Roll No. Please check that this question paper contains 7 printed pages Please check that this question paper contains 26 questions. Please write down the Serial Number of the question before attempting it. PHYSICS Time allowed : 3 Hours] [Maximum Marks : 70 General Instructions : (a) All questions are compulsory. There are 26 questions in total. (b) This question paper has five sections. (c) Section A contains five question of one marks each. Section contains five question of two marks each, Section C contains twelve question of three marks each Section D contains one value based question of four marks each Section E contains three question of five each. (d) There is no overall choice. Internal choices are provided in one question of three marks and all three questions of five marks each. (e) Following physical constants may be used wherever necessary : c = 3 x 10 8 m/s h = 6.626 x 10-34 Js e = 1.602 x 10-19 C μ 0 = 4π x 10-7 TmA -1 1/4πε 0... = 9 x 109 Nm 2 C -2 Mass of neutron = 1.675 x 10-27 kg
Section A 1. Write the frequency range for each of the following : (a) Standard AM broadcast (b) Satellite Communication 2. Sketch the graph showing the variation of resistivity of silicon with temperature 3. Why is diamagnetic independent of temperature? 4. Name the physical quantity whose S.I. units is web m 5. How does the power of a convex lens vary if the incident red light is replaced by violet light? Section 6. (i) How does the stopping potential applied to a photocell change, if the distance between the light source and cathode of the cell is doubled? (ii) A difference of 2.3ev separates two energy levels in an atom. What is the frequency of radiation emitted when the atom make a transition from the upper level to the lower level? 7. Sketch the output Y from a NAND gate having inputs A and given. A 1 0 1 0 8. A uniform magnetic field of 0.3T is acting as shown in the figure. A rectangular loop of 2 10 5cm carries a current of 12A, what is torque on each loop? y y x z x z
9. y what percentage will the transmission range of a TV tower be affected when the height of the tower is increased by 21%. An average induced e.m.f. of 0.4V appears in a coil when the current in it is changed from 10A in the direction 20A in the opposite direction in 0.40 seconds. Find the coefficient of self induction. 10. Explain the inding Energy Curve. Section C 11. A metallic rod of 1m length is rotated with a frequency of 50 rev/sec with one end hinged at centre and the tower end at the circumference of a circular metallic ring of radius 1m, about an axis passing through the centre and perpendicular to the plane of ring. A constant and uniform magnetic field of 1T parallel to the axis is present everywhere. What is the e.m.f. between centre and metallic ring? 12. What is meant by term modulation? Draw a block diagram of a simple modulator for obtaining an AM signal. 13. Derive the Snell s law by using Hugen s Principle. How the angular separation and visibility of fringes in Young will s double slit experiment. Change when (i) Screen in moved away from the plane of slits, (ii) Width of the source slit is increased. 14. The figure shoes V-I characteristic of a semi-conductor diode: (i) (ii) Identity the semiconductor diode used. Draw the circuit diagram to obtain the given characteristics of this device. ma I 6 5 4 3 2 1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 V(Volts)
15. A transistor has a current amplification factor (current gain) of 50. In C-E configuration circuit the collector resistance is chosen as 50K and the input resistance is 1K. Calculate the output voltage if input voltage is 0.01 V. 16. (a) Determine the electrostatic potential energy of a system consisting two charges 7 c and 2 c (and with no external field) placed at (-9cm, 0,0) and (9cm,0,0) respectively. (b) Suppose that same system of changes is now placed in an external electric field 1 E A r 2, 5 2 A 9 10 c/ m what would the electrostatic energy of the configuration be? 17. A network of resistors is connected to a 16V battery with internal resistance of 1, as shown in fig. (a) Compute the equivalent resistance of the network. (b) Obtain the current in each resistor. (c) Obtain the voltage drops VA, V C and V CD 4 1 12 4 16V 1 6 A resistance of R draws current from a potentiometer. The potentiometer has total resistance. A voltage V is supplied to the potentiometer. Derive an expression for the voltage across R when the sliding contact is in the middle of the potentiometer. A V C R 18. Fig shows a long straight wire of a circular cross-section (radius a) carrying steady current i. The current is uniformly distributed across section. Calculate the magnetic field in the region r < a and r > a. Also plot the variation of with r. I O a
Two thing long parallel wires separated by distance d are carrying a current each. find the magnitude of force per unit length exerted by one wire on other. A m Sin 2 19. Prove the prism formula : A Sin 2 20. In a plane electromagnetic wave the electric field oscillates sinsuoidally with a frequency of 10 2 10 Hz and amplitude 48 V / m (a) What is the wavelength of e.m. wave? (b) Calculate the amplitude of oscillating magnetic field? (c) Calculate the average energy density of the electromagnetic equation. 21. Explain the term stopping potential and frequency in photoelectric emission. Draw graph showing the variation of stopping potential with frequency of the incident light in relation to the photoelectric effect. Deduce the expression for slope of the graph using Einstein Photoelectric equation. 22. Define term half-life period and decay constant of a radioactive substance. Write their S.I. unit Establish relation between two. With the help of a labelled circuit diagram of a npn transistor in CE configuration, explain the input and output characteristics. Section D 23. Kajol s grandfather was reading an article in a newspaper. He read that after so many years of atomic bombing in Hiroshima and Nagasaki, Japan National Census indicated.that children born even now are genetically deformed. Her grandfather was not able to understand the reason behind it. He asked his grand daughter Kajol, who was a science student of Class XII. Kajol sat with her grandfather and showed him pictures from some books and explained the harmful effect of radiations. (a) What are the value displayed by Kajol? (b) Name the nuclear reactions that occur in an atomic bomb (c) Name the working principle of a nuclear reaction.
Section E 24. (a) Derive the expression for the energy density for a parallel plate capacitor. (b) A capacitor is changed with a battery and then its plate separation is increased without disconnecting the battery what will be the change in a. Charged stored in capacitor b. Energy stored in capacitor c. Potential difference across the plates of the capacitor (a) State the Gauss s theorem in electrostatics. (b) y X z 10 Electric field in the above figure is directed along +x direction and given by E 5Ax 2 where E is in N/C and x in metre. A and are constant with dimensions. Taking A10 N / C m and 5 N / C Calculate (i) (ii) The electric flux through cube Net charge enclosed within the cube. 25. (a) In a series LCR a.c. circuit, is the applied instantaneous voltage is equal to the algebraic sum of instantaneous voltage across the series element of the circuit? Is the same true for r.m.s voltage (b) Prove that in a series LCR circuit, the power dissipated depends not only on the voltage and current but also on the cosine of the phase angle between these two (a) State Faraday s law of electromagnetic induction. (b) Figure shows a rectangular conductor PQRS in which the conductor PQ is free to move in uniform magnetic field perpendicular to the plane of paper. The field extend from x 0 to x b and in zero for x b. Assume that only in the arm PQ possesses resistance R when the arm PQ is pulled outward from x 0to x 2b and is the moved
backward to x 0 with constant speed v. Obtain the expression for the flux and induced e.m.f. Sketch the variation of these quantities with distance 0 x b. 26. (a)draw a labelled ray diagram of an astronomical telescope used in normal adjustment position. Write the expression for its magnifying power. (b) Find the position of the image formed by the lens combination given in the figure. f1 10cm f2 10cm f3 30cm 30cm 5cm 10cm (a) Show by a diagram the image formation of a point object by a thin double convex lens 1 1 1 having radii of curvature R 1 and R 2. Hence derive the formula 1, f R1 R2 where f is the focal length and is the refractive index of material of the lens. (b) Draw a labelled ray diagram showing the image formation by a compound microscope in normal adjustment position Write the expression for the magnifying power.