Sample paper 2 kho tài liệu bách khoa

Sample Question Paper – II Time : Hours Maximum Marks :70 General Instructions (i) (ii) All questions are compulsory There is no overall choice However, an internal choice has been provided in one question of two marks, one question of three marks and one question of five marks You have to attempt only one of the choices in such questions (iii) Question number to are very short answer questions, carrying mark each (iv) Question number to 12 are short answer questions, carrying marks each (v) Question number 13 to 24 are also short answer questions, carrying marks each (vi) Question number 25 to 27 are long answer questions, carrying marks each (vii) Use of calculators is NOT permitted However, you may use Log Tables, if necessary (viii) You may use the following physical constants wherever necessary: c = × 108 ms–1 h = 6.6 × 10–34 Js e = 1.6 × 1019 C à0 = ì 10–7 T mA–1 Write the SI unit of (i) potential gradient (ii) electric dipole moment Name any two types of button cells State the main function of a modem A thin prism of refracting angle 2° deviates an incident ray through an angle of 1° Find the value of refractive index of the material of the prism S Chand & Company Limited A radioactive nucleus decays by emiting a β-particle How will the proton-neutron ratio of the daughter nucleus change as compared to the parent nucleus? Name one ohmic material and one non-ohmic device Draw V-I graph for each Define angle of dip at a place How does its value change as one goes from magnetic pole to the magnetic equator? In the given circuit diagram, calculate the value of R using Kirchhoff’s laws 2A E 10V 2.5 R 1A Two identical bar magnets P and Q are placed in two identical uniform magnetic fields as shown in the figure Justify that both the magnets are in equilibrium Which one of these is in stable equilibrium? Give reasons for your answer P N Q S S N S Chand & Company Limited 10 The truth table of a logic gate is given below INPUTS OUTPUT A B Y 0 1 1 1 Name the gate and draw its logic symbol 11 A student is asked to calculate the ratio of electric flux through the surfaces of spheres S1 and S2 with charges placed inside, as shown in the figure He gets the answer as : Check the correctness of the answer by actually calculating the electric flux ratio through the two surfaces and state whether his answer is correct or incorrect S1 +1 mC 5cm S2 3mC 10cm 12 In a part of the circuit shown in the figure, the rate of heat dissipation in 4Ω resistor is 100 J/s Calculate the heat dissipated in the 3Ω resistor in 10 seconds S Chand & Company Limited R1 R2 R3 OR A copper voltameter and a bulb of rating 100W-220V are connected in series across a DC supply If 0.198g of copper is deposited on the electrode in 40 minutes, calculate the potential difference across the bulb assuming that its resistance is approximately constant E.C.E of copper = 0.00033 g/C 13 Name the constituent radiation of electromagnetic spectrum which (i) is similar to the radiations emitted during decay of radioactive nuclei (ii) has its wavelength range between 390 nm and 770 nm (iii)is used in satellite communication (iv) is absorbed from sunlight by the ozone layer (v) is used for studying crystal structures (vi) produces intense heating effect 14 Define the terms ‘solar constant’ and ‘solar luminosity’ Write the relation between the two 15 What the acronyms LASER and LED stand for? Name the factor which determines (i) frequency (ii) intensity of light emitted by LED State the basic difference between the light emitted by LASER and LED S Chand & Company Limited 16 17 18 19 20 21 22 22 A proton and an alpha particle enter at right angles in to a uniform magnetic field of intensity B Calculate the ratio of the radii of their paths, when they enter the field with the (i) same momentum, (ii) same kinetic energy Write two differences between interference and diffraction Two plane monochromatic waves propagating in the same direction with amplitudes A and 2A and differing in phase by π/3 superpose Calculate the amplitude of the resultant wave A ray of light goes from medium to medium Velocity of light in the two media are c1 and c2 respectively For an angle of incidence θ in medium 1, the corresponding angle of refraction in medium is θ/2 (i) Which of the two media is optically denser and why? (ii) Establish the relationship between θ, c1 and c2 Calculate the de Broglie wavelength associated with an electron of energy 200 eV What will be the change in this wavelength if the accelerating protential is increased to four times its earlier value? Prove mathematically that the fraction N/N0, of a radioactive element left over after a time t equals 1/x where x = 2t/T and T denotes half life period of the radioactive element Mention any two special characteristics of light sources used in optical communication Explain the meaning of the terms (i) sensitivity (ii) responsivity of the detector used in an optical communication system Name two such optical detectors Two metallic wires of the same material and same length but different cross sectional areas are joined together (i) in series (ii) in parallel, to source of emf In which of the two wires will the drift velocity of electron be more in each of the two cases and why? OR Six equal resistors, each of value R, are joined together as shown in the given figure Calculate the equivalent resistance across AB S Chand & Company Limited R A R C R D R E R B R F If a supply of emf E is connected across AB, compute the currents through the arms DF and that through the battery 23 A rectangular coil P is moved from a point A to another point B with uniform velocity v through a region of a uniform magnetic field acting normally inwards as shown in the figure Show graphically (i) the variation of magnetic flux associated with the coil with time (ii) variation of induced emf across points X and Y of the coil with time A X P B v X X X X X X X X X Y Explain the nature of variation in magnetic flux as represented by the graph in first case S Chand & Company Limited 24 Two convex lenses A and B of an astronomical telescope having focal lengths cm and 20 cm respectively, are arranged as shown in the figure A B 15cm (i) Which one of the two lenses you will select to use as the objective lens and why? (ii) What should be the change in the distance between the lenses to have the telescope in its normal adjustment position? (iii)Calculate the magnifying power of the telescope in the normal adjustment position 25 Explain the formation of the depletion layer and the barrier potential in a p-n junction diode Also explain with the help of a circuit diagram, its use as a full wave rectifier Draw the input and the corresponding output voltage time waveforms 26 Two circular metal plates, each of radius 10 cm, are kept parallel to each other at a distance of mm What kind of capacitor they make? Mention one application of this capacitor If the radius of each of the plates is increased by a factor of √2 and their distance of separation decreased to half of its initial value, calculate the ratio of the capacitance in the two cases Suggest any one possible method by which the capacitance in the second case be increased by n times S Chand & Company Limited 27 Distinguish between the terms resistance and impedance of an a.c circuit A capacitor C and a resistor R are connected in series in an a.c circuit Deduce, by drawing phasor diagram, a mathematical expression for the impedance of this circuit How will this impedance be affected when the frequency of the applied signal is decreased and why? 2+2+1=5 OR An inductor L, a capacitor C and a resistor R are connected in series in an a.c circuit Deduce, with the help of suitable phasor diagrams, a mathematical expression for impedance of this circuit What is meant by resonance of this circuit? Prove that this circuit exhibits resonance at a frequency give by 3+1+1 2π × LC ANSWERS (i) Volt/m or N/C (ii) Coulomb metre ½+½ Any two of the following: ½+½ Mercury cell, Lithium cell, Silver oxide cell, Alkaline cell Statement of function of a modem: modulation demodulation modem converts digital to analog signals (modulation) and vice-versa (demodulation) µ = 1.5 There will be increase in the proton-neutron ratio S Chand & Company Limited Metallic conducting wire/resistance wire ½ I V p-n junction/copper voltameter or any other I ½ I V V Angle of dip at a place is the angle that earth’s magnetic field makes with the horizontal at that place As we move from magnetic pole to the magnetic equator the angle of dip decrease from 90° to 0° S Chand & Company Limited A 2A 10V D E 2.5 2A B x 1A 1A C x = + = 3A (junction rule) ½ from loop ADCBA –2.5 × – × R + 10 = ½ –5 + 10 – R = R = 5/3 Ω In both the magnets net force = net torque = hence equilibrium Magnet Q is stable because its PE is minimum OR ½+½ If the magnet P is disturbed, a torque acts on it that tries to align it in opposite direction, whereas for magnet Q the torque brings it back to the same alignment S Chand & Company Limited 10 NAND gate A Y B 11 Flux through S1 φ1 = = q1 + q2 ε0 ½ × 10 −16 8.85 × 10 −12 = 4.52 × 105 (N/C) m2 ½ Flux through S2 φ2 = 4.52 × 105 (N/C) m2 ½ Flux is same through both the surfaces and his answer is incorrect ½ 12 I1 R1 R2 R3 I2 6I1 = 3I2 ⇒ I2 = 2I1 S Chand & Company Limited ½ I22 = 4I12 Rate of heat dissipated in R1 = R1 I21 = 4I12 = 100 (given) I12 = 25 A2 ½ Rate of heat dissipation in R3 = R3 I2 = 4I12 ×3 = × 25 × J/s = 300 J/s ½ In 10 second, heat dissipated in R3 = 300 × 10 = 3000 J ½ OR m = ItZ 0.198 = I × 40 × 60 × 0.00033 I = 1/4 A ½ Resistance of the bulb R = P.D across the bulb V P 220 × 220 = 100 = 484 Ω ½ = IR × 484 = 121 V = S Chand & Company Limited ½ 13 (i) γ-rays (ii) Visible light (iii) Microwaves (iv) Ultraviolet (v) X-rays (vi) Infrared rays 14 (ẵ ì = 3) Solar constant (S) is defined as the amount of radiant energy received per second by a unit area of a perfectly black body surface held at right angle to the direction of sun rays at the mean distance of the earth from the sun Solar luminosity (Ls) is defined as amount of total energy emitted per second by the sun in all directions Ls = 4πr2S where r is the mean distance of the earth from the sun 15 LASER — Light Amplification by Stimulated Emission of Radiation ½ LED ½ (i) — Light Emitting Diode Frequency of light emitted by LED depends on gap in energy band of PN junction ½ (ii) Intensity of light emitted by LED is determined by its forward current at PN junction ½ 16 LASER: Light emitted is coherent and monochromatic ½ LED: Light emitted is noncoherent ½ R = mv/Bq ½ (i) For same momentum S Chand & Company Limited R = p/Bq ½ Rα / Rp = qp / qα = ½ ½ (ii) For same K.E R= RP = Rα 2mk Bq mP qα mα qP ½ = 1:1 Any two differences = 17 AR = = 18 ½+½ A12 + A22 + A1 A2 cos φ A2 + (2 A) + A × 2A cos π = 7A Medium is optically denser ẵ sin i à= sin r S Chand & Company Limited = sinθ θ = cos θ sin µ = c1 / c2 ½ ∴ c1 / c2 = cos θ/2 OR 19 θ = cos (c1/2c2) –1 E = 200 eV = 200 × 1.6 × 10–19 J = = ẵ h 2mE 6.6 ì 1034 × 9.1 × 10 −31 × 3.2 × 10 −17 m = 0.8646 Å Wave length would become ½ of its initial value 20 –λt N = N0 e ⇒ N0 / N = e λt ½ N  Log e   = λ t  N  ½ Loge T ½ λ= N Log e   N  t   =  T  Log e    S Chand & Company Limited ½ t    = Log e 2 T  = Logex 21 ½ N0 =x N N = N0 x Characteristics (any two) (i) ½ Size of the source should be small (ii) Light source should produce monochromatic light (iii) Should be capable to rapid switching Sensitivity: It is the measure of the ability of a detector and determines how weak a signal can be detected Responsivity: The ability of the optical detector to respond quickly to the changing light pulses that are rapidly switching ON and OFF Name of optical detectors (any two) Silicon photo-diodes, Avlanche Photo Diodes (APD), photo-transistors, photo-resistors 22 I = neAvd ½ (i) In series, I is constant ½ 1 vd ∝    A ½ S Chand & Company Limited ∴ thinner wire will have greater vd (ii) In parallel, V is same R I1 A = I A2 I∝ From above R =ρ l A ½ I1 A1  vd  A1 =  = I A2  vd  A2 ∴ vd1 = vd2 i.e same drift velocity for both wires ½ OR 22 D R R R R R R E R R R R A R F B A S Chand & Company Limited B Total resistance R′ = I I I I = + + R′ R 2R 2R R Current through battery = 2E R Current through DF = 23 Explanation variation of magnetic flux with time, magnetic flux is proportional to the area of coil associated with flux Area of the coil in the field increases linearly with time Then remains constant when the coil is completely in the magnetic field After this flux decreases linearly with time and goes to zero till it comes out of the magnetic field 1½ 24 (i) Objective lens – B because it has larger focal length and larger aperture (ii) The distance between the lenses has to the increased by 10 cm (iii) m = =4 fo fe ½ ½ S Chand & Company Limited ½ 25 Explanation of depletion layer Explanation of barrier potential Circuit diagram of full wave rectifier 1½ Description of how it is used as full wave rectifier V t t 26 (i) Parallel plate capacitor Applications:- (a) to store electrostatic energy (b) it can be used in an oscillatory circuit, when combined with an inductor ½ (ii) C1 = ε0 A1 d1 = ε0 πr d ( ) ε0 π r ε A C2 = = d d2 2 S Chand & Company Limited ½ = 4ε πr d ½ C1 = C2 (iii) (a) By introducing a dielectric having a dielectric constant n, between the plates (b) By decreasing the distance between the plates by a factor of n (c) By increasing the area of plates n times (any one) (d) By increasing the area of plates between plates by a factor 27 n times and simultaneously decreaing the distance n Distinction between resistance and impedance Circuit diagram for series CR circuit Phasor diagram for series CR circuit Derivation of mathematical expression ½ Z = R2 + 1 ω2 C Z increases because of an increase in the impedance of the capacitor ωC OR Circuit diagram for series LCR circuit ½ Phasor diagram for series LCR circuit ½ S Chand & Company Limited Derivation of mathematical expression 1/ 2     Z =  R +  ωL −   ωC     The current in the circuit rises to a maximum value due to its impedance attaining its minimum value Proof of formula for resonant frequency S Chand & Company Limited ... q2 ẵ ì 10 16 8.85 ì 10 12 = 4. 52 ì 105 (N/C) m2 ẵ Flux through S2 = 4. 52 ì 105 (N/C) m2 ẵ Flux is same through both the surfaces and his answer is incorrect ½ 12 I1 R1 R2 R3 I2 6I1 = 3I2 ⇒ I2... 3I2 ⇒ I2 = 2I1 S Chand & Company Limited ½ I 22 = 4I 12 Rate of heat dissipated in R1 = R1 I21 = 4I 12 = 100 (given) I 12 = 25 A2 ½ Rate of heat dissipation in R3 = R3 I2 = 4I 12 ×3 = ì 25 ì J/s =... Limited = sinθ θ = cos θ sin = c1 / c2 ẵ c1 / c2 = cos θ /2 OR 19 θ = cos (c1/2c2) –1 E = 20 0 eV = 20 0 × 1.6 × 10–19 J λ= = ½ h 2mE 6.6 × 1034 × 9.1 × 10 −31 × 3 .2 × 10 −17 m = 0.8646 Å Wave length