 Model Sample Paper - 4 Q.1. What is the work done by the field of a nucleus in a complete circular orbit of the electron? What if the orbit is elliptical? Q.2. Under what circumstances can the terminal potential difference of a battery exceed its e.m.f? Q.3. Why do magnetic lines of force prefer to pass through ferromagnetic materials? Q.4. What feature of electromagnetic waves led Maxwell to postulate that light might be an electromagnetic wave? Q.5. The monochromatic source of light in Young's double slit experiment is replaced by another monochromatic source of shorter wavelength. What will be the effect? Q.6. Calculate the temperature of the star having its maximum emission at 4500A0 You are given that temperature of sun is 6000 K and it has maximum emission at 5000 A0. Q.7. A silver wire is stretched to make it 1% longer. What is the, effect on its (i) resistance (ii) specific resistance? Q.8. Why is the drift velocity of electrons small? Q.9. Explain how you will use a potentiometer to measure the e.m.f. Of a cell? Q.10. What is meant by wave front? Explain three types of wave front? Q.11. Two prisms are made of materials of dispersing power w, and C02- What is the relation between the angles of the prism so that the combination produces deviation without dispersion. Q.12. A biconvex lens is made of glass with m = 1.52. Each surface has a radius of curvature equal to 30 em. An object of height 3-cm is placed 14 em from the lens. Find the focal length of the lens and the position and size of image. Q.13. Explain how will you study the distance and size of the planet? Q.14. A sheet of silver is illuminated by monochromatic ultra violet radiations of wavelength 1810 A0. What is the maximum energy of the emitted electron? Thresholds wavelength of silver is 2640 A0. Q.15. Draw a labelled diagram of a full wave rectifier using p-n junction diodes. Q.16. Derive an expression for torque acting on an electric dipole in a uniform two-dimensional electric field. Q.17. What do you understand by internal resistance and terminal potential difference of cell? On what factors do they depend? Q.18. Why is ammeter connected in series and voltmeter in parallel in the circuit? Q.19. What do you understand by (i) Peltier effect (ii) Thomson's effect? Define Paltier and Thomson's coefficient. Q.20. Distinguish between conductors, insulators and semiconductors on the basis of energy band diagrams. Q.21. Derive an expression for the force between two parallel conductors carrying current in the same direction and hence define one ampere. Q.22. A bar magnet of magnetic moment 1.5 J/T has aligned with the direction of a uniform magnetic field of 0.22-T. (a) What is the amount of work done to turn the magnet so as to align its magnetic moment? (i) normal to the field direction (ii) opposite to the field direction. (b) What is the torque on the magnet in cases (i) and (ii). Q.23. A wheel with 10 metallic spokes each 0.5-m long is rotated with a speed of 120 r.p.m. in a plane normal to earth's magnetic field at the place. If the magnitude of the field is 0.40 gauss, what is the induced e.m.f. between the axle and rim of the wheel? Q.24. In Young's experiment, the width of the fringes obtained with light of wavelength 6000 A0 is 2.0 mm. What, will be the fringe width if the entire apparatus is immersed in a liquid of refracting index 1.33? Q.25. Calculate the frequency of emitted radiations when H atom changes from an energy state n = 2 to n = 1. Q.26. With the help of a circuit diagram explain the use of p-n-p transistor as an amplifier in common emitter configuration. What is the phase relationship between collector and bases voltages? Q.27. Explain, why a convex lens behaves as a converging lens in water (m = 1.33) while it behaves as a diverging lens in carbon-disulphide (m = 1.65)? Q.28. With the help of a labelled diagram, explain the construction and working of a nuclear reactor. Q.29. Explain the principle of a capacitor. Derive an expression for the capacitance of a parallel plate capacitor. or Two extremely small charged copper spheres have their centers separated by a distance of 50 cm in vacuum (a) What is the mutual force of electrostatic repulsion if the change on each is 6.5 x 1 0-7 C.(b) What will be the force of repulsion if (i) charge on each sphere is doubled and their separation is halved? (ii) The two spheres are placed in water? Dielectric constant of water = 80. ? Q. 30. A resistance of 1 0 ohm is joined in series with an inductance of 0 5 henry. What capacitance should be put in series with the combination to obtain maximum current? What will be the potential difference across the resistance, inductance and capacitor? A 200-volt and 50 cycle's a.c. mains are supplying the current.