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12th Standard Physics English Medium Electronics and Communication Systems Reduced Syllabus Important Questions 2021

12th Standard

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Physics

Time : 01:00:00 Hrs
Total Marks : 105
    Multiple Choice Questions
    15 x 1 = 15
  1. The output transducer of the communication system converts the radio signal into ________.

    (a)

    Sound

    (b)

    Mechanical energy

    (c)

    Kinetic energy

    (d)

    None of the above

  2. Which of the following is not the advantage of PN junction diode over tube value?

    (a)

    Unlimited life

    (b)

    No warming-up time after switching

    (c)

    Large efficiency

    (d)

    Low consumption of power

  3. In a N-P-N transistor circuit, the emitter, collector and base current are respectively IE, IC and lB. The relation between them is

    (a)

    ICEB

    (b)

    IBCE

    (c)

    IB>IC>IE

    (d)

    IB>IC>IE

  4. From the follwoing semi-conductor devices _________ operates in forward bias only.

    (a)

    varactar diode

    (b)

    zener diode

    (c)

    light emitting diode

    (d)

    photo-diode

  5. To obtain a p-type germanium semiconductor, it must be doped with

    (a)

    Indium

    (b)

    phosphorus

    (c)

    arsenic

    (d)

    antimony

  6. The radiation of electrical energy is practicable only above _________

    (a)

    20 kHz

    (b)

    200 MHz

    (c)

    200 kHz

    (d)

    20 Hz

  7. The energy band gap is maximum in

    (a)

    metals

    (b)

    insulators

    (c)

    semiconductor

    (d)

    superconductors

  8. If the distance between the conduction band and valence band is leV, then this combination is

    (a)

    semiconductor

    (b)

    metal

    (c)

    insulator

    (d)

    conductor

  9. Resistance of a semiconductor is ______ to temperature change.

    (a)

    directly proportional

    (b)

    indirectly proportional.

    (c)

    a constant

    (d)

    independent

  10. Pure semiconductors are called _________

    (a)

    extrinsic semiconductor

    (b)

    intrinsic semiconductor

    (c)

    simple semiconductor

    (d)

    charged semiconductor

  11. Doped semiconductors are ____________

    (a)

    extrinsic

    (b)

    intrinsic

    (c)

    simple

    (d)

    charged

  12. To remove d.c. voltage fluctuations we use _______

    (a)

    filter circuits

    (b)

    sieve circuits

    (c)

    conductor circuits

    (d)

    rectifier circuits

  13. In PNP transistors, the direction of conventional current, when emitter-base junction is forward-biased is from __________

    (a)

    base to emitter

    (b)

    emitter to base

    (c)

    collector to base

    (d)

    base to collector

  14. ln NPN transistors, when the emitter-base junction is forward-biased, the direction of conventional current is from _____________

    (a)

    base to emitter

    (b)

    emitter to base

    (c)

    collector to base 

    (d)

    base to collector

  15. Qutput characteristics of an NPN, transistor in CE mode is drawn between ___________

    (a)

    IC and VBE

    (b)

    IE and VCE

    (c)

    IB and VCE

    (d)

    IC and VCE

  16. 2 Marks
    10 x 2 = 20
  17. Define electron motion in a semiconductor.

  18. Distinguish between Intrinsic and extrinsic semiconductors.

  19. Discuss the biasing polarities in an NPN and PNP transistors

  20. What is the phase relationship between the AC input and output voltages in a common emitter amplifier? What is the reason for the phase reversal?

  21. Give circuit symbol, logical operation, truth table, and Boolean expression of AND, OR, NOT, NAND, NOR, and EX-OR gates

  22. Define energy band

  23. Define Reverse bias.

  24. Define Zener effect

  25. Write the demerits of fiber optic communication?

  26. What is mobile communication?

  27. 3 Marks
    10 x 3 = 30
  28. Elucidate the formation of a N -type and P-type semiconductors.

  29. Explain the formation of PN junction diode. Discuss its V-I characteristics.

  30. Write notes on Photodiode

  31. State Boolean laws. Elucidate how they are used to simplify Boolean expressions with suitable example.

  32. State and prove De Morgan's First and Second theorems.

  33. Determine the wavelength of light emitted from LED which is made up of GaAsP semiconductor whose forbidden energy gap is 1.875 eV. Mention the colour of the light emitted (Take h = 6.6 × 10-34 Js).

  34. Give the Schematic representation of valence band, conduction band, and forbidden energy gap. and draw energy band structure of
    (a) Insulators
    (b) Semiconductors
    (c) Metals?

  35. What are the advantages of FM

  36. Write the application of satellite communication.

  37. Why ground wave cannot be used for long distance communication using high frequency?

  38. 5 Marks
    8 x 5 = 40
  39. The given circuit has two ideal diodes connected as shown in figure below. Calculate the current flowing through the resistance R1

  40. In the circuit shown in the figure, the input voltage Vi is 20 V, VBE = 0 V and VCE = 0 V. What are the values of IB, IC, β?

  41. Calculate the range of the variable capacitor that is to be used in a tuned-collector oscillator which has a fixed inductance of 150 μH. The frequency band is from 500 kHz to 1500 kHz.

  42. What is the output Y in the following circuit, when all the three inputs A, B, and C are first 0 and then 1?

  43. In the combination of the following gates, write the Boolean equation for output Y in terms of inputs A and B.

  44. Explain and classify transistor as an oscillator.

  45. Write any two distinguishing features between Insulators, Metals and semiconductors and. insulators an the basis of energy band diagrams.

  46. Write the applications of mobile communication.

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