Sample Paper 01

Sample Paper – 2010Class – XIISubject – PhysicsBased on the new pattern for CBSE board examination 2010Time allowed: 3 hours Maximum Marks : 70General Instructions:All questions are compulsory.Question numbers 1 to 8 are very short answer type questions, carrying one mark each.Question numbers 9 to 18 are short answer type questions, carrying two marks each.Question numbers 19 to 27 are also short answer type questions, carrying three marks each.Question numbers 28 to 30 are long answer type questions, carrying five marks each.Use of calculators is not permitted. However, you may use log tables, if necessary.You may use the following physical constants wherever necessary :c = 3 x 108ms-1h = 6.6 x 10-34Jse = 1.6 x 10-19 Cμo = 4 π x 10−7T m A−1Boltzmann constant k = 1.38 x 1023 JK-1Avogadro’s number NA = 6.023 x 1023/moleMass of neutron mn = 1.6 x 10-27 kgMass of electron me = 9.1 x 10-31 kgAn electron, an alpha particle and a proton have the same kinetic energy. Which one of these particles has the largest d-Broglie wavelength? 1Why should the materials used for making permanent magnets have high coercivity? 1The radioactive isotope decays according to the sequenceD D1 D2 D3If the mass number of atomic number of D3 are 176 and 71 respectively, what is (i) the mass number (ii) atomic number of D ?1What is the modulation of a signal in transmission necessary?1A partially plane polarised beam of light is passed through a polaroid. Show graphically the variation of the transmitted light intensity with angle of rotation of the polaroid. 1How would the angular separation of interference fringes in Young’s double slit experiment change when the distance of separation between the slits and the screen is doubled? 1What do you mean by the impedance of LCR circuit? 1The graph given shows the variation of the total energy (U) stored in a capacitor against the value of the capacitance (C) itself. Which of the two - the charge on the capacitor or the potential used to charge it is kept constant for this graph?1The output of an OR gate is connected to both the inputs of a NAND gate. Draw the logic circuit of this combination of gates and write its truth table. 2Draw a plot of potential energy of a pair of nucleons as a function of their separation. What is the significance of negative potential energy in the graph drawn? 2A convex lens of refractive index 1.5 has a focal length of 18 cm in air. Calculate the change in its focal length when it is immersed in water of refractive index 4/3. 2Distinguish between the terms 'average value' and 'rms value' of an alternating current. The instantaneous current from an a.c. source is 5 sin (314 t) amperes. What are the average and rms values of the current? 2Write the relation for the force F acting on a charge carrier q moving with a velocity v through a magnetic field B in vector notation. Using this relation, deduce the conditions under which this force will be (i) maximum - (ii) minimum. 2A cylindrical metallic wire is stretched to increase its length by 5%. Calculate' the percentage change in its resistance. 2The electric field E due to a point charge at any point near it is defined as E where q0 is the test charge and F is the force acting on it. What is the physical significance of in this expression? Draw the electric field lines of a point charge Q when (i) Q > 0 and (ii) Q < 0. 2Or Define electric flux. Write its SI units. A spherical rubber balloon carries a charge that is uniformly distributed over its surface. As the balloon is blown up and increases in size, how does the total electric flux coming out of the surface change? Give reasons. 2A parallel plate capacitor, each with plate area A and separation d, is charged to a potential difference V. The battery used to charge it is then disconnected. A dielectric slab of thickness d and dielectric constant K is now placed between the plates. What, change, if any, will take place in(i) charge on the plates '(ii) electric field intensity between the plates(iii) capacitance of the capacitor.Justify your answer in each case. 2Given below are two electric circuits A and B. Calculate the power factors of the circuits A and B. 2.A voltage of 30 V is applied across a carbon resistor with first, second and third rings of blue, black and yellow colours respectively. Calculate the value of current through the resistor. 2Deduce an expression for the electric field due to an electric dipole at a point on its axis. Mention one contrasting feature of electric field of a dipole at a point as compared to that due to a single charge. 3State Kirchoff's rules of current distribution in an electrical network. Using these rules determine the value of the current I1 in the electric circuit given below. 3Define the term ‘modulation index’ for an AM wave. What would be the modulation index for an AM wave for which the maximum amplitude is p while the minimum amplitude is q?3Explain with the help of a labelled diagram the underlying principle and working of a step-up transformer. Why cannot such a device be used to step-up d.c. voltage? 3OrDraw a labelled diagram of an a.c. generator. Explain briefly its principle and working. 3A beam of light of wavelength 400 nm is incident normally on a right angled prism as shown. It is observed that the light just grazes along the surface AC after falling on it. Given that the refractive index of the material of the prism varies with the wavelength as per the relation = 1.2 + Calculate the value of b and the refractive index of the prism material for a wavelength = 500 nm. [(Given = Sin-1 (0.625)] 3Define the term resolving power of an astronomical telescope.How does it get affected on:(i) increasing the aperture of the objective lens?(ii) increasing the wavelength of the light used?Justify your answer in each case. 3W'rite any four characteristics of electromagnetic waves. Give two uses each of (i) Radio-waves (ii) Micro waves. 3In a plot of photo-electric current versus anode potential, how(i) the saturation current vary with anode potential for incident radiations of different frequencies but the same intensity ?(ii) the stopping potential vary for incident radiations of different intensities but same frequency?(iii) photoelectric current vary for different intensities but same frequency of incident radiations?Justify your answer in each case. . 3Calculate the amount of energy released during the -decay of + [Given : 1. Atomic mass of = 238.05079 u 2. atomic mass of = 234.04363 u3. atomic mass of = 4.00260 u1u = 931.5 MeV]Is this decay spontaneous? Give reason. 3Draw a labelled diagram of a moving coil galvanometer. State the principle on which it works. Deduce an expression for the torque acting on a rectangular current carrying loop kept in a uniform magnetic field. Write two factors on which the current sensitivity of a moving coil galvanometer depends. 5Or State Biot-Savart law. Use it to derive an expression for the magnetic field at the centre of a circular loop of radius R carrying a steady current I. Sketch the magnetic field lines for such a current carrying loop. 5What are coherent sources? Why are coherent sources required to produce interference of light? Give an example of interference of light in everyday life.In Young's double slit experiment, the two slits are 0.03 cm apart and the screen is placed at a distance of 1.5 m away from the slits. The distance between the central bright fringe and fourth bright fringe is 1 cm. Calculate the wavelength of light used. 5.OrState the condition under which the phenomenon of diffraction of light takes place? Derive an expression for the width of the central maximum due to diffraction of light at a single slit.A slit of width d is illuminated by a monochromatic light of wavelength 700 nm at normal incidence. Calculate the value of 'd' for position of(i) first minimum at an angle of diffraction of 30°. (ii) first maximum at an angle of diffraction of 30°. 5State the principle of working of p-n diode as a rectifier. Explain, with the help of a circuit diagram, the use of p-n diode as a full wave rectifier.Draw sketch of the input and output waveforms. 5OrDraw the symbolic representation of a (i) p-n-p, (ii) n-p-n transistor. Why is the base region of transistor thin and lightly doped? With proper circuit diagram, show the biasing of a p-n-p transistor in common base configuration.Explain the movement of charge carriers through different parts of the transistor in such a configuration and show that IE =Ic+ lB, 5