Science (English Medium) इयत्ता १२ - CBSE Important Questions

Distinguish between a metal and an insulator on the basis of energy band diagrams ?

Why is zener diode fabricated by heavily doping both p- and n-sides of the junction?

Draw the circuit diagram of zener diode as a voltage regulator and briefly explains its working ?

How is a photodiode fabricated?

Briefly explain its working. Draw its V - I characteristics for two different intensities of illumination ?

In the circuit shown in the figure, identify the equivalent gate of the circuit and make its truth table.

Describe briefly with the help of a circuit diagram, how the flow of current carriers in a p-n-p transistor is regulated with emitter-base junction forward biased and base-collector junction reverse biased.

Name the device which is used as a voltage regulator. Draw the necessary circuit diagram and explain its working?

Explain briefly the principle on which a transistor-amplifier works as an oscillator. Draw the necessary circuit diagram and explain its working ?

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

Write two characteristic features to distinguish between n-type and p-type semiconductors ?

How does a light emitting diode (LED) work? Give two advantages of LED’s over the conventional incandescent lamps.

Draw the circuit for studying the input and output characteristics of and transistor in CE configuration. Show, how, from the output characteristics, the information about the current amplification factor (β_ac) can obtained.

Draw a plot of the transfer characteristics (V₀ versus V_i) for a base-biased transistor in CE configuration. Show for which regions in the plot, the transistor can operate as a switch ?

Why is a zener diode considered as a special purpose semiconductor diode?

Draw the I − V characteristics of zener diode and explain briefly how reverse current suddenly increase at the breakdown voltage.

Describe briefly with the help of a circuit diagram how a zener diode works to obtain a constant dc voltage from the unregulated dc output of a rectifier ?

The output of an OR gate is connected to both the inputs of a NAND gate Draw the logic circuit of this combinaion of getes and write its truth table.

(i) Write the truth tables of the logic gates marked P and Q in the given circuit.
(ii) Write the truth table for the circuit. 

Why are NOR gates considered as universal gates?