Q. 1. Sketch two equipotential surfaces for a point charge.

Q. 2. If the length of a wire conductor is doubled by stretching it, keeping the p.d. across it constant, by what factor does the drift speed of electrons change?

 

Q. 3. Give two factors on which the temperature of inversion of a thermocouple depends.

 

Q. 4. The current through the wire PQ is increasing. In which direction does the induced current flow in the closed loop?

Q. 5. What is the range of frequencies used for TV transmission?

 

Q. 6. Sketch the refracted wave front emerging from a convex lens, if a plane wave front is incident normally on it.

 

Q. 7. Why do magnetic lines of force prefer to pass through fer¬romagnetic substances than through air?

 

Q. 8. Two stars A and B have their magnitudes - 3 and + 5 respec¬tively. Which star looks brighter?

 

Q. 9. (i) Calculate the electric potential at a point X due to a charge of 0.5 μC located at 10 cm from it.
(ii) Also calculate the work done in bringing a charge of 3 x 10^-9 C from infinity to the point X.

 

Q. 10. Draw a labelled diagram of a Lechlanche cell. How is polarisation overcome in this cell?

 

ver voltameter can be used to check the accuracy of an ammeter.

 

Q. 12. How are eddy currents produced? Mention two applications of eddy currents.

 

Q. 13. In a plane electromagnetic wave, the electric field oscillates with a frequency of 2 x 10¹⁰ s^-1 and an amplitude of 40 V/m.
(i) What is the wavelength of the wave, and
(ii) What is the energy density due to the electric field?

 

Q. 14. The aperture of the objective lens of an astronomical telescope is doubled. How does it affect
(i) the resolving power of the telescope, and (ii) the intensity of the image ?

 

Q. 15. An illuminance of 2 x 10⁵ lumen/m² is produced by sunlight incident normally on the surface of the earth. Calculate the luminous flux of the sun, if it is at a mean distance of 1.5 x 10¹¹ m from the earth.

 

Q. 16. What is an ideal diode? Draw the output wave form across the load resistance R, if the input wave form is as shown in the figure.

 

Q. 17. The activity of a radioactive element drops to 1/16th of its initial, value in 32 years. Find the mean life of the sample.

 

 

Q. 18. Describe how the distance of an inferior planet from the sun can be determined?

 

Q. 19. Define resistivity of a substance. Give its unit. How does it vary with temperature in
(i) good conductors,
(ii) ionic conductors, and
(iii) semiconductors?

 

Q. 20. How will you use a meter bridge to measure an unknown resistance? Draw the necessary circuit diagram. Explain the principle of the experiment. Give the formula used.

 

Q. 21. Explain how you will convert a galvanometer into a voltmeter to read a maximum potential of ‘V’ volts. Can one use a voltmeter to measure the e.m.f. of a cell? Justify your .

 

Q. 22. How does the angle of dip vary as one moves from the Equator towards the North Pole? If the horizontal component of earth’s magnetic field at a place where the angle of dip is 60° is 0.4 x 10^-4 tesla, calculate the vertical component and the resultant magnetic field of earth at that point.

 

 

Q. 23. Derive the expression for the fringe width in Young’s double slit experiment, for a monochromatic source of light.

 

Q. 24. A compound lens is made of two lenses in contact having powers + 12.5 D and - 2.5 D. An object is placed at 15 cm from this compound lens. Find the position and nature of the image formed.

 

Q. 25. Draw a labelled diagram of Millikan’s oil drop experiment. Discuss the principle involved in the determination of the electronic charge.

 

Q. 26. The output of a 2-input AND gate is fed to a NOT gate. Draw the logic circuit of the combination and write down the truth table. Identify the new logic gate formed.

 

Q. 27. Draw a circuit diagram to show the biasing of an n-p-n transistor. Explain the transistor action.

 

 

Q. 28. Prove that an ideal capacitor does not dissipate power in an a.c. circuit.
Find the inductance of the inductor used in series with a bulb of resistance 10 ohm connected to an a.c source of 80 V, 50 Hz. The power factor of the circuit is 0.5. Also, calculate the power dissipation in the circuit.

 

Q. 29. Explain the principle, construction and working of a Van de Graff generator.

 

Or

 

Derive the expression for the capacitance of a parallel plate capacitor when the space between the plates is partially filled with a dielectric medium of dielectric constant ‘K’ Explain why the capacitance decreases when the dielectric medium is removed from between the plates.

 

Q. 30. State Bohr’s postulates for hydrogen atom.

The wavelength of the first spectral line of Balmer series in hydrogen spectrum is 6560 A. Calculate the wavelength of the 2nd spectral line of Lyman series, lonisation energy of hydrogen atom is 13.6 eV.