Physics Class 12 Sample Question Paper / Model Question Paper – I

OLD EXAM PATTERN: (WITHOUT MCQs)

Grade :     CLASS 12                            Subject: PHYSICS            Marks      :      70 

Time   :     3 hrs.                                                              

General Instructions:                 

    a)    All the questions are compulsory.

    b)    There are 26 questions in total.

    c)    This question paper has five sections: Section A, Section B, Section C, Section D and Section E.

    d)    Section A contains five questions of one mark each. Section B contains five questions of two marks

           each, Section C contains twelve questions of three marks each. Section D contains one value based

           question of four marks and Section E contains three questions of five marks each.

    e)    There is no overall choice. However, an internal choice has been provided in one question of two

           marks. One question of three marks and all the three questions of five marks weightage. You have

           to attempt only one of the choices in such questions.

f) Avagadros number =

g) Boltzmann constant =

1. Define the terms (i)magnetic field intensity and (ii)magnetic permittivity                             1M
2. State the law of radioactive disintegration.                                                                              1M
3. Write the expression for velocity of electron in n^th orbit according to Bohr’s atomic model and explain the terms in it.                                                                                                                        1M
4. Draw a circuit diagram showing pn junction diode in reverse bias.                                         1M
5. Find the de Broglie wavelength of an electron moving with a speed of 20m/s.                       1M
6. A radioactive substance has 6.0×10¹⁸ active nuclei initially. What time is required for the active nuclei of the same substance to become 1×10¹⁸ if its half life is 40s.                               2M
7. Mention the uses of (i) X rays and (ii) UV rays.                                                                      2M
8. Mention the reasons for the following statements.

        i)   Amplitude of modulating signal should be less than that of the carrier wave

ii) Maximum frequency in sky wave propagation should be less than 40MHz.                 2M

9. State any two characteristics of electromagnetic waves.        

OR

         State Faraday’s laws of electromagnetism                                                                              2M

10. State Malus law of polarization.                                                                                              2M
11. Differentiate between different types of magnetic materials.                                                  3M
12. Obtain an expression for torque acting on an electric dipole placed in uniform electric field. Will it experience any net force?                                                                                                  3M
13. Derive the expression for capacitance of combination of three capacitors in parallel.
14. Obtain an expression for drift velocity of electrons in a conductor in terms of relaxation time.                                                                                                                                                           3M
15. How will you convert a galvanometer into a voltmeter? Write the necessary mathematical expression.                                                                                                                                 3M
16. Draw the figure showing atomic spectra of hydrogen atom.                                                   3M
17. Explain the working of zener diode as voltage regulator.                                                       3M
18. Give the truth tables and Symbols of AND, NOR , NAND and NOT Gates                              3M
19. What do you understand by modulation? Explain the need of modulation.                             3M
20. Obtain an expression for magnetic field induction due to a circular loop  by using Biot-Savart law.          

Or

         Explain the working of a step-down transformer.                                                                   3M

21. State and explain Lenz’s law with examples.  What is its significance?                           3M

22. Write the disadvantages and applications of eddy currents.                                                    3M

23. There was a fire accident in a multi-storied building. Bhavya, the supervisor of the building called for fire engine and managed to put-off the fire. But there was a huge loss of property. Bhavya planned to install fire alarms made up of photocells in the building to prevent such accidents.

a)   What values are shown by Bhavya?

b)   What is the principle behind the fire alarms used by her?                                                4M

24. State Gauss’s law of electrostatics. Derive an expression for electric field intensity due to a charged conducting sphere and draw the corresponding graph.                                                                                              

Or

 25. Explain the principle of potentiometer. Describe an experiment for the comparison of emf’s of two cells using potentiometer.                                                                                     5M

Derive impedance expression and explain resonance and sharpness of resonance in LCR circuit.

Or

         Explain the construction and working of a moving coil galvanometer                         5M

26. a)     Explain the construction and working of reflecting telescope. What are its advantages over

      refracting telescope?         

Or

         b)    Give the theory of YDSE and derive the conditions for maximum and minimum intensities                                                                                                                                                             5M

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