Science (English Medium) Class 12 - CBSE Important Questions

Name the two types of atoms used for doping of Ge/Si.

In an extrinsic semiconductor, the number density of holes is 4 × 10²⁰ m^-3. If the number density of intrinsic carriers is 1.2 × 10¹⁵ m^-3, the number density of electrons in it is ______.

The formation of the depletion region in a p-n junction diode is due to ______.

Draw an energy band diagram for a p-type semiconductor at T > 0 K.

Draw the circuit arrangement for studying V-I characteristics of a p-n junction diode in (i) forward biasing and (ii) reverse biasing. Draw the typical V-I characteristics of a silicon diode.

Define modulation index.

How are side bands produced?

Draw a block diagram of a detector for AM signal and show, using necessary processes and the waveforms, how the original message signal is detected from the input AM wave.

Explain the process of amplitude modulation.

Define the term 'amplitude modulation'

Explain any two factors which justify the need for modulating a low frequency base-band signal.

Draw a schematic sketch showing how amplitude modulated signal is obtained by superposing a modulating signal over a sinusoidal carrier wave.

Explain the term demodulation used in a communication system.

Block diagram of a receiver is shown in the figure:

(a) Identify ‘X’ and ‘Y’.

(b) Write their functions.

In the block diagram of a simple modulator for obtaining an AM signal, shown in the figure, identify the boxes A and B. Write their function.

Distinguish between ‘Analog and Digital signals’.

Which one of the following is a princely state of India that initially resisted joining the Indian Union?

In the given political map of India, four states have been marked as A, B, C, and D. Identify these states on the basis of the information given below and write their correct names in your answer book along with the respective serial number of the information used and the concerned alphabet as per the format that follows:

1. The state to which Raj Kumari Amrit Kaur, Health Minister in Nehru's Cabinet, belonged.
2. The state to which former Congress President. S. Nijalingappa, belonged.
3. The state where Karpoori Thakur was the Chief Minister.
4. The State to which the political party DMK belongs.

Which one of the following countries was NOT a part of the Soviet Union?