Science (English Medium) Class 12 - CBSE Important Questions for Physics

Draw a circuit diagram of a p-n-p transistor and explain how it works as a transistor amplifier

Write clearly, why in the case of a transistor (i) the base is thin and lightly doped

Write clearly, why in the case of a transistor (ii) the emitter is heavily doped.

What causes the setting up of high electric field even for small reverse bias voltage across the diode?

If a small voltage is applied to a p-n junction diode, how will the barrier potential be affected when it is (i) forward biased

If a small voltage is applied to a p-n junction diode, how will the barrier potential be affected when it is(ii) reveres biased?

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