n junction offers

 
 
 
 

31. The circuit of full wave rectification consist of:

 
 
 
 

32. The specially designed semi conductor diodes used as indicator lamps in electronic circuits are:

 
 
 
 

33. In p-n-p transistor, the current flows in the direction from:

 
 
 
 

34. In order that a transistor acts as switch, a larger positive potential is applied across its:

 
 
 
 

35. Photo voltaic cell is also called:

 
 
 
 

36. When p-type of p-n-junction connected to positive end and N-type of the junction connected to the negative terminal of battery then the junction is:

 
 
 
 

37. In full wave rectification, the output DC voltage is obtained across the load for:

 
 
 
 

38. Photodiode detects

 
 
 
 

39. The pn junction on forward biasing acts as:                 

 
 
 
 

40. When light emitting diode is forward biased, it emits light of colour:

 
 
 
 

41. Photo diode can be used as:

 
 
 
 

42. The potential difference develops in case of Ge is

 
 
 
 

43. Universal gate is the gate which can perform the function of:

 
 
 
 

44. A photo diode is used for

 
 
 
 

45. Depletion region has:                   

 
 
 
 

46. The term transistor stands for:               

 
 
 
 

47. If positive terminal of the battery is connected to n-type and negative terminal is connected to p type then diode is:

 
 
 
 

48. In photovoltaic cell, current is directly proportional to:

 
 
 
 

49. Process of conversion of A.C. into D.C. is called

 
 
 
 

50. Holes are exist in:              

 
 
 
 

51. Semi-conductor diode conducts only when it is

 
 
 
 

52. For normal operation of a transistor, the E-B junction is always

 
 
 
 

53. When a transistor is used in a circuit generally:

 
 
 
 

54. A single photo voltaic cell produces a current of:

 
 
 
 

55. Which factor does not affect the conductivity of PN-junction diode:

 
 
 
 

56. The characteristic of transistor are:

 
 
 
 

57. A.C is converted into D.C by

 
 
 
 

58. Which of the followings is not basic operation of Boolean variable

 
 
 
 

59. The process due to which current flows only during alternate half cycle is known as:

 
 
 
 

60. Hole is equivalent to:

 
 
 
 

61. When transistor works as an amplifier, its output is:

 
 
 
 

62. P-n junction when reversed biased acts as a:

 
 
 
 

63. The electronic circuit which gives the inversion of input signal at the output is called

 
 
 
 

64. The input resistance of an op-amplifier is:

 
 
 
 

65. The size of base in a transistor is

 
 
 
 

66. All the valence electrons present in a crystal of silicon are bounded in their orbits by:

 
 
 
 

67. Identify which device used the rectification:                   

 
 
 
 

68. In the transistor schematic symbol, the arrow is:         

 
 
 
 

69. Emitter base junction is always:             

 
 
 
 

70. The width of depletion region of a junction:      

 
 
 
 

71. The barrier potential of Silicon Diode at room temperature is:

 
 
 
 

72. Which one of the following device based on p-n junction:

 
 
 
 

73. When a silicon crystal is doped with a pentavalent element, it becomes

 
 
 
 

74. The automatic working of street lights is due to

 
 
 
 

75. In forward biased situation, as the biasing voltage is increased, the current:

 
 
 
 

76. Minority carries in n-type substances are:                     

 
 
 
 

77. Light emitting diode based on:

 
 
 
 

78. Transistor can be used as:                       

 
 
 
 

79. A photo diode can be used:                     

 
 
 
 

80. PN-junction cannot be used as

 
 
 
 

81. A combination of p-type and N-type substance give rise to:

 
 
 
 

82. Photodiode is operated:               

 
 
 
 

83. At 0 K semi conductors are

 
 
 
 

84. Temperature coefficient of resistivity of a semi conductor is:

 
 
 
 

85. In forward biasing, the value of resistance is

 
 
 
 

86. In p-type substances, the minority carries are:

 
 
 
 

87. Find the gain if inverting, amplifier of external resistance R1 = 10KΩ and r²  = 100K Ω

 
 
 
 

88. The potential difference across depletion region in case of Si is:

 
 
 
 

89. Output resistance of an op-amp is

 
 
 
 

90. Conversion of only one half of A.C. into D.C. is called

 
 
 
 

91. In an n-type semi conductor there are:  

 
 
 
 

92. A NAND gate with two inputs A &B has an out put 0, if

 
 
 
 

93. SI unit of current gain is:

 
 
 
 

94. The semi conductor diode has the property of a:         

 
 
 
 

95. To turn the transistor OFF, the base current is set:

 
 
 
 

96. In general, most of the electrical circuits make use of:

 
 
 
 

97. While drawing a graph between current and biasing voltage in p-n junction, the current is taken:

 
 
 
 

98. The light emitting diode emits light when it is: 

 
 
 
 

99. The number of LEDs required to display all the digits is:

 
 
 
 

100. Photo diode can turn its current on and off in

 
 
 
 

101. An operational amplifier can be used as:           

 
 
 
 

102. The emitter and base has concentration of impurity:

 
 
 
 

103. The basic condition for a transistor amplifier circuit is:

 
 
 
 

104. The potential difference set up across the depletion region
is called

 
 
 
 

105. Semi conductor diode conducts only when it is:          

 
 
 
 

106. The gain of the non-inverting amplifier can be expressed as

 
 
 
 

107. A single photovoltaic cell produces a current of:

 
 
 
 

108. A Potential difference is developed across the depletion region of p-n junction due to:

 
 
 
 

109. Semi conductors with donor atoms and free electrons belong to the type:

 
 
 
 

110. A region having zero charge particle:

 
 
 
 

111. Transistor was discovered by

 
 
 
 

112. A junction between p and n materials forms:    

 
 
 
 

113. The potential barrier for silicon at room temperature is

 
 
 
 

114. The circuit which compares the two voltages is

 
 
 
 

115. The photodiodes are used for:

 
 
 
 

116. Which one can be used as temperature sensor in electric circuit?

 
 
 
 

117. The most commonly used diode for special purpose is:

 
 
 
 

118. The number of terminals in a semiconductor diode is

 
 
 
 

119. Usually VBB is:

 
 
 
 

120. The diode used for the detection of visible and in visible light is:

 
 
 
 

121. A photo diode is a semi conductor diode usually made from

 
 
 
 

122. A transistor has:    

 
 
 
 

123. The magnitude of open loop gain at room temperature is:

 
 
 
 

124. The external potential difference applied to p-n junction for forward biasing supplied energy to:

 
 
 
 

125. The impurity in the germanium is usually in the ratio of:

 
 
 
 

126. There is no current due to holes in good electrical conductors because they have:

 
 
 
 

127. The specially designed semi-conductor used for as fast countings in electronic circuits will be :

 
 
 
 

128. A light emitting diode (LED) emits light only when:

 
 
 
 

129. Depletion region carries

 
 
 
 

130. Photodiode is used for detection of heat

 
 
 
 

131. An operational amplifier will act as inverting amplifier, when the input signal is connected to:

 
 
 
 

132. Operational-amplifier has been discussed as comparator of:

 
 
 
 

133. Forward resistance of p-n junction is:               

 
 
 
 

134. The reverse current through a semi-conductor diode circuit
is due to

 
 
 
 

135. The ratio B in transistor is called:

 
 
 
 

136. The central region of a transistor is called

 
 
 
 

137. The crystal of germinium or silicon in its pure form at room temperature acts as:

 
 
 
 

138. In pn junction, p-type end is basically referred as:

 
 
 
 

139. The process of doping causes the resistivity of semi conductor to:

 
 
 
 

140. Which one of the following has the greatest energy gap:

 
 
 
 

141. Transistors are made from

 
 
 
 

142. Minority carriers in a p-type substances are:                

 
 
 
 

143. A potential barrier of 0.7 volt exist across p-n junction made from:

 
 
 
 

144. A diode, which can turn current ON and OFF in nanosecond is called:

 
 
 
 

145. The color of light emitted by a LED depends on

 
 
 
 

146. Silicon is the most commonly used:

 
 
 
 

147. Electrons present in P-type material due to thermal pair generation are:

 
 
 
 

148. The circuit which changes input signal at the output with a phase shift of 1800 is called

 
 
 
 

149. The operational amplifier is:                    

 
 
 
 

150. A light emitting diode is made from

 
 
 
 

151. Light emitting diodes (LED) are made from semi-conductors:

 
 
 
 

152. Majority charge carries in the P-type region of p-n-junction are:

 
 
 
 

153. In n-p-n transistor, the current flows in the direction from:

 
 
 
 

154. The current gain ratio β of a transistor is given as

 
 
 
 

155. The equation of voltage gain β of an amplifier can be expressed as

 
 
 
 

156. During negative half cycle of A.C then p n Junction offers.

 
 
 
 

157. When a p-n junction is reverse biased , the depletion region is

 
 
 
 

158. A light emitting diode is made from:                             

 
 
 
 

159. For rectification we use

 
 
 
 

160. In reverse biased, the resistance offered by the p-n junction is of the order of:

 
 
 
 

161. Conversion of alternating current into direct current is called:

 
 
 
 

162. The thickness of the base is of the order of:

 
 
 
 

163. An n-type substance is:    

 
 
 
 

164. The transistor in a circuit basically acts as:                  

 
 
 
 

165. The forward current through a semi-conductor diode circuit is due to

 
 
 
 

166. Pulsating output of full wave rectifier can be made smooth by using circuit called:

 
 
 
 

167. A photodiode can turn its current ON and OFF in:

 
 
 
 

168. In semi conductor diode the p-type end is usually referred as

 
 
 
 

169. The advantage of LEDs is:                       

 
 
 
 

170. The magnitude of open loop gain of the operational amplifier is of the order of

 
 
 
 

171. The use of LDR is in the circuit of:

 
 
 
 

172. Which one of the following is not semi conductor: 

 
 
 
 

173. Which one of the following has smallest energy gap:

 
 
 
 

174. Reverse current flows due to

 
 
 
 

Short Questions

1. Define depletion region and biasing?
2. Define forward resistance of the p- n junction?
3. Describe anyone use of semi conductor diode?
4. Describe some important applications of photo diodes?
5. Describe the working principle of a LED?
6. Draw a circuit symbol of n-p-n transistor ?
7. Draw a circuit symbol of p-n-p transistor ?
8. Draw a neat diagram of an op- amp?
9. How does an op – amp act as a comparator?
10. How does the motion of an electron in a n- type substance differ from the motion of holes in a p- type substance?
11. How is a p- n junction formed?
12. How many diodes may be used for half wave rectification ?
13. How may types are of rectifications ?
14. How the conductor’s semi – conductors and insulators can be distinguished by bond theory of solids? Explain.
15. LDR stands for ?
16. Define forward resistance of the p-n junction ?
17. The inputs of a gate are 1 and o. identify the gate if its output is (a) 0 (b) 1?
18. What are important properties of semi conductor?
19. What are in holes in semi – conductor? Explain the electron hole pair generation?
20. What are N – type and p- types substance. Explain them?
21. What are semiconductors?
22. What are the advantages and disadvantages of the transistor over a vacuum tube?
23. What are the essential components required for rectification ?
24. What do LED and LASER stand for?
25. What do photo diodes? Point out their use.
26. What do you mean by forward biasing ?
27. What do you mean by reverse biasing ?
28. What do you understand by output resistance and input resistance of an op- amp?
29. What do you understand by saturation in operational amplifier?
30. What do you understand the electronics as a branch of physics?
31. What is a logic gate ?
32. What is a n-p-n transistor ?
33. What is a p-n junction ?
34. What is a p-n-p transistor ?
35. What is a transistor ?
36. What is an amplifier ?
37. What is an operational amplifier?
38. What is AND gate ?
39. What is biasing ?
40. What is Boolean algebra ?
41. What is depletion region ?
42. What is difference between a half – wave rectification and full wave rectification?
43. What is electronics ?
44. What is exclusive OR gate (XOR) ?
45. What is input resistance ?
46. What is meant by amplitude modulation? Explain how information is carried by electromagnetic wave?
47. What is meant by rectification?
48. What is meant by the current gain of a transistor?
49. What is meant for forwarding and reverse biasing of a semi – conductor diode?
50. What is NAND gate ?
51. What is NOT gate ?
52. What is n-type substance ?
53. What is open loop gain of an operational amplifier ?
54. What is open loop gain of an operational amplifier?
55. What is OR gate ?
56. What is output resistance ?
57. What is P- n junction (or semiconductor diode)?
58. What is p- n junction?
59. What is photovoltaic cell ?
60. What is potential barrier ?
61. What is potential barrier of germanium and silicon?
62. What is p-type substance ?
63. What is rectification?
64. What is solar cell (or photovoltaic cell)? Give its uses.
65. What is temperature? Draw symbols of p – n and n – p –n transistor?
66. What is the biasing requirement of the junction of a transistor? For its normal operation? Explain how these requirements are met in a common emitter amplifier?
67. What is the current gain of a transistor ?
68. What is the effect of forward and reverse biasing of a diode on the width of depletion region?
69. What is the function of a sensor ?
70. What is the net charge on n – type or a p – type substance?
71. What is the principle of virtual ground? Apply it to find the gain of an inverting amplifier?
72. What is the use of a photo diode ?
73. What is the voltage gin of a transistor ?
74. What is voltage gain of a transistor?
75. When a p-n junction is formed ?
76. Why a photo diode is operated in a reverse biased state?
77. Why charge carries are not present in the depletion region?
78. Why is a photo – diode operated in reverse biased state?
79. Why is the base current in a transistor very low ?
80. Why ordinary silicon diode does not emit light?
81. Write down some special kinds of diodes ?
82. Write some important uses of OP- amp?
83. Write some important uses of operational amplifier ?
84. Write the equation of a gain of a non – inverting amplifier?

Long Questions

1. What is p-n junction? Also describe forward biased and reverse biased p-n
2. What is meant by rectification? Explain the action of semi-conductor diode as half wave rectifier.
3. What are the specially designed p-n junction? What are the application of p-n junction?
4. How is it used as an amplifier? Give its circuit diagram. Deduce the relation for its voltage gain.
5. What is transistor? Explain its working.
6. How a transistor is used as a switch?
7. Explain operational amplifier.
8. Draw the circuit diagram of inverting amplifier and label it. Evaluate a relation for its gain.
9. Draw the circuit diagram of non-inverting amplifier and label it. Evaluate a relation for its gain.
10. Write a note on op-amp as a comparator.
11. Explain comparator as a night switch.
12. What is digital system?
13. Describe the fundamental logic gates.
“14. Draw the symbols of logic gates for the following Boolean functions. Write their respective truth labels.
NOR Gate, NAND Gate, Exclusive OR Gate , Exclusive-NOR Gate (XNOR), “
15. The current flowing into the base of a transistor is 100 micro Ampere. Find its collector current Ic. its emitter current Te and the ratio Ic/Ie, if the value of current gain β is 100.

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