Q 1. Give two factors by which voltage sensitivity of a moving coil galvanometer can be increased. 

	Q 2. How does the maximum kinetic energy of electrons emitted vary with the work function of the metal? 

	Q 3. How does the frequency of a beam of ultraviolet light change when it goes from air into glass? 

	Q 4. How is the luminosity of a star related to its surface temperature?
	
	Q 5. Why is the heavy water used as moderator in a nuclear reactor?

	Q 6. What is the power dissipation in an a.c. circuit in which voltage and current are given by:

	        V = 300 sin (?t + p/2) and I = 5 sin ?t ?

	Q 7. Draw the graph showing the variation of intensity of polarised light transmitted by an analyser.

	Q 8. Give two defects of a voltaic cell.

	Q 9. Define 'intensity of magnetisation' of a magnetic material. How does it vary with temperature for a paramagnetic 
	       material?

	Q 10. A bar magnet of magnetic moment M is aligned parallel to the direction of a uniform magnetic field B. What is 
	         the work done, to turn the magnet, so as to align its magnetic moment:

	         (i) opposite to the field direction and 
	         (ii) normal to the field direction?

	Q 11. Calculate the solar constant on a planet which is approximately 5 A.U. from the sun. Assume the solar constant 
	         on earth as 1400 W/m2.

	Q 12. Red light is incident on a thin converging lens of focal length 'f'. Briefly explain how the focal length of the lens will 
	         change, if red light is replaced with blue light.

	Q 13. The thermo-emf of a thermocouple is given by the expression, E = a? - ß?2, where '?' is the temperature of the hot 
	         junction. If a = 42µV°C-1, ß = 0.035µV°C-2, calculate the (i) neutral temperature and (ii) temperature of inversion of 
	         the thermocouple, if the cold junction is at 20°C.

	Q 14. Sky waves are not used in transmitting T.V. signals. Why? State two factors by which the range of transmission of 
	         T.V. signals can be increased.

	Q 15. Calculate the current drawn by the primary of a transformer, Which steps down 200 V to 20 V to operate a device of 
	         resistance 20 O. Assume the efficiency of the transformer to be 80%.

	Q 16. Draw a ray diagram showing how the final image of a distant object is formed using an astronomical telescope in the 
	         near point position.

	Q 17. A spherical Gaussian surface encloses a charge of 8.85 * 10-8 C.
	         (i) Calculate the electric flux passing through the surface; 
	         (ii) If the radius of the Gaussian surface is doubled, how would the flux change?

	Q 18. State the condition for diffraction of light to occur. In the diffraction at a single slit experiment, how would the width 
	         and the intensity of central maximum change, if (i) slit width is halved and (ii) visible light of longer wavelength is 
	         used.

	Q 19. A semiconductor has equal electron and hole concentrations of 2 * 108/m3. On doping with a certain impurity, the 
	         hole concentration increases to 4 * 1010/m3.
	         (i) What type of semiconductor is obtained on doping?
	         (ii) Calculate the new electron concentration of semiconductor.
	         (iii) How does the energy gap vary with doping?

	Q 20. Draw the circuit diagram of a common-emitter amplifier, with appropriate biasing. What is the phase difference 
	         between the input and output signals? State two reasons why a common-emitter amplifier is preferred to a common 
	         base amplifier.

	Q 21. A parallel plate capacitor is charged to a potential difference 'V' by a d.c. source. The capacitor is then disconnected 
	         from the source. If the distance between the plates is doubled, state with reason how the following will change:
	         (i) electric field between the plates, (ii) capacitance and (iii) energy stored in the capacitor.

	Q 22. Define 'electrical potential'. Deduce an expression for the electric potential at a point distance 'r' from a point charge 
	         (Q > 0).

	Q 23. Define resistivity and state its S.I. unit. State and explain how the resistivity of a conductor varies with temperature.

	Q 24. The ground state energy of hydrogen atom is -13.6 eV. If an electron makes a transition from an energy level 
	         -0.85 eV to -3.4 eV, calculate the wavelength of the spectral line emitted. To which series of hydrogen spectrum, 
	         does this wavelength belong?

	Q 25. What are coherent sources of light? Deduce an expression for the intensity at any point on the screen in Young's 
	         double slit experiment.

	Q 26. Prove that two parallel conductors of infinite lengths, carrying currents in the same direction attract each other. 
	         Deduce the expression for the force per unit length, experienced by each conductor.

						OR

	         Explain with the help of a labelled diagram the principle, construction and working of a cyclotron.

	Q 27. (a) Define the terms decay constant and half-life of a radioactive sample. Derive the relation connecting the two.
	         (b) How many disintegrations per second will occur in one gram 92U238, if its half-life against alpha decay is 
	             1.42 * 1017s?

	Q 28. Derive an expression for the self-inductance of a long solenoid.
	         An inductor L, a capacitor 20µF, a resistor 1OO are connected in series with an a.c. source of frequency 50 Hz. If 
	         the current is in phase with the voltage, calculate the inductance of the inductor.