Science (English Medium) कक्षा १२ - CBSE Important Questions for Physics

Derive an expression for voltage gain of the amplifier and hence show that the output voltage is in opposite phase with the input voltage.

In the following diagram 'S' is a semiconductor. Would you increase or decrease the value of R to keep the reading of the ammeter A constant when S is heated? Give reason for your answer.

State its any ‘two’ uses of photodiode.

Draw its I – V characteristics of photodiode

A zener diode is fabricated by heavily doping both p- and n- sides of the junction. Explain, why?

Explain briefly with the help of necessary diagrams, the forward biasing of a p-n junction diode. Also draw characteristic curves.

Explain briefly with the help of necessary diagrams, the  reverse biasing of a p-n junction diode. Also draw characteristic curves.

In the following diagram, is the junction diode forward biased or reverse biased ?

Write the functions of the three segments of a transistor.

The figure shows the input waveforms A and B for ‘AND’ gate. Draw the output waveform and write the truth table for this logic gate.

Draw a circuit diagram for studying the input and output characteristics of a n-p-n transistor in common emitter configuration. Using the circuit, explain how input, output characteristics are obtained

Draw logic symbol of an OR gate and write its truth table. 

Describe, with the help of a circuit diagram, the working of a photodiode.

Sunil and his parents were travelling to their village in their car. On the way his mother noticed some grey coloured panels installed on the roof of a low building. She enquired from Sunil what those panels were and Sunil told his mother that those were solar panels.
(a) What were the values displayed by Sunil and his mother? State one value for each.
(b) In what way would the use of solar panels prove to be very useful?
(c) Name the semiconductor device used in solar panels. Briefly explain with the help of a diagram, how this device works

Gautam went for a vacation to the village where his grandmother lived. His grandmother took him to watch 'nautanki' one evening. They noticed a blackbox connected to the mike lying nearby. Gautam's grandmother did not know what that box was. When she asked this question to Gautam, he explained to her that it was an amplifier.
(i) Which values were displayed by the grandmother? How can inculcation of these values in students be promoted?
(ii) What is the function of an amplifier?
(iii) Which basic electronic device is used in the amplifier?

The V − I characteristic of a silicon diode is as shown in the figure. Calculate the resistance of the diode at (i) I = 15 mA and (ii) V= −10 V.

Write briefly the important processes that occur during the formation of p−n junction. With the help of necessary diagrams, explain the term 'barrier potential'.

What is an 'integrated  circuit (I.C.) ?

Distinguish between (i) linear I.C. and (ii) digital I.C.

 Identify the equivalent gate for the following circuit and write its truth table.