ISC Physics Class 12 Past Paper PDF

PHYSICS (861) CLASS XII There will be two papers in the subject: Paper II: Practical - 3 hours... 15 marks Paper I: Theory -...

PHYSICS (861) CLASS XII There will be two papers in the subject: Paper II: Practical - 3 hours... 15 marks Paper I: Theory - 3 hours...70 marks Project Work... 10 marks Practical File... 5 marks PAPER I- THEORY: 70 Marks S. NO. UNIT TOTAL WEIGHTAGE 1. Electrostatics 14 Marks 2. Current Electricity 3. Magnetic Effects of Current and Magnetism 16 Marks 4. Electromagnetic Induction and Alternating Currents 5. Electromagnetic Waves 6. Optics 20 Marks 7. Dual Nature of Radiation and Matter 13 Marks 8. Atoms and Nuclei 9. Electronic Devices 7 Marks TOTAL 70 Marks 1   PAPER I -THEORY- 70 Marks field E experiences an electric   Note: (i) Unless otherwise specified, only S. I. Units force FE = qE. Intensity due to a are to be used while teaching and learning, as well as continuous distribution of charge i.e. for answering questions. linear, surface and volume. (ii) All physical quantities to be defined as and when (c) Electric lines of force: A convenient way they are introduced along with their units and to visualize the electric field; properties dimensions. of lines of force; examples of the lines of (iii) Numerical problems are included from all topics force due to (i) an isolated point charge except where they are specifically excluded or where (+ve and - ve); (ii) dipole, (iii) two only qualitative treatment is required. similar charges at a small distance;(iv) uniform field between two oppositely 1. Electrostatics charged parallel plates. (i) Electric Charges and Fields (d) Electric dipole and dipole moment;  Electric charges; conservation and derivation of the E at a point, (1) on the quantisation of charge, Coulomb's law; axis (end on position) (2) on the superposition principle and continuous perpendicular bisector (equatorial i.e. charge distribution. broad side on position) of a dipole, also Electric field, electric field due to a point for r>> 2l (short dipole); dipole in a charge, electric field lines, electric dipole, uniform electric field; net force zero, electric field due to a dipole, torque on a torque on an electric dipole: dipole in uniform electric field.    τ= p × E and its derivation. Electric flux, Gauss’s theorem in (e) Gauss’ theorem: the flux of a vector Electrostatics and its applications to find   field due to infinitely long straight wire, field; Q=vA for velocity vector v A, uniformly charged infinite plane sheet and  A is area vector. Similarly, for electric uniformly charged thin spherical shell.    field E , electric flux φE = EA for E A (a) Coulomb's law, S.I. unit of    charge; permittivity of free space and φE= E ⋅ A for uniform E. For non- and of dielectric medium.   Frictional electricity, electric charges uniform field φE = ∫dφ =∫ E.dA. Special (two types); repulsion and cases for θ = 00, 900 and 1800. Gauss’ attraction; simple atomic structure - theorem, statement: φE =q/∈0 electrons and ions; conductors or φE = where φE is for and insulators; quantization and conservation of electric charge; a closed surface; q is the net charge Coulomb's law in vector form; (position enclosed, ∈o is the permittivity of free coordinates r1, r2 not necessary). space. Essential properties of a Gaussian Comparison with Newton’s law of surface. gravitation; Superposition principle      Applications: Obtain expression for E ( F = 1 ) F 12 + F 13 + F 14 + ⋅⋅⋅. due to 1. an infinite line of charge, 2. a (b) Concept of electric field and its intensity; uniformly charged infinite plane thin examples of different fields; sheet, 3. a thin hollow spherical shell gravitational, electric and magnetic; (inside, on the surface and outside). Electric field due to a point charge Graphical variation of E vs r for a thin    spherical shell. E = F / qo (q0 is a test charge); E for a (ii) Electrostatic Potential, Potential Energy and group of charges (superposition Capacitance principle); a point charge q in an electric 2  Electric potential, potential difference, 1 2 electric potential due to a point charge, a expression for energy stored (U = CV 2 dipole and system of charges; equipotential surfaces, electrical potential energy of a 1 1 Q2 = QV = ) and energy density. system of two point charges and of electric 2 2 C dipole in an electrostatic field. (c) Dielectric constant K = C'/C; this is also Conductors and insulators, free charges and called relative permittivity K = ∈r = ∈/∈o; bound charges inside a conductor. elementary ideas of polarization of matter Dielectrics and electric polarisation, in a uniform electric field qualitative capacitors and capacitance, combination discussion; induced surface charges of capacitors in series and in parallel. weaken the original field; results in Capacitance of a parallel plate capacitor,  reduction in E and hence, in pd, (V); for energy stored in a capacitor. charge remaining the same Q = CV = C' (a) Concept of potential, potential difference V' = K. CV'; V' = V/K; and E ′ = E ; if and potential energy. Equipotential K surface and its properties. Obtain an the Capacitor is kept connected with the expression for electric potential at a source of emf, V is kept constant V = Q/C = point due to a point charge; graphical Q'/C' ; Q'=C'V = K. variation of E and V vs r, VP=W/q0; CV= K. Q increases; For a parallel plate hence VA -VB = WBA/ q0 (taking q0 from B capacitor with a dielectric in between, to A) = (q/4πε0)(1/rA - 1/rB); derive this C' = KC = K.∈o. A/d = ∈r.∈o.A/d. equation; also VA = q/4πε0.1/rA ; for ∈0 A Then C ′ = ; for a capacitor q>0, VA>0 and for qVC dt Substituting pd=current x henry. Expression for coefficient of resistance or reactance, we get mutual inductance of two coaxial Z2=R2+(XL-Xc)2 and solenoids. tanφ = (VL m -VCm)/VRm = (XL-Xc)/R µ0 N1 N 2 A giving I = I m sin (wt-φ) where I m =Vm/Z =M = µ0 n1 N 2 A Induced etc. Special cases for RL and RC circuits. l [May use Kirchoff’s law and obtain the emf opposes changes, back emf is set up, differential equation] Graph of Z vs f and eddy currents. I vs f. Transformer (ideal coupling): principle, (f) Power P associated with LCR circuit = working and uses; step up and step down; efficiency and applications 1 /2VoIo cosφ =VrmsIrms cosφ = Irms2 R; including transmission of power, energy power absorbed and power dissipated; losses and their minimisation. electrical resonance; bandwidth of signals and Q factor (no derivation); (c) Sinusoidal variation of V and I with time, oscillations in an LC circuit (ω0 = for the output from an ac 1/ LC ). Average power consumed generator; time period, frequency and phase changes; obtain mean values of averaged over a full cycle P= current and voltage, obtain relation (1/2) VoIo cosφ, Power factor between RMS value of V and I with peak cosφ = R/Z. Special case for pure R, L values in sinusoidal cases only. and C; choke coil (analytical only), XL controls current but cosφ = 0, hence (d) Variation of voltage and current in a.c. circuits consisting of only a resistor, only P =0, wattless current; LC circuit; at an inductor and only a capacitor (phasor resonance with XL=Xc , Z=Zmin= R, power representation), phase lag and phase delivered to circuit by the source is lead. May apply Kirchhoff’s law and maximum, resonant frequency obtain simple differential equation (SHM 1 f0 =. type), V = Vo sin ωt, solution I = I0 sin 2π LC ωt, I0sin (ωt + π/2) and I0 sin (ωt - π/2) for pure R, C and L circuits respectively. (g) Simple a.c. generators: Principle, Draw phase (or phasor) diagrams description, theory, working and use. showing voltage and current and phase Variation in current and voltage with lag or lead, also showing resistance R, time for a.c. and d.c. Basic differences inductive reactance XL; (XL=ωL) and between a.c. and d.c. capacitive reactance XC, (XC = 1/ωC). 5. Electromagnetic Waves Graph of XL and XC vs f. Basic idea of displacement current. (e) The LCR series circuit: Use phasor Electromagnetic waves, their characteristics, their diagram method to obtain expression for transverse nature (qualitative ideas only). I and V, the pd across R, L and C; and Complete electromagnetic spectrum starting from the net phase lag/lead; use the results of radio waves to gamma rays: elementary facts of 4(e), V lags I by π/2 in a capacitor, V electromagnetic waves and their uses. leads I by π/2 in an inductor, V and I are in phase in a resistor, I is the same in all Concept of displacement current, qualitative three; hence draw phase diagram, descriptions only of electromagnetic spectrum; common features of all regions of 6  electromagnetic spectrum including transverse (d) Refraction at a single spherical surface; nature ( and perpendicular to ); special detailed discussion of one case only - features of the common classification (gamma convex towards rarer medium, for rays, X rays, UV rays, visible light, IR, spherical surface and real image. Derive microwaves, radio and TV waves) in their the relation between n1, n2, u, v and R. production (source), detection and other Refraction through thin lenses: derive properties; uses; approximate range of λ or f or lens maker's formula and lens formula; at least proper order of increasing f or λ. derivation of combined focal length of two thin lenses in contact. Combination 6. Optics of lenses and mirrors (silvering of lens excluded) and magnification for lens, (i) Ray Optics and Optical Instruments derivation for biconvex lens only; extend Ray Optics: Reflection of light by the results to biconcave lens, plano spherical mirrors, mirror formula, convex lens and lens immersed in a refraction of light at plane surfaces, total liquid; power of a lens P=1/f with SI internal reflection and its applications, unit dioptre. For lenses in contact 1/F= optical fibres, refraction at spherical 1/f1+1/f2 and P=P1+P2. Lens formula, surfaces, lenses, thin lens formula, lens formation of image with combination of maker's formula, magnification, power of thin lenses and mirrors. a lens, combination of thin lenses in [Any one sign convention may be used in contact, combination of a lens and a mirror, solving numericals]. refraction and dispersion of light through a (e) Ray diagram and derivation of prism. magnifying power of a simple Optical instruments: Microscopes and microscope with image at D (least astronomical telescopes (reflecting and distance of distinct vision) and infinity; refracting) and their magnifying powers. Ray diagram and derivation of magnifying power of a compound (a) Reflection of light by spherical mirrors. microscope with image at D. Only Mirror formula: its derivation; R=2f for expression for magnifying power of spherical mirrors. Magnification. compound microscope for final image at (b) Refraction of light at a plane interface, infinity. Snell's law; total internal reflection and Ray diagrams of refracting telescope critical angle; total reflecting prisms and with image at infinity as well as at D; optical fibers. Total reflecting prisms: simple explanation; derivation of application to triangular prisms with magnifying power; Ray diagram of angle of the prism 300, 450, 600 and 900 reflecting telescope with image at respectively; ray diagrams for Refraction infinity. Advantages, disadvantages and through a combination of uses. 1 , real depth media, 1 n2 × 2 n3 × 3 n1 = (ii) Wave Optics and apparent depth. Simple applications. Wave front and Huygen's principle. Proof (c) Refraction through a prism, minimum of laws of reflection and refraction using deviation and derivation of Huygen's principle. Interference, Young's relation between n, A and δmin. Include double slit experiment and expression for explanation of i-δ graph, i1 = i2 = i (say) fringe width(β), coherent sources and for δm; from symmetry r1 = r2; refracted sustained interference of light, Fraunhofer ray inside the prism is parallel to the diffraction due to a single slit, width of base of the equilateral prism. Thin prism. central maximum. Dispersion; Angular dispersion; (a) Huygen’s principle: wavefronts - different dispersive power, rainbow - ray diagram types/shapes of wavefronts; proof of laws (no derivation). Simple explanation. 7  of reflection and refraction using explained only assuming quantum (particle) Huygen’s theory. [Refraction through a nature of radiation. Determination of prism and lens on the basis of Huygen’s Planck’s constant (from the graph of theory not required]. stopping potential Vs versus frequency f of (b) Interference of light, interference of the incident light). Momentum of photon monochromatic light by double slit. p=E/c=hν/c=h/λ. Phase of wave motion; superposition of (b) De Broglie hypothesis, phenomenon identical waves at a point, path of electron diffraction (qualitative only). difference and phase difference; coherent Wave nature of radiation is exhibited in and incoherent sources; interference: interference, diffraction and polarisation; constructive and destructive, conditions particle nature is exhibited in photoelectric for sustained interference of light waves effect. Dual nature of matter: particle nature [mathematical deduction of interference common in that it possesses momentum p and from the equations of two progressive kinetic energy KE. The wave nature of waves with a phase difference is not matter was proposed by Louis de Broglie, required]. Young's double slit λ=h/p= h/mv. experiment: set up, diagram, geometrical deduction of path difference ∆x = dsinθ, 8. Atoms and Nuclei between waves from the two slits; using (i) Atoms ∆x=nλ for bright fringe and ∆x= (n+½)λ Alpha-particle scattering experiment; for dark fringe and sin θ = tan θ =yn /D Rutherford's atomic model; Bohr’s atomic as y and θ are small, obtain yn=(D/d)nλ model, energy levels, hydrogen spectrum. and fringe width β=(D/d)λ. Graph of distribution of intensity with angular Rutherford’s nuclear model of atom distance. (mathematical theory of scattering excluded), based on Geiger - Marsden experiment on (c) Single slit Fraunhofer diffraction α-scattering; nuclear radius r in terms of (elementary explanation only). closest approach of α particle to the nucleus, Diffraction at a single slit: experimental setup, diagram, diffraction pattern, obtained by equating ∆K=½ mv2 of the α obtain expression for position of minima, particle to the change in electrostatic a sinθn= nλ, where n = 1,2,3… and potential energy ∆U of the system conditions for secondary maxima, asinθn [ U = 2e × Ze r0∼10-15m = 1 fermi; atomic 4πε 0 r0 =(n+½)λ.; distribution of intensity with structure; only general qualitative ideas, angular distance; angular width of including atomic number Z, Neutron number central bright fringe. N and mass number A. A brief account of 7. Dual Nature of Radiation and Matter historical background leading to Bohr’s Wave particle duality; photoelectric effect, theory of hydrogen spectrum; formulae for Hertz and Lenard's observations; Einstein's wavelength in Lyman, Balmer, Paschen, photoelectric equation - particle nature of light. Brackett and Pfund series. Rydberg constant. Matter waves - wave nature of particles, Bohr’s model of H atom, postulates (Z=1); de-Broglie relation. expressions for orbital velocity, kinetic energy, potential energy, radius of orbit and (a) Photo electric effect, quantization of total energy of electron. Energy level radiation; Einstein's equation diagram, calculation of ∆E, frequency and Emax = hυ - W0; threshold frequency; work wavelength of different lines of emission function; experimental facts of Hertz and spectra; agreement with experimentally Lenard and their conclusions; Einstein used observed values. [Use nm and not Å for unit Planck’s ideas and extended it to apply for ofλ]. radiation (light); photoelectric effect can be 8 (ii) Nuclei production in the sun and stars. [Details of chain reaction not required]. Composition and size of nucleus. Mass- energy relation, mass defect; binding 9. Electronic Devices energy per nucleon and its variation with (i) Semiconductor Electronics: Materials, mass number; Nuclear reactions, nuclear Devices and Simple Circuits. Energy bands in fission and nuclear fusion. conductors, semiconductors and insulators (a) Atomic masses and nuclear density; (qualitative ideas only). Intrinsic and Isotopes, Isobars and Isotones – extrinsic semiconductors. definitions with examples of each. (ii) Semiconductor diode: I-V characteristics in Unified atomic mass unit, symbol u, forward and reverse bias, diode as a rectifier; 1u=1/12 of the mass of 12C atom = Special types of junction diodes: LED, 1.66x10-27kg). Composition of nucleus; photodiode and solar cell. mass defect and binding energy, BE= (a) Energy bands in solids; energy band (∆m) c2. Graph of BE/nucleon versus diagrams for distinction between mass number A, special features - less conductors, insulators and semi- BE/nucleon for light as well as heavy conductors - intrinsic and extrinsic; elements. Middle order more stable [see electrons and holes in semiconductors. fission and fusion] Einstein’s equation E=mc2. Calculations related to this Elementary ideas about electrical equation; mass defect/binding energy, conduction in metals [crystal structure mutual annihilation and pair production not included]. Energy levels (as for as examples. hydrogen atom), 1s, 2s, 2p, 3s, etc. of an isolated atom such as that of copper; (b) Nuclear Energy these split, eventually forming ‘bands’ of Theoretical (qualitative) prediction of energy levels, as we consider solid exothermic (with release of energy) copper made up of a large number of nuclear reaction, in fusing together two isolated atoms, brought together to form light nuclei to form a heavier nucleus a lattice; definition of energy bands - and in splitting heavy nucleus to form groups of closely spaced energy levels middle order (lower mass number) separated by band gaps called forbidden nuclei, is evident from the shape of BE bands. An idealized representation of the per nucleon versus mass number graph. energy bands for a conductor, Also calculate the disintegration energy insulator and semiconductor; Q for a heavy nucleus (A=240) with characteristics, differences; distinction BE/A ∼ 7.6 MeV per nucleon split into between conductors, insulators and two equal halves with A=120 each and semiconductors on the basis of energy BE/A ∼ 8.5 MeV/nucleon; Q ∼ 200 MeV. bands, with examples; qualitative Nuclear fission: Any one equation of discussion only; energy gaps (eV) in fission reaction. Chain reaction- typical substances (carbon, Ge, Si); some controlled and uncontrolled; nuclear electrical properties of semiconductors. reactor and nuclear bomb. Main parts of Majority and minority charge carriers - a nuclear reactor including their electrons and holes; intrinsic and functions - fuel elements, moderator, extrinsic, doping, p-type, n-type; donor control rods, coolant, casing; criticality; and acceptor impurities. utilization of energy output - all (b) Junction diode and its symbol; depletion qualitative only. Fusion, simple example region and potential barrier; forward of 4 1H→4He and its nuclear reaction and reverse biasing, V-I characteristics equation; requires very high temperature and numericals; half wave and a full ∼ 106 degrees; difficult to achieve; wave rectifier. Simple circuit diagrams hydrogen bomb; thermonuclear energy and graphs, function of each component 9  in the electric circuits, qualitative only. (ii) Selection of origin (should be marked by two [Bridge rectifier of 4 diodes not coordinates, example 0,0 or 5,0, or 0,10 or 30,5; included]; elementary ideas on solar Kink is not accepted). cell, photodiode and light emitting diode (i) The axes should be labelled according to the (LED) as semi conducting diodes. question Importance of LED’s as they save energy without causing atmospheric pollution (ii) Uniform and convenient scale should be taken and global warming. and the units given along each axis (one small division = 0.33, 0.67, 0.66, etc. should not to be PAPER II taken) PRACTICAL WORK- 15 Marks (iii) Maximum area of graph paper (at least 60% of The experiments for laboratory work and practical the graph paper along both the axes) should examinations are mostly from two groups: be used. (i) experiments based on ray optics and (iv) Points should be plotted with great care, (ii) experiments based on current electricity. marking the points plotted with (should be a The main skill required in group (i) is to remove circle with a dot)  or ⊗. A blob ( ) is a parallax between a needle and the real image of misplot. another needle. (v) The best fit straight line should be drawn. The In group (ii), understanding circuit diagram and making connections strictly following the given best fit line does not necessarily have to pass diagram is very important. Polarity of cells and through all the plotted points and the origin. meters, their range, zero error, least count, etc. should While drawing the best fit line, all be taken care of. experimental points must be kept on the line or symmetrically placed on the left and right A graph is a convenient and effective way of side of the line. The line should be continuous, representing results of measurement. It is an important part of the experiment. thin, uniform and extended beyond the extreme plots. There will be one graph in the Practical question paper. (vi) The intercepts must be read carefully. Y intercept i.e. y0 is that value of y when x = 0. Candidates are advised to read the question paper Similarly, X intercept i.e. x0 is that value of x carefully and do the work according to the when y=0. When x0 and y0 are to be read, instructions given in the question paper. Generally they are not expected to write the procedure of the origin should be at (0, 0). experiment, formulae, precautions, or draw the Deductions figures, circuit diagrams, etc. (i) The slope ‘S’ of the best fit line must be found Observations should be recorded in a tabular form. taking two distant points (using more than 50% Record of observations of the line drawn), which are not the plotted y − y1 ∆y All observations recorded should be consistent points, using S = 2 =. Slope S must with the least count of the instrument used (e.g. x2 − x1 ∆x focal length of the lens is 10.0 cm or 15.1cm but be calculated upto proper decimal place or 10 cm is a wrong record.) significant figures as specified in the question paper. All observations should be recorded with correct units. (ii) All calculations should be rounded off upto proper decimal place or significant figures, as Graph work specified in the question papers. Students should learn to draw graphs correctly noting NOTE: all important steps such as: (i) Title Short answer type questions may be set from each experiment to test understanding of theory and logic of steps involved. 10 Given below is a list of required experiments. 9. Verify Ohm’s law for the given unknown Teachers may add to this list, keeping in mind the resistance (a 60 cm constantan wire), plotting a general pattern of questions asked in the annual graph of potential difference versus current. Also examinations. calculate the resistance per cm of the wire from the slope of the graph and the length of the wire. Students are required to have completed all experiments from the given list (excluding 10. To determine the internal resistance of a cell by a demonstration experiments): potentiometer. 1. To find focal length of a convex lens by using u- 11. From a potentiometer set up, measure the fall in v method (no parallax method) potential (i.e. pd) for increasing lengths of a constantan wire, through which a steady current Using a convex lens, optical bench/metre scales is flowing; plot a graph of pd (V) versus length and two pins, obtain the positions of the images (l). Calculate the potential gradient of the wire for various positions of the object; f