PHYSICS (Set I— Compartment Delhi)
Q. 1. Name the type of radio wave propagation involved when TV signals, broadcast by a tall antenna, are intercepted directly by the receiver antenna.1
Q. 2. Define work function for a given metallic surface. 1
Q. 3. A nucleus, of mass number at has a mass defect . Give the formula, for the binding energy per nucleon, of this nucleus. 1
Q. 4. Which of the two main parts of an optical fibre has a higher value of refractive index? 1
Q. 5. The distance, of the field point, on the equatorial plane of a small electric dipole, is halved. By what factor will the electric field, due to the dipole change? 1
Q. 6. You are given a low resistance R1, a high resistance R2 and a moving coil galvanometer. Suggest how you would use these to have an instrument that will be able to measure (i) currents, (ii) potential differences. 2
Q. 7. A coil of inductance, L, a capacitor of capacitance, C, and a resistor of resistance R, are all put in series with an alternating source of emf
Write an expression for the
Q. 8. Plot a graph to show the variation of the angle of deviation as a function of angle of Incidence for light rays passing through a prism.
Q. 9. The flux of the electrostatic field, through the closed spherical surface S’, is found to be four times that through the closed spherical surface S. Find the magnitude of the charge 2
Q. 10. When the cold junction, of an aluminium-lead thermocouple, is maintained at 00C the thermo emf, E, of this thermocouple, has the temperature dependence given by the relation
Q. 11. .A plane electromagnetic wave travels, in vacuum, along the y-direction. Write the (i) ratio of the magnitudes, and (ii) the directions of its electric and magnetic field vectors. 2
Q. 12. Which special type of diode can act as a voltage regulator? Give the symbol of this diode and draw the general shape of its V — I characteristics. 2
Name the p-n junction diodes which emit spontaneous radiation when forward biased. How do we choose the semiconductor, to be used in these diodes, if the emitted radiation, is to be in the visible region? 2
Q.13. Give the symbol, and the truth table, of each of the two logic gates, obtained by using the two circuits, shown below. 3
Q. 14. Explain briefly with the help of diagrams, the terms: (i) amplitude modulation, (ii) frequency modulation. Which of these (a) gives better quality transmission, (b) has a larger coverage? 3
Q. 15. In the given network, find the values of the currents, I1, I2 and I3. 3
Q. 16. In a potentiometer, a standard cell of emf 5 V and of negligible resistance maintains a steady current through the potentiometer wire of length 5 m. Two primary cells of emf E1 and E2 are joined in series with (i) same polarity, and (ii) opposite polarity. The combination is connected through a galvanometer and a jockey to the potentiometer. The balancing lengths in the two cases are found to be 350 cm and 50 cm respectively.
Q. 17. A long solenoid with closely wound turns has a turns, per unit of its length. A steady current I flows through this solenoid. Use Ampere’s circuital law to obtain an expression, for the magnetic field, at a point on its axis and close to its mid point. 3
Q. 18. Two similar bars made from two different materials P and Q, are placed, one-by-one, in a non-uniform magnetic field. It is observed that
Q. 19. Show diagrammatically two different arrangements used for winding the primary and secondary coils in a transformer.
Q. 20. Show that a convex lens produces an N times magnified image when the object distances, from the lens, have magnitudes
Here f is the magnitude of the focal length of the lens.
Q. 21. Obtain the expression for the wavelength of de Brogue wave associated with an electron accelerated from rest through a potential difference V.
Q. 22. (a) In the working of a transistor, emitter-base (ER) junction is forward biased while collector-base (CB) junction is reverse biased. Why?
Q. 23. An optical communication system, having an operating wavelength, (in metres) can use only x% of its source frequency as its channel bandwith. The system is to be used for transmitting TV signals requiring a bandwidth of F hertz. How many channels can this system transmit simultaneously?
Q. 24. A rectangular conductor, LMNO, Is placed in a uniform magnetic field
directed perpendicular to the plane of the conductor (as shown in the fig.). Obtain an expression, for the emf induced in the arm MN, when the arm is moved towards the left with a speed v.
Q. 25. (a) Define the term ‘electrostatic potential’.
Q. 26. Explain the phenomenon of diffraction of light at a single slit, to show the formation of diffraction fringes. Show graphically the variation of the Intensity, with angle, in this single slit diffraction pattern. What is meant by the term ‘angular resolution’ of a telescope? 5
Which special characteristic of light is demonstrated only by the phenomenon of polarisation? Distinguish clearly between linearly polarized light and unpolarized light.
Q. 27. Explain how radioactive nuclei can emit
even though atomic nuclei do not contain these particles. Hence explain why the mass number of a radioactive nuclide does not change during