Science (English Medium) कक्षा १२ - CBSE Question Bank Solutions

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

How is a photodiode fabricated?

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

A flexible wire of irregular shape, abcd, as shown in the figure, turns into a circular shape when placed in a region of magnetic field which is directed normal to the plane of the loop away from the reader. Predict the direction of the induced current in the wire.

A proton and a deuteron having equal momenta enter in a region of a uniform magnetic field at right angle to the direction of a the field. Depict their trajectories in the field.

A capacitor, made of two parallel plates each of plate area A and separation d, is being charged by an external ac source. Show that the displacement current inside the capacitor is the same as the current charging the capacitor. 

Draw V − I characteristics of a p-n junction diode. Answer the following questions, giving reasons:

(i) Why is the current under reverse bias almost independent of the applied potential up to a critical voltage?

(ii) Why does the reverse current show a sudden increase at the critical voltage?

Name any semiconductor device which operates under the reverse bias in the breakdown region.

The current in the forward bias is known to be more (~mA) than the current in the reverse bias (~μA). What is the reason, then, to operate the photodiode in reverse bias?

Draw the circuit diagram of a full wave rectifier using p-n junction diode.

Explain its working and show the output, input waveforms.

Show the output waveforms (Y) for the following inputs A and B of (i) OR gate (ii) NAND gate ?

Describe briefly, with the help of a diagram, the role of the two important processes involved in the formation of a p-n junction.

Write the expression for the force,`vecF` acting on a charged particle of charge ‘q’, moving with a velocity `vecV` in the presence of both electric field `vecF`and magnetic field `vecB` . Obtain the condition under which the particle moves undeflected through the fields.

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

When the width of the slit is made double, how would this affect the size and intensity of the central diffraction band? Justify.

What happens to the width of depletion player of a p-n junction when it is (i) forward biased, (ii) reverse biased?

Net capacitance of three identical capacitors in series is 2 μF. What will be their net capacitance if connected in parallel?

Write the expression for Lorentz magnetic force on a particle of charge ‘q’ moving with velocity `vecv` in a magnetic field`vecB`. Show that no work is done by this force on the charged particle.

A parallel plate capacitor is being charged by a time varying current. Explain briefly how Ampere’s circuital law is generalized to incorporate the effect due to the displacement current ?

Draw the circuit diagram of an illuminated photodiode in reverse bias. How is photodiode used to measure light intensity?

Explain the formation of depletion layer and potential barrier in a p−n junction.