12th PUBLIC PHYSICS - KEY ANSWERS - MARCH … · B.KANNAN M.Sc., B.Ed., 1 12th PUBLIC PHYSICS - KEY...
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B.KANNAN M.Sc., B.Ed., 1 12th PUBLIC PHYSICS - KEY ANSWERS - MARCH-2018 PART-I Q.NO A-TYPE Q.NO B-TYPE 1 b uncontrolled fission reaction 1 d intensity of incident radiation 2 a in a direction bisecting angle ACB 2 a 10.7 MHz 3 d Scanning 3 a immobile positive ions 4 d α-paricles 4 a capacitor 5 c zero 5 a 0.66 milli coulomb 6 c an ON switch 6 a 7 a 0.66 milli coulomb 7 b contracts 8 d intensity of incident radiation 8 c conservation of energy 9 a diffraction pattern becomes narrower and crowded together 9 a in a direction bisecting angle ACB 10 a the velocity of the particle 10 b uncontrolled fission reaction 11 c neither a net force nor a torque 11 a 26 Fe 59 12 b 0 , 0 12 c 10 -27 kgms -1 13 b 13 a 14 a 10.7 MHz 14 b/c m 2 V -1 s -1 or Cskg -1 15 d 1 15 c neither a net force nor a torque 16 b Transverse 16 b 0 , 0 17 d E -1 17 d 1 18 d absorbs green light 18 c an ON switch 19 b/c m 2 V -1 s -1 or Cskg -1 19 a high specific resistance 20 c conservation of energy 20 b phenomenon of conversion of kinetic energy into radiation 21 a capacitor 21 d 9 minutes 22 b phenomenon of conversion of kinetic energy into radiation 22 a diffraction pattern becomes narrower and crowded together 23 a 23 d absorbs green light 24 c 10 -27 kgms -1 24 d E -1 25 a 25 b 26 a immobile positive ions 26 c zero 27 a 26 Fe 59 27 a the velocity of the particle 28 a high specific resistance 28 d scanning 29 b contracts 29 b transverse 30 d 9 minutes 30 d α-paricles www.Padasalai.Net www.TrbTnpsc.com http://www.trbtnpsc.com/2014/12/plus-two-12th-old-public-exam-govt.html www.Padasalai.Net www.Padasalai.Net www.Padasalai.Net www.Padasalai.Net www.Padasa www.Padasalai.Net www.Padasalai.Net www.Padasalai.Net www.Padasalai.Net www.Padasa www.Padasalai.Net www.Padasalai.Net www.Padasalai.Net www.Padasalai.Net www.Padasa www.Padasalai.Net www.Padasalai.Net www.Padasalai.Net www.Padasalai.Net www.Padasa www.Padasalai.Net www.Padasalai.Net www.Padasalai.Net www.Padasalai.Net www.Padasala www.Padasalai.Net www.Padasalai.Net www.Padasalai.Net www.Padasalai.Net www.Padasala www.Padasalai.Net www.Padasalai.Net www.Padasalai.Net www.Padasalai.Net www.Padasala www.Padasalai.Net www.Padasalai.Net www.Padasalai.Net www.Padasalai.Net www.Padasala
Transcript of 12th PUBLIC PHYSICS - KEY ANSWERS - MARCH … · B.KANNAN M.Sc., B.Ed., 1 12th PUBLIC PHYSICS - KEY...
B.KANNAN M.Sc., B.Ed.,
1
12th PUBLIC PHYSICS - KEY ANSWERS - MARCH-2018
PART-I
Q.NO A-TYPE Q.NO B-TYPE 1 b uncontrolled fission reaction 1 d intensity of incident radiation
2 a in a direction bisecting angle ACB 2 a 10.7 MHz
3 d Scanning 3 a immobile positive ions
4 d α-paricles 4 a capacitor
5 c zero 5 a 0.66 milli coulomb
6 c an ON switch 6 a
7 a 0.66 milli coulomb 7 b contracts
8 d intensity of incident radiation 8 c conservation of energy
9 a diffraction pattern becomes narrower and crowded together
9 a in a direction bisecting angle ACB
10 a the velocity of the particle 10 b uncontrolled fission reaction
11 c neither a net force nor a torque 11 a 26Fe59
12 b 0 , 0 12 c 10-27 kgms-1
13 b
13 a
14 a 10.7 MHz 14 b/c m2V-1s-1 or Cskg-1
15 d 1 15 c neither a net force nor a torque
16 b Transverse 16 b 0 , 0
17 d E-1 17 d 1
18 d absorbs green light 18 c an ON switch
19 b/c m2V-1s-1 or Cskg-1 19 a high specific resistance
20 c conservation of energy 20 b phenomenon of conversion of kinetic energy into radiation
21 a capacitor 21 d 9 minutes
22 b phenomenon of conversion of kinetic energy into radiation
22 a diffraction pattern becomes narrower and crowded together
23 a
23 d absorbs green light
24 c 10-27 kgms-1 24 d E-1
25 a
25 b
26 a immobile positive ions 26 c zero
27 a 26Fe59 27 a the velocity of the particle
28 a high specific resistance 28 d scanning
29 b contracts 29 b transverse
30 d 9 minutes 30 d α-paricles
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B.KANNAN M.Sc., B.Ed.,
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Important Note:
1. 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.
2. Answers written only in BLACK or BLUE should be evaluated.
3. For graphical representation, X and Y variables must be mentioned . If not , reduce ½ mark.
4. Marks should be given to the unit, only if the answer is correct for problems.
PART-II
Q.No Description MARK TOTAL 31 Coulomb’s law - Correct statement
Mere equation F =
3 1
3
32 Polar molecule – correct definition Any one example
2 1
3
33 Electrical resistivity – correct definition Unit = Ohm meter
2 1
3
34 Rt = Ro(1+αt) Substitution Rt = 14 Ω (correct answer +unit)
1 1 ½ +½
3
35 Emf and potential difference ( any two 2x1½) 3 3
36 Ampere’s circuital law – correct statement (or)
= µo Io
3 1
3
37 e = -Blv substitution e =-0.0164 V (correct answer +unit)
1 1 ½ +½
3
38 Q – factor – correct statement (or)
Q =
(or) Q =
3 1
3
39 Huygen’s principle – correct statement (2x1½) 3 3
40 rn = (or) λ =
substitution λ = 5400 Ȧ (correct answer +unit)
1 1 ½ +½
3
41 Correct conditions – Achieve laser action 3 3
42 2d sin = nλ substitution λ max = 5.64 x 10 -10 m(correct answer +unit)
1 1 ½ +½
3
43 Any 3 uses of Electron microscope (3x1) 3 3
44 Any 3 properties of β – rays 3 3
45 Correct definition - Pair production Annihilation of matter
1½ 1½
3
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B.KANNAN M.Sc., B.Ed.,
3
46 Proper simplification using Boolean Algebra 3 3
47 Any 3 advantages of negative feedback (3 x 1=3) 3 3
48 De Morgan’s theorems (2 x 1½) (OR) Mere equations (1+1)
3 2
3
49 Proper circuit diagram – OR gate using diodes 3 3
50 Any 3 advantages of digital communication 3 3
PART-III
57 Electric lines of forces : Any 5 properties of electric lines of forces (5x1) 5 5
52 Daniel cell Diagram Construction Working Mentioning – cannot supply steady current for long time Emf = 1.08 V
1 1 2 ½ 1/2
52 Superconductors : Any 5 applications of Superconductors (5x1) 5 5
54 B =
substitution and calculation B= 9.9x 10-5 T (correct answer +unit)
2 2 ½+½
5
55 Mutual Induction of two long Solenoid Diagram Explanation Upto ɸ2=MI1
upto M =
1 1 2 1
5
56 Radius of nth Dark ring in Newton’s Experiment: Diagram Explanation
Upto 2t =
Condition for darkness 2t = nλ
rn =
1 1 1 1 1
5
57 Spectral series of Hydrogen atom Explanation of five series Formula (or) Mere mentioning the names of spectral series only
2 ½ 2 ½ 2
5
58 Einstein’s photo electric equation: Quantum theory – mentioning Interaction between photon and single electron of a metal surface Explanation - Utilization of energy of photon in two ways hʋ = W + ½ mv2 if the electron does not lose energy by internal collisions the entire energy ( hʋ- w ) will be exhibited as kinetic energy of the electron
½ 1 1 1 ½
5
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B.KANNAN M.Sc., B.Ed.,
4
hʋ = W + ½ mvmax2 (or) h(ʋ-ʋo) = ½ mvmax
2 1
59 Problem
l = lo
substitution v = 0.423 x 108 ms-1 (correct answer +unit)
2 2 1
5
60 Compulsory Problem a.N = Noe-λt
λ =
substitution t = 5.022 days (correct answer +unit ) (OR) b. reactant mass = 4.4 MeV Product mass = 28 MeV Mass defect E = 23.6 MeV
1 1 2 1 1½ 1½ 1 1
5
61 α and β relation:
Current gain in CB Mode α =
Current gain in CE Mode β =
α =
upto β =
(or) α =
1 1 1 2
5
62 Radar Principle Any 4 applications of radar (4x1)
1 4
5
PART - IV
63 Electricfield – Axial line Electric dipole definition Diagram Explanation
E1 =
(along BP)
E2 =
(along PA)
E = E1 + (-E2 )
Upto E =
(along BP)
P =q x 2d E acts in the direction dipolemoment
1 1 1 1 1 1 2 1 1
10
64 Force acting on a current carrying conductor placed in a magnetic field: Diagram
2
10
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B.KANNAN M.Sc., B.Ed.,
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Explanation I = nAeVd Il = - nAevd f = -e (vd x B) F = Nf F = - nAlevd x B F = Il x B
2 1 1 1 1 1 1
65 AC Generator – single phase Diagram Principle Explanation of 4 parts – (4x1/2 ) (mere mentioning the parts – 1 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
2 1 2 1 1 1 1 1
10
66 Types of Spectra Definition of Emission spectrum Explanation of continuous spectrum Explanation of line spectrum Explanation of band spectrum Definition of absorption spectrum Explanation of continuous absorption spectrum Explanation of line absorption spectrum Explanation of band absorption spectrum (OR) Mentionin the kind of Emission and Absorption spectrum(1+1)
2 1 1 1 2 1 1 1
10
67 Radius of nth orbit in Bohr atom model Postulates (2x1) Explanation
Upto =
L =
= m
=
Upto arriving the following relation
rn =
for hydrogen atom Z = 1
rn =
2 1 2 1 1 1 1 1
10
68 BainBridge Mass Spectrometer Diagram Accurate determination of atomic masses Description
Eq = BqV (or) V =
Explanation of effect of magnetic field B’ in the chamber B’qV = mv2 / r
2 1 2 1 1 1
10
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B.KANNAN M.Sc., B.Ed.,
6
m =
and Measurement of R 1+1
69 Bridge rectifier Definition for rectification Circuit diagram Construction Explanation of positive half cycle Explanation of negative half cycle Current flows through RL in the direction, during both half cycles of input a.c signal Efficiency 81.2% Input and output waveforms
1 2 1 1 1 1 1 1+1
10
70 Superheterodyne AM receiver Correct block diagram Explanation R.F Amplifier Mixer and local oscillator IF amplifier Detector AF amplifier
4 1 2 1 1 1
10
PREPARED BY
B.KANNAN M.Sc., B.Ed., BT ASST IN ( SCIENCE ) GHSS, MUDUR-631 003 VELLORE DT
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