CLASS - XII PHYSICS (Unit –Solid and Semiconductor devices & Communication Devices)

1 Give the ratio of number of holes and the number of conduction electrons in an intrinsic semiconductor. [1]

2 Under what condition does a junction diode work as open switch? [1]

3 If the output of a 2-input NAND gate is fed as the input to a NOT gate (i) name the new logic gate obtained and (ii) write down its truth table? [1]

4 Name the type of the communication system in which the signal is discrete and binary coded version of message or information? [1]

5 What type of modulation is used for commercial broadcast of voice signal? [1]

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7 What do you mean by depletion region and potential barrier in junction diode? [2]

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10 Sky has no limit but sky wave propagation has its limit. Explain why? [2]

11 With the help of a labeled circuit diagram, explain full wave rectfication using function diode. Draw input and output wave forms. [3]

12 With the help of a diagram, show the biasing of a light emitting diode (LED). Give its two advantages over conventional incandescent lamps? [3]

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23 Teacher said that it is difficult to install the electric polls in the hilly stations as the surface is not flat. Then a student asked the teacher how the people are able to maintain their lives at night. The teacher while explaining took the name of an optoelectronic device.What values the student has shown?Name the devise that was used to clarify the doubt raised by the student?

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24 i) Draw a circuit diagram to study the input and output characteristics of an n-p-n transistor in its common emitter configuration. Draw the typical input and output characteristics.ii) Explain with the help of a circuit diagram, the working of n-p-n transistor as a common emitter amplifer.

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25 a) Explain the formation of depletion layer and barrier potential in a p-n junctionb) With the help of a labeled circuit diagram explain the use of ap-n junction diode as a full wave rectifier. Draw the input and output waveforms.

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26 a) Draw I-V characteristics of a Zener Diode.b) Explain with the help of a circuit diagram, the use of a Zener Diode as a voltage regulator.c) A photodiode is operated under reverse bias although in the forward bias the current is known to be more than the current in the reverse bias. Explain, giving reasons.

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