CBSE Class 12 Physics Delhi Question Paper 2013 (2)

CBSE Class 12 Physics Delhi Question Paper 2013 (2). Students can download the last year question papers using the link below. Free download of examination question papers with solutions.Last 10 year question papers should be practised to get better marks in examinations.

1. Define 'electric line of force' and give its two important properties. 

2. A heating element using nichrome connected to a 230 V supply draws an intial current of 3.2 A which settles after a few seconds at a steady value of 2.8 A. What is the steady temperature of the heating element if the room temperature is 27° C ? Temperature coefficient of resistance of nichrome averaged over the temperature range involved is 1.7×10^-4 °C. 

3. An electric dipole is held in a uniform electric field. (i) Using suitable diagram, show that it does not undergo any translatory motion, and (ii) derive an expression for the torque acting on it and specify its direction. 

4. Explain, with the help of diagram, the principle and working of an a.c. generator. Write the expression for the e.m.f. generated in the coil in terms of its speed of rotation. 

5. Define the term 'resistivity' and write its S.I. unit. Derive the expression for the resistivity of a conductor in terms of number density of free electrons and relaxation time. 

                                                              OR

State the principle of potentiometer. Draw a circuit diagram used to compare the e.m.f. of two primary cells. Write the formula used. How can the sensitivity of a potentiometer be increased ?

6. A converging lens has a focal length of 20 cm in air. It is made of material of refractive index 1.6. If it is immersed in a liquid of refractive index 1.3, what will be its new focal length ? How does the nature of the lens change if this lens is immersed in a liquid of refractive index 1.8 ? 

7. Explain the following terms :

(i) Ground waves

(ii) Space waves

(iii) Sky waves 

8. (a) Draw a graph showing the variation of potential energy of a pair of nucleons as a function of their separation. Indicate the regions in which nuclear force is (i) attractive, and (ii) repulsive.

    (b) Write two characteristic features of nuclear force which distinguish it from the coluomb force. 3

9. Explain, with the help of a circuit diagram, how the thickness of depletion layer in a p-n junction diode charges when it is forward biased. In the following circuit which one of the two diodes is forward biased and which is reverse biased ?

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