PUC Science 2nd PUC Class 12 - Karnataka Board PUC Question Bank Solutions

A particular particle created in a nuclear reactor leaves a 1 cm track before decaying. Assuming that the particle moved at 0.995c, calculate the life of the particle (a) in the lab frame and (b) in the frame of the particle.

Why does current in a steady state not flow in a capacitor connected across a battery? However momentary current does flow during charging or discharging of the capacitor. Explain. 

How is amplitude modulation achieved?

The frequencies of two side bands in an AM wave are 640 kHz and 660 kHz respectively. Find the frequencies of carrier and modulating signal. What is the bandwidth required for amplitude modulation?

Write the two processes that take place in the formation of a p-n junction.

(i) Find the value of the phase difference between the current and the voltage in the series LCR circuit shown below. Which one leads in phase : current or voltage ?

(ii) Without making any other change, find the value of the additional capacitor C₁, to be connected in parallel with the capacitor C, in order to make the power factor of the circuit unity.

Define the term 'amplitude modulation'

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

Find the wavelength of the electron orbiting in the first excited state in hydrogen atom.

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.

A series LCR circuit is connected to a source having voltage v = v_m sin ωt. Derive the expression for the instantaneous current I and its phase relationship to the applied voltage.

Obtain the condition for resonance to occur. Define ‘power factor’. State the conditions under which it is (i) maximum and (ii) minimum.

What type of wavefront will emerge from a (i) point source, and (ii) distance light source?

What is meant by term ‘modulation’? Draw a block diagram of a simple modulator for obtaining an AM signal.

 Derive an expression for the average power consumed in a series LCR circuit connected to a.c. source in which the phase difference between the voltage and the current in the circuit is Φ.

Draw a circuit diagram to study the input and output characteristics of an n-p-n transistor in its common emitter configuration. Draw the typical input and output characteristics.

Explain, with the help of a circuit diagram, the working of n-p-n transistor as a common emitter amplifier.

How is a zener diode fabricated so as to make it a special purpose diode? Draw I-V characteristics of zener diode and explain the significance of breakdown voltage.

Explain briefly, with the help of a circuit diagram, how a p-n junction diode works as a half wave rectifier.

Why should the material used for making permanent magnets have high coercivity?