12th PHYSICS KEY ANSWERS MARCH-2016 PART-I

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1 th PHYSICS KEY ANSWERS MARCH-06 PART-I Q.NO A-TYPE Q.NO B-TYPE c AB c A plane surface passing through the centre of the electric dipole and perpendicular to the axis of the electric dipole b P d Zero b.6x0 - m d Infinite resistance 4 c Sin - (/ ) 4 b Twice the signal freqency c 0. b Power is transmitted in a direction 0.69 perpendicular to both the fields 6 b Twice the signal freqency 6 c 000 W 7 a downwards 7 c AB 8 b Room heater 8 c Sin - (/ ) 9 c 0. 9 b Zero and maximum 0 b Electric field decreases 0 d Conservation of energy b.7 V c 0. minutes 0.69 a Phenomenon of conversion of radiation into kinetic energy b Power is transmitted in a direction perpendicular to both the fields c m c Sommerfeld 4 a Collision 4 c 0. a Pure line spectrum a Pure line spectrum 6 b Absorbs green light 6 c Ionospheric propagation 7 b A to B till the potentials become 7 b P equal 8 c Ionospheric propagation 8 c m 9 a Phenomenon of conversion of 9 a Downwards radiation into kinetic energy 0 c A plane surface passing through the centre of the electric dipole and perpendicular to the axis of the electric dipole 0 b A to B till the potentials become equal c 7.9 MeV b Electric field decreases d Infinite resistance a Collision c 000 W b Room heater 4 c Sommerfeld 4 c 600 J a C N - m - a Zero 6 d Zero 6 b.6x0 - m 7 a Zero 7 a C N - m - 8 c 600 J 8 b Absorbs green light 9 b Zero and maximum 9 b.7 V 0 d Conservation of energy 0 c 7.9 MeV B.KANNAN M.Sc., B.Ed., Ph:

2 Important Note:. For answers in Part II, Part-III, and Part- IV like reasoning, explanation, narration,description and listing the points, students may write in their own words but without changing the concepts and without skipping any point.. Answers written only in BLACK or BLUE should be evaluated.. For graphical representation, X and Y variables must be mentioned. If not, reduce mark. 4. Marks should be given to the unit, only if the answer is correct for problems. PART-II Q.No Descrbtion MARK TOTAL Gauss s law Correct definition (or) ɸ= q εo Lines of force Any properties (x) Mobility correct definition Unit : m V - s - 4 r=( E V V r= 0.0Ω (correct answer +unit) + Temperature Co-effienct of Resistance- Correct definition 6 B = μoi πa B = x0 - T (correct answer +unit) + 7 Three methods of producing induce emf(x) 8 e = -Blv e = V (correct answer +unit) + 9 Write any differences between interference and diffraction (x) 40 Any uses of polaroids (x) 4 Moseley s law correct definition Equation : ν α Z 4 Eq = mg (or) q = mgd V q=ne / / q = 6.7x0-0 C and n=4 (correct answer +unit) + 4 Any uses of Electron microscope (x) 44 β decay correct definition example 4 Any uses of Nuclear reactor(x) 46 Proper circuit diagram for voltage regulator (without labeling only marks) B.KANNAN M.Sc., B.Ed., Ph:

3 47 A A f = +Aβ β = 0.0 (correct answer +unit) + 48 Correct statement 49 Any uses of ICs (x) 0 Skip distance correct statement If sky wave propagation and fixed frequency not mentioned reduce mark ( +) PART-III a) C = εoa d C =.86x0 - F U= CV U =.x0-6 J (or) b) U = 4πεor q +q q +q q ) U = - 0. J (correct answer +unit) + Any applications of Superconductors (x) Law m m I m m4 t m α It (or) m α q 4 Any special features of Magnetic Lorentz force (x) Circuit diagram e = Eo sinωt e = ir upto i = Io sinωt To mention the phase angle between the voltage and the current 6 I = (a) I (a) Imax = (a+a) Imin (a a) Imax : Imin : : 8 : 49 7 Any properties of Canal rays (x) 8 Photo electric effect definition Four laws (4x) 4 B.KANNAN M.Sc., B.Ed., Ph:

4 9 Time Dilation: to t = v c t > to lengthened factor Example v c 60 Mass of reactant = amu Mass of product = amu Mass defect = amu amu = 9 MeV Energy released = 4.78 MeV 6 Half wave Rectifier Circuit diagram Waves diagram Unidirectional pulsating output is obtained Efficiency definiftion Efficiency 40.6 % 6 Optical fibre If not mentioned coherent light and Principle : Total internal reflection reduce mark for each Advantages (4x) / 4 6 Electricfield Axial line Electric dipole definition q E = (along BP) 4πεo (r d) q E = (along PA) 4πεo (r+d) E = E + (-E ) Upto E = 4πεo p r (along BP) PART - IV 0 P =q x d E acts in the direction dipolemoment 64 Cyclotron 0 4 B.KANNAN M.Sc., B.Ed., Ph:

5 Principle Construction Working BqV = mv / r T = π m / Bq ( or ) ν = Bq / πm Limitations (any ) 6 AC Generator single phase Principle of 4 parts (4x/ ) (mere mentioning the parts mark Direction of induced current given by Flemming Right Hand rule First half cycle Second half cycle e = Eo sinωt ; Eo= NBAω Output sine wave form 66 Raman effect Raman effect explanation (x) of stoke s and Anti-stoke s lines with respect to frequency of Raman effect (x) for ν = νo-νs ν is positive for stoke line ν is negative for Anti-stoke line Intensity of stoke line is always greater than antistoke line 67 J.J Thomson Experiment Derivation upto V = E B t = l v y = Y=k y e Ee m = ye m Kl B l v 68 BainBridge Mass Spectrometer Accurate determination of atomic masses Description Eq = BqV (or) V = E B of effect of magnetic field B in the chamber B qv = mv / r m = BB qr and Measurement of R E Non-Inverting Operational Amplifier Operational Amplifier correct definition B.KANNAN M.Sc., B.Ed., Ph:

6 A v = Vout V A = VA Rin Rf+Rin Vout VA Vout (or) Vout VA = + Rf Rin (or) A v = + Rf Rin = = Rf+Rin Rin Vout = ( + Rf Rin ) Vin Input and output voltages are Inphase 70 Monochrome TV Transmitter Block diagram (0 x ) 0 PREPARED BY B.KANNAN M.Sc., B.Ed., BT ASST IN ( SCIENCE ) GHSS, MUDUR-6 00 VELLORE DT 6 B.KANNAN M.Sc., B.Ed., Ph:

HALF-YEARLY EXAM PHYSICS KEY ANSWER KEY DECEMBER-2018 PART-I

et et HALF-YEARLY EXAM PHYSICS KEY ANSWER KEY DECEMBER-08 SL.NO et et et et et et et et et et et et et et et c) both a net force and a torque d).8ω b) m 4 a) 0ᵒC b) net reactance is zero 6 a) Increased