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CBSE XII Pre Boards II 2014 : PHYSICS with Answers (KV Chennai)

9 pages, 44 questions, 4 questions with responses, 4 total responses,

Kendriya Vidyalaya KV IIT Chennai
Kendriya Vidyalaya (KV), IIT Chennai

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KENDRIYA VIDYALAYA SANGATHAN, CHENNAI REGION Class-XII Common Pre-Board Examination-2013 - 14 Physics(Theory)-Marking Scheme 1. T = 24000 years = t = 72000 years = ( )3 = or 12.5% 2. Unit: Am2 Direction: from S-pole to N-pole 3. 2 : 1 4. No, since there is no change in magnetic flux due to steady current 5. (a) equal (b) nx > nr 6. focal length increases, power will decreases 7. A b r, b> r 8. No 1m 1/2 1m 1m + 1m 1m 1/2 9. Depletion region decreases when it is forward biased m Depletion region increases when it is reverse biased m Depletion region decreases with increase in concentration 1m 10.(i) length of antenna required is so large, practically impossible to set up. (ii)Energy radiated from the antenna in audio frequency range is nearly zero (iii) Audio signals from different stations gets inseparably mixed up. (any two) 2m = 22/220 = 0.1A 11.Is = 1m EpIp = EsIs Ip = 0.01A 1m 12. a.Due to a.c source in loop of coil P magnetic flux changes with time. Due to the mutual induction ,induced emf is produced in the coil Q. The bulb lights. 1m b. Decrease in mutual induction and hence a decrease in induced emf in the coil Q. Bulb B gets dimmer. 1m 13. Bqv = r1 = r2 = 1m -2= = =2 1m 14. a. Paramagnetic materials have small positive susceptibility ( ) Ferromagnetic materials have large positive susceptibility Material A is paramagnetic and B is Ferromagnetic. b. Intensity of magnetization of B is very large. Hence large susceptibility 1m 15. a) E0 = cB0 = 120 N/c X 8 rad/s = 1.05 rad/m ( each.) 16. E = = 4.5 eV The photon of energy 4.5 eV will be emitted for corresponding to the transition B 1m 1m 17. i)If the radius of the Gaussian surface were doubled, the electric flux will remain same. The same charge is enclosed in the two cases. 1m ii) the charge is negative. iii) q = 0 -8.854 X 10-9C 18. For correct principle 1m 1m 1m For circuit diagram 1m For explanation and formula 1m 19. A metal has positive temperature coefficient of resistance A semiconductor has negative temperature coefficient of resistance 1m On cooling resistance of Cu increases and for semiconductor decreases 1m The conductivity of Cu decreases and for semiconductor increases OR 1m -3R= 1m R1 = R2 = 1m = 1m 20. Biot-Savert law expression For proper diagram and explanation For correct Expression 1m 1m 1m 21. any one difference 1m for correct phasor diagram 1m For correct derivation and expression 1m 22. For diagram & explanation For I v For correct derivation 1m 1m 1m 23. For correct definition + For correct graph 1m Slope = 1m 24. For correct definition 1m For correct graph 1m For salient features 1m 25. For correct definition of modulation 1/2m Definition of amplitude modulation 1m Waveform diagram 1m Definition of modulation index 1/2m -426. i B problem of reading the book. P 1m (ii) As the person wants to read at 25 cm, so if u = -25 cm then its image should by spectacle lens at v = -50 cm, so that the defective eye may focus it on retina.1m = + = + = F = +50 cm (convex lens) = 0.5 m Power of the lens = =2D 1m (iii) Compassion for others, caring nature. 1m 27. a) i) Derivation of electric potential at any point 2m ii) Derivation of electric potential along axial line 1m b) i) q1 is positive m q2 is negative ii) Slope of the graph = m . As the magnitude of the slope of line due to charge q2 is greater and hence q2 is greater. 1m OR i) C= ii) W Then C = The capacitance will be more in case of metallic slab. 28. For correct ray diagram For working and derivation For reason for low focal length objective lens. Or Ray diagram For correct derivation For correct definition For correct graph 3m K 1m 1m 2m 2m 1m 1m 1m 1m 1m -5- = + = +1 = 1-- At X-axis intercept, m= 0 = - +1 m = 1-- m = - +1 v=f 29. For correct circuit diagram 1m 2m For correct graph 1m For correct definition + (Cut off State: Transistor will be in cut off state when output current (Ic) is zero. Transistor does not conduct. Active state : When there is some current (Ic) in collector-emitter circuit , then the transistor is said to be in active state) When transistor is used as a switch it does not remain in active state. 1m OR C1 is output of AND gate having and B as its two inputs. (with waveform) 1m C2 is output of AND gate having A and as its two inputs (with waveform) 1m The output Y is the output of an NOR gate having C1 and C2 as its two inputs (with waveform) 2m Output (Y) only when both the inputs A and B are alike. 1m

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Additional Info : CBSE Class XII Pre Board II Solved Question Paper 2014 Physics
Tags : CBSE Pre Board Paper II 2014 Physics with Solutions, KV IIT Chennai Prelims, Specimen Question Paper, science solved sample mock guess question paper, cbse class XII syllabus, cbse class 12 previous years model papers, kendriya vidyalaya kv iit chennai, iit madras, cbse pre boards, prelims preliminary exams, cbse specimen / guess / mock papers / books, cbse india portal, central board for secondary education, answer keys, top schools, cbse question bank, cbse model test papers with answers, solved question papers of cbse last year, previous years papers with solutions, free download pdf online cbse paper, cbse syllabus, pattern, dates notification, application forms, india cbse board sample last 10 years, clat important questions preparation, how to prepare, 2015, 2014.

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