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Engineering
137 Views   |  


 A 2V battery is connected across AB as shown in the figure. The value of the current supplied by the battery when in one case battery’s positive terminal is connected to A and in other case when positive terminal of battery is connected to B will respectively be :

 

  • Option 1)

    0.2 A and 0.1 A
     

  • Option 2)

    0.4 A and 0.2 A

  • Option 3)

    0.1 A and 0.2 A

     

  • Option 4)

     0.2 A and 0.4 A

 
As we have learned P -N junction as diode - It is a one way device. It offers a low resistance when forward biased and high resistance when reverse biased. - wherein R = 0, Forward  R  Reverse     In one case  NO current will pass through  I = 2/5 A = 0.4 A  In second case : no current will pass through  I = 2/10 = 0.2 A      Option 1) 0.2 A and 0.1 A   Option 2) 0.4 A and 0.2 A Option...
Engineering
277 Views   |  

In the following, which one of the diodes is reverse  biased?

  • Option 1)

      

  • Option 2)

  • Option 3)

  • Option 4)

 
As we have learnt,   P -N junction as diode - It is a one way device. It offers a low resistance when forward biased and high resistance when reverse biased. - wherein R = 0, Forward  R  Reverse    Correct option is 1 In all other figure, diode is forward biased.     Option 1)    Option 2) Option 3) Option 4)
Engineering
94 Views   |  

Given : A and B are input terminals.

Logic 1 = > 5 V

Logic 0 = < 1 V

Which logic gate operation, the following circuit does ?

 

  • Option 1)

     AND Gate
     

     

  • Option 2)

     OR Gate 

  • Option 3)

    XOR Gate

     

  • Option 4)

    NOR Gate

As we have learned AND Gate - - wherein A and B are input Y is out put    When both inputs  > 5 V  then  When one of the inputs is > 5 V  and other < 1 V we get  When both input are  < 1V Then  Hence               A               B               output                            1               1                     1                           1               0                     0          ...
Engineering
79 Views   |  

 For LED’s to emit light in visible region of electromagnetic light, it should have energy band gap in the range of :   

 

  • Option 1)

      0.1 eV to 0.4 eV  
     

     

  • Option 2)

    0.5 eV to 0.8 eV  
     

  • Option 3)

     0.9 eV to 1.6 eV  
     

  • Option 4)

    1.7 eV to 3.0 eV  

 
As we have learned Photo diode - A special type of photo detector. - wherein By measuring the change in the conductance of the semicondutors one can measure the intensity of the optical signal    For emitting visible light   should lie between 34000  to 7600           Option 1)   0.1 eV to 0.4 eV       Option 2) 0.5 eV to 0.8 eV     Option 3)  0.9 eV to 1.6 eV     Option 4) 1.7 eV to 3.0 eV  
Engineering
223 Views   |  

 An n-p-n transistor has three leads A, B and C. Connecting B and C by moist fingers, A to the positive lead of an ammeter, and C to the negative lead of the ammeter, one finds large deflection. Then, A, B and C refer respectively to :

  • Option 1)

     Emitter, base and collector
     

  • Option 2)

     Base, emitter and collector 

  • Option 3)

    Base, collector and emitter

     

  • Option 4)

    Collector, emitter and base.

 
As we have learned Transistor - Three layered semiconducting device . NPN or PNP - wherein 1.    Emitter is heavily doped 2.    collector is moderately doped . 3.    Base is lightly doped & very thin    In the given situation  A = Base  B = Collector  C = Emitter          Option 1)  Emitter, base and collector   Option 2)  Base, emitter and collector  Option 3) Base, collector and...
Engineering
77 Views   |  

 For a common emitter configuration, if α and β have their usual meanings, the incorrect relationship between α and β is :

  • Option 1)

    \frac{1}{\alpha }= \frac{1}{\beta }+1

  • Option 2)

    \alpha = \frac{\beta }{1-\beta }

  • Option 3)

    \alpha = \frac{\beta }{1+\beta }

  • Option 4)

    \alpha = \frac{\beta ^{2}}{1+\beta^{2} }

 
As we have learnt,   Relation between α and β -   - wherein (current gain )    For common emitter configuration              Option 1) Option 2) Option 3) Option 4)
Engineering
64 Views   |  

Carbon, silicon and germanium have four valence electrons each. At room temperature which one of the following statements is most appropriate ?

  • Option 1)

    The number of free electrons for conduction is significant only in Si and Ge but small in C.

  • Option 2)

    The number of free conduction electrons is significant in C but small in Si and Ge .

  • Option 3)

    The number of free conduction electrons is negligibly small in all the three.

  • Option 4)

    The number of free electrons for conduction is significant in all the three .

 
As we have learnt,   p - type semiconductor - Here the base semiconductor (i.e.pure Si or Ge ) is mixed with tetravalent doping material (e.g. Al ) - wherein 1) nh >>ne 2) There is an acceptor level just above  the valence band .     Semiconductor - Energy gap between valence band and conduction band is less than 3 e.v. - wherein 1) lies between conductor & insulator  2) Both electron and...
Engineering
69 Views   |  

A p-n junction (D)   shown in the figure can act as a rectifier.

An alternating current source (V)  is connected in the circuit. The current (I) in the resistor (R) can be shown by

  • Option 1)

  • Option 2)

  • Option 3)

  • Option 4)

 
As we have learned Half Wave Rectifier - It is the type of rectification in which only one half of the input a.c. is translated into the output . - wherein Frequency of output is same as input a.c.     This circuit represent half wave rectifier  During half time diode is forward biased and hence current will flow through it and for next half time cycle diode is in reverse half biased and hence...
Engineering
94 Views   |  

The reverse biasing in a PN junction diode

  • Option 1)

    Decreases the potential barrier

  • Option 2)

    Increases the potential barrier

  • Option 3)

    Increases the number of minority charge carriers

  • Option 4)

    Increases the number of majority charge carriers
     

 
As we learnt in  P -N junction as diode - It is a one way device. It offers a low resistance when forward biased and high resistance when reverse biased. - wherein R = 0, Forward  R  Reverse    Do to reverse biasing potential barrier increases but it has no effect on number of charge carrier. Option 1) Decreases the potential barrier Incorrect Option 2) Increases the potential...
Engineering
139 Views   |  

The approximate ratio of resistances in the forward and reverse bias of the PN-junction diode is

  • Option 1)

    10^{2}:1

  • Option 2)

    10^{-2}:1

  • Option 3)

    1:10^{-4}

  • Option 4)

    1:10^{4}

 
As we learnt in  P -N junction as diode - It is a one way device. It offers a low resistance when forward biased and high resistance when reverse biased. - wherein R = 0, Forward  R  Reverse    Ratio of forward to reverse bias resistance is of the order of  Option 1) Incorrect Option 2) Incorrect Option 3) Incorrect Option 4) Correct
Engineering
316 Views   |  

PN-junction diode works as an insulator, if connected

  • Option 1)

    To A.C.
     

  • Option 2)

     In forward bias

  • Option 3)

    In reverse bias

  • Option 4)

    None of these

 
As we learnt in  P -N junction as diode - It is a one way device. It offers a low resistance when forward biased and high resistance when reverse biased. - wherein R = 0, Forward  R  Reverse   P N Junction in reverse biased mode offer infinitely large resistance and hence no current flow through it. Hence P N Junction in reverse bias act as an insulator. Option 1) To A.C.   Incorrect Option...
Engineering
133 Views   |  

On increasing the reverse bias to a large value in a PN-junction diode, current.

  • Option 1)

    Increases slowly
     

  • Option 2)

    Remains fixed

  • Option 3)

    Suddenly increases

  • Option 4)

    Decreases slowly

 
As we learnt in  Zener diode - It can operate continuously without being damaged in the region of reverse  biased - wherein 1) It acts as voltage regulator 2) In forward biasing it act as ordinary diode .   On increasing reverse bias to a large value in a PN junction diode,current suddenly increase due to Zener / Avalanche breakdown. Option 1) Increases slowly   Incorrect Option 2) Remains...
Engineering
366 Views   |  

Which of the following statements concerning the depletion zone of an unbiased PN junction is (are) true

  • Option 1)

    The width of the zone is independent of the densities of the dopants (impurities)

  • Option 2)

    The width of the zone is dependent on the densities of the dopants

  • Option 3)

    The electric field in the zone is produced by the ionized dopant atoms

  • Option 4)

    The electric field in the zone is provided by the electrons in the conduction band and the holes in the valence band

 
As learnt in P-N junction - When p type semiconductor is mixed with N - type semiconductor, P-N junction formed   - wherein There is very thin region (of the order of micro meter) called depution region.    Width of depletion region depend on densities of dopants. Both electron and holes are responsible for electric field in depletion zone. Option 1) The width of the zone is independent of...
Engineering
91 Views   |  

When a PN junction diode is reverse biased
 

  • Option 1)

    Electrons and holes are attracted towards each other and move towards the depletion region

  • Option 2)

    Electrons and holes move away from the junction depletion region

  • Option 3)

    Height of the potential barrier decreases

  • Option 4)

    No change in the current takes place

 
Using P-N junction - When p type semiconductor is mixed with N - type semiconductor, P-N junction formed   - wherein There is very thin region (of the order of micro meter) called depution region.    and P -N junction as diode - It is a one way device. It offers a low resistance when forward biased and high resistance when reverse biased. - wherein R = 0, Forward  R  Reverse    When PN...
Engineering
92 Views   |  

What is the current in the circuit shown below

  • Option 1)

    0 \, \, \, amp

  • Option 2)

    10^{-2} \, \, \, amp

  • Option 3)

    1 \, \, \, amp

  • Option 4)

    0.10 \, \, \, amp

 
As learnt in P -N junction as diode - It is a one way device. It offers a low resistance when forward biased and high resistance when reverse biased. - wherein R = 0, Forward  R  Reverse    The given diode is in reverse bias hence no current will flow through the resistor, I = 0 amp Option 1) This option is correct Option 2) This option is incorrect Option 3) This option is...
Engineering
250 Views   |  

Two PN-junctions can be connected in series by three different methods as shown in the figure. If the potential difference in the junctions is the same, then the correct connections will be

 

  • Option 1)

    In the circuit (1) and (2)

  • Option 2)

    In the circuit (2) and (3)

  • Option 3)

    In the circuit (1) and (3)

  • Option 4)

    Only in the circuit (1)

 
As learnt in P -N junction as diode - It is a one way device. It offers a low resistance when forward biased and high resistance when reverse biased. - wherein R = 0, Forward  R  Reverse     In figure 2, both PN junction are forward biased and hence both will offer equal resistance and hence potential difference across the two are equal. In figure 3, both the PN junction are reverse biased...
Engineering
130 Views   |  

The PN junction diode is used as

  • Option 1)

    An amplifier
     

  • Option 2)

     A rectifier
     

  • Option 3)

    An oscillator

     

  • Option 4)

    A modulator

 
  Half Wave Rectifier - It is the type of rectification in which only one half of the input a.c. is translated into the output . - wherein Frequency of output is same as input a.c.     Full wave rectifier - It is type of rectification in which output is obtained for both the halves of a.c. - wherein Frequency of output is double to that of input    PN junction can be used as half wave or full...
Engineering
84 Views   |  

The following truth table corresponds to the logic gate
A 0 0 1 1
B 0 1 0 1
X 0 1 1 0

  • Option 1)

    NAND

  • Option 2)

    OR

  • Option 3)

    AND

  • Option 4)

    XOR

 
  OR gate - Relation between input and output      - wherein A and B are input Y is out put    X or gaH output =  Its truth table is    Option 1) NAND Incorrect option Option 2) OR Incorrect option Option 3) AND Incorrect option Option 4) XOR correct option
Engineering
526 Views   |  

The electrical resistance of depletion layer is large because

  • Option 1)

    It has no charge carriers

  • Option 2)

    It has a large number of charge carriers

  • Option 3)

    It contains electrons as charge carriers

  • Option 4)

    It has holes as charge carriers

 
  P-N junction - When p-type semiconductor is mixed with N-type semiconductor, P-N junction formed   - wherein There is a very thin region (of the order of the micrometre) called deputation region.    Since there is no hole or electron available in depletion region and hence it has a high electric resistance.   Option 1) It has no charge carriers Correct option Option 2) It has a large number...
Engineering
440 Views   |  

The electrical circuit used to get smooth dc output from a rectifier circuit is called

  • Option 1)

    Oscillator

  • Option 2)

    Filter
     

  • Option 3)

    Amplifier

  • Option 4)

    Logic gates

 
  Half Wave Rectifier - It is the type of rectification in which only one half of the input a.c. is translated into the output . - wherein Frequency of output is same as input a.c.     Full wave rectifier - It is type of rectification in which output is obtained for both the halves of a.c. - wherein Frequency of output is double to that of input    Filter is used to smoothen dc output from a...
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