pn junction diode mcq

Important Question- Answers of Semiconductor Diode

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MCQ on Semiconductor

 1. Which of the following is not an active component

          A. SCR                   

          B. DIODE

          C. RESISTOR         


               Ans = C 

  2. Energy gap of a non-conductor is

          A. Complete overlapped           

          B.very small and vacant

          C. Very large and vacant          

          D.  none of these

           Ans = C

 3. A semiconductor is formed by……….. Bonds

         A. Covalent             

         B. Electrovalent

         C. Co-ordinate         

         D.  Ionic

         Ans = A

 4. A semiconductor has ……….Temperature Coefficient of resistance

         A. Positive                  B. Zero

         C. Negative                D.  NOT

         Ans = C  (Conductor- +ve, Semiconductor – _ve, Insulator –ve)

         Negative Coefficient Means When increase the temperature then the resistance will decrease

 5. Barrier potential in silicon diode

         A. 0.72eV             B. 1.12eV

         C. 0.15eV             D. 1.72eV

          Ans = B      ( For Ge Diode 0.72eV)

 6. Valance electron in a semiconductor

         A. 2                 B. 4  

         C. 8                 D.  6

         Ans = B

 7. When a Pentavalent impurity is added to a pure semiconductor, it becomes

        A. An insulator                           

        B. An intrinsic semiconductor

        C. P-type semiconductor           

        D. N-type semiconductor

        Ans = D

 8. Atomic no of Germanium

         A. 32             B. 14  

         C. 29             D. 16

         Ans = B

 9. As the doping to a pure semiconductor increases, the bulk resistance of the semiconductor

         A. Remains the same

         B. Increases

         C. Decreases       

         D. None of the above

         Ans = C

 10. Which are responsible of Current flow in a semiconductor

         A. Only free electron                     

         B. only holes

         C. Holes and free electrons         

         D. both

         Ans = C

 11. Semiconductors in ure forms known as

          A. Intrinsic              B.Extrinsic

          Ans = A

 12. How many valance electrons in a Pentavalent impurity?

          A. 3                    B. 5

          C. 4                    D. 6

          Ans = B

 13. Which of the following is Impurity material of valency 3

          A. Boron               

          B. Arsenic

          C. Bismuth           

          D. Phosphorus

           Ans =A   , (Indium, Boron, Gallium has 3) Arsenic Bismuth and phosphorus has 5)

 14. Which is impurity for an N-type material

           A. Silicon                B. Antimony

           C. Gallium              D. Boron

            Ans = A

 15. In a semiconductor, Current conduction due to

            A. Only holes                         

            B. Only free electrons

            C. Holes and free electrons   

            D.  None of the these

            Ans = C

 16. Which type of charge on P-type material

            A. Positive               B. Negative

            C. Neutral                D. None of these 

            Ans = A

 17. Majority carrier in N-type material

            A. Electron                B. Holes

            C. Both A and B        D. None these

            Ans = A

 18. Most commonly used Rectifier is

             A. Half wave rectifier

             B. Full wave  bridge rectifier

             C. Center-tap full wave rectifier

             D. None of these

             Ans = B

 19. The diode is Which type of component

             A. One directional  OR Unidirectional   

             B. Bidirectional

             C. Tridirectional        D. None of these 

             Ans = A

 20. How many junctions is in a diode

             A. 2

             B. 3

               C. both

             Ans =  A

 21. Resistance in a diode in Forward bias is

             A. Low             B.  Zero

             C. High            D. Very high

              Ans = A

 23. Reverse Breakdown voltage that is Fixed already in diode

              A. Zener breakdown               

              B. Avalanche breakdown

              C. A and B                             

              D. None of these 

               Ans = A

 24. The width of depletion layer in Reverse bias

               A. Increase                   

               B. Decrease

               C. Constant                 

               D. None of these 

                Ans = A

 25. Ripple frequency of a half-wave rectifier is

            A. Equal to input              B. Double of input

            C. Half of input                 D. 4 times of input

             Ans = A

 26. Output frequency of a full wave rectifier is 50 hz, What is input frequency

             A. 100hz               B. 200hz

             C. 50hz                 D. 25hz

              Ans = D

 27. Input frequency of a 3-phase half wave rectifier is 50hz, then output frequency is

              A. 150hz            B. 25hz

              C. 300hz            D. 50hz

               Ans = A

 28. A half-wave rectifier is connected with input of 24V 50hz AC, What is Output DC voltage?

               A. 12v           B.  9.9v

               C. 10.8v        D.   5.4v

            Ans = C (formula 0.45xVrms=0.45x 24= 10.8)

 29. What is formula for calculate the output DC voltage of Full Wave Bridge rectifier ?

             A. 0.45x Vrms          B. 0.90x Vrms

             C. 0.50x Vrms          D. 0.8x Vrms

             Ans= B

 30. What is the ripple factor of half-wave rectifier?

              A. 0.48         B. 1.11

              C. 1.21         D.   0.81

              Ans = C   ( for full wave 0.48)

 31. How many diode in Center-tap Full wave rectifier

              A. 2           

              B. 1

              C. 6

              Ans = A

 32. What is the efficiency of a full-wave rectifier

             A. 10.6%       B. 1.6%

             C. 81.2%       D. 100%

          Ans = C  (10.6% in half-wave rectifier)

 33. What should The Current Rating of the diode in a bridge rectifier?

             A. Half of load current     

             B. Equal to Load Current

             C. Double of Load current 

             Ans = A   ( B in half wave rectifier)

 34. A Zener diode is Always connected in

            A. Forward Bias       B. Reverse Bias

             Ans= B

 35. What is the work of a Zener Diode ?

         A. Constant current, constant voltage     

         B. constant current, Varied voltage

         C. Varied current, Constant voltage       

         D. Varied current, Varied Voltage

          Ans = C

 36. A PN junction semiconductor diode is most suitable for the purpose of

        A. Converter

        B. Amplifier

        C. Rectifier

        D. Transistor

         Ans = C

 37. Which type of diode is work as a Variable Capacitor?

         A. Tunnel Diode     B. LED

         C. Varactor Diode      D.Photo diode

          Ans = C

 38. What is the breakdown voltage of LED?

         A. 0.1V-0.3V     

         B. 1.7V- 3.0V

         C. 5.0V- 7.5V     

         D. 10.2V- 20.5V

          Ans = B

 39. The conductivity of a semiconductor ……… adding impurity

           A. Increase      B. Decrease

           C. Both            D. None of these

          Ans = A

 40. If there is no Filter capacitor connected in the Output of the Rectifier Circuit, What happen?

           A. Low signal interference , high noise

           B. High signal interference, Low noise

           C. High Signal interference, High Noise

           D. Low signal interference, low noise

          Ans = C

 41. What is the purpose of the capacitor in a filter circuit?

           A. Remove ripple from Rectified Output

           B. Increase Output Dc  Voltage

           C. To decrease the variation of input AC

             Ans = A

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