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Comprehensive Guidelines
For Academic Excellence
in
Comprehensive Guidelines
For Academic Excellence
in
PHYSICS
for
PGT's
2007
300 Copies, 2007Chief Advisor
Guidance
Rina Ray
Prof. N. K. Sehgal
Dr. Charu Varma
Mr.C.B. Verma
Mr. Sher Singh . . .
Mr. Giri Bhardwaj e
Ms. Sneh Lata . . ., . . . . .,
Ms. Sukhda . . ., . . . .,
Dr. Santosh Verma . . .,
,
Reader Physics, Hansraj College, DU.
Lecturer (Science), PSTE, DIET Pitampura
Retd. Principal
H O D , Physics
Navyug School, Lodhi Road.
D.T.E.A., Sr.S.S., Laxmi Bai Nagar.
Science Counsellor, Pitampura Sci nce Center.
P G T Physics, G G S S S No. 1 Tilak Nagar.
P G T Physics, G S K V B-3 Paschim Vihar.
P G T Physics, G.S.V. Rani Bagh.
Secretary, (Education) GNCT of DelhiChairperson, SCERT
Sh. B.N. BajpaiDr. Pratibha Sharma
Course Directors
Material Development Team
Power Point Development Team
Dr. Charu VarmaMr M.M. Roy
Lecturer (Science),PSTE, DIET Pitampura.Lecturer, DRU, DIET Ghumanhera.
Mr. R. Ranga Rajan . . .
Mr. Rakesh Bhardwaj . . .
Prof. N. K. Sehgal
Mr. Sher Singh . . .
Mr. R. Ranga Rajan . . .,
Mr. Rakesh Bhardwaj . . .
H O D , Physics
H O D , Physics
M.A.P.S., Pitampura, Delhi
Reader Physics, Hansraj College, DU.
H O D , Physics
Navyug School, Lodhi Road.
H O D Physics
D.T.E.A., Sr.S.S., Laxmi Bai Nagar.
H O D , Physics
M.A.P.S., Pitampura, Delhi
Educational Stores, 1/1978, Modern Shahdara, Shahdara, Delhi-110032
Published by Mukesh Yadav, Publication officer, State Council of Educational Research & Training, New Delhi on
behalf of SCERT and printed at
(ii)
Quality education has always been a major concern for the educationalists. Inthe advent of Globalization, Liberalization and Economic Reforms, there is aconstant need to restructure the system and make it more flexible and pragmaticand in tune with changing manpower requirements. To keep pace with thechanging scenario, NCERT and CBSE have brought in required changes in theschool curriculum and learners' assessments at all levels. There is a need to orientour teachers about these changes in the textbooks and the latest - technologies foreffective implementation in the teaching learning processes.
Teachers' Manual developed by SCERT and DIET Faculty in differentsubjects at Senior Secondary level is an attempt to meet this objective. TheManuals are based as per the needs of the teachers which include grey areas andhard spots in different subjects meant for quality improvement. The objective isalso to make the teaching learning process interactive and enabling students tomove beyond the textbooks, which is one of the concerns of National CurriculumFramework-2005. It will also give an insight to teachers about different activities,projects, assignments, case- studies, application based questions on new CBSEpattern to develop critical thinking and problem solving abilities. These manualshave been developed through workshop mode incorporating the feedback byteachers on new textbooks by NCERT.
There have been remarkable developments in the Government School resultsof classes X and XII. The results of class X have gone up by 29% in last two years.In Science, the result of objective type questions (MCQ) was 100%, which iscommendable. The aggregate result of class XII (after compartment) is competingwith the results of public schools, which is phenomenal. The credit goes to variousinitiatives taken by Directorate of Education, SCERT/DIET for qualityimprovement in Government Schools of Delhi. This has also been possible due tothe intensive training in content and methodology in the recent past and by thecontinuous monitoring and follow -up by the officials at all levels.
I acknowledge a deep sense of gratitude to the team of Advisors and Expertswho have provided their valuable suggestions in preparing these Manuals andthanks are also extended to the Editors, Co-ordinators, team of subject experts, allSCERT/DIET faculty (academic and administration), publication-division whohave immensely contributed in completing this assignment.
Preface...
(iii)
subject experts, all SCERT/DIET faculty (academic and administration),publication-division who have immensely contributed in completing thisassignment.
I sincerely hope that these Teachers' Manuals will enable our teachers to makethe class room processes more interactive and activity-based for enhancement ofoverall performance of children in Government Schools.
Your suggestions and comments regarding the Teachers' Manual arewelcome.
B.N Bajpai(Director)SCERT, Varun Marg,Defence ColonyNew Delhi
(iv)
CHAPTER-1
C.B.S.E SYLLABUS
PHYSICS (Code No. 042)
Senior Secondary stage of school education is a stage of transition from general education to
discipline-based focus on curriculum. The present updated syllabus keeps in view the rigour and depth
of disciplinary approach as well as the comprehension level of learners. Due care has also been taken
that the syllabus is not heavy and is at the same time, comparable to the international standards. Salient
features of the syllabus include:
• Emphasis on basic conceptual understanding of the content
• Emphasis on use of SI units, symbols, nomenclature of physical quantities and
formulations as per international standards.
• Providing logical sequencing of units of the subject matter and proper placement ofconcepts with their linkage for better learning.
• Reducing the curriculum load by eliminating overlapping of concepts/ content with in thediscipline and other disciplines.
• Promotion of process-skills, problem-solving abilities and applications of Physicsconcepts.
Besides, the syllabus also attempts to
• strengthen the concepts developed at the secondary stage to provide firm
foundation for further learning in the subject.
• expose the learners to different processes used in Physics-related industrialand technological applications.
• develop process-skills and experimental, observational, manipulative,decision making and investigatory skills in the learners.
• promote problem solving abilities and creative thinking in learners.
• develop conceptual competence in the learners and make them realize andappreciate the interface of Physics with other disciplines.
(1)
COURSE STRUCTURE
Class XII - Theory
One Paper Time: 3 Hours 70 Marks
Total 70
Unit I: Electrostatics (Periods 25)
Unit I Electrostatics 08
Unit II Current Electricity 07
Unit III Magnetic effect of current & Magnetism 08
Unit IV Electromagnetic Induction andAlternating current 08
Unit V Electromagnetic Waves 03
Unit VI Optics 14
Unit VII Dual Nature of Matter 04
Unit VIII Atoms and Nuclei 06
Unit IX Electronic Devices 07
Unit X Communication Systems 05
• Electric Charges; Conservation of charge, Coulomb's law-force between two point charges,
forces between multiple charges; superposition principle and continuous charge distribution.
Electric field, electric field due to a point charge, electric field lines; electric dipole, electric field
due to a dipole; torque on a dipole in uniform electric field. Electric flux, statement of Gauss's
theorem and its applications to find field due to infinitely long straight wire, uniformly charged
infinite plane sheet and uniformly charged thin spherical shell (field inside and outside). Electric
potential, potential difference, electric potential due to a point charge, a dipole and system of
charges; equipotential surfaces, electrical potential energy of a system of two point charges and of
electric dipole in an electrostatic field. Conductors and insulators, free charges and bound charges
inside a conductor. Dielectrics and electric polarisation, capacitors and
(2)
capacitance, combination of capacitors in series and in parallel, capacitance of a parallel plate capacitor
with and without dielectric medium between the plates, energy stored in a capacitor. Van de Graaff
generator.
Electric current, flow of electric charges in a metallic conductor, drift velocity, mobility and their
relation with electric current; Ohm's law, electrical resistance, V-I characteristics(linear and
non-linear), electrical energy and power, electrical resistivity and conductivity. Carbon resistors,
colour code for carbon resistors; series and parallel combinations of resistors; temperature
dependence of resistance.
Internal resistance of a cell, potential difference and emf of a cell, combination of cells in series
and in parallel. Kirchhoff's laws and simple applications. Wheatstone bridge, metre bridge.
Potentiometer - principle and its applications to measure potential difference and for comparing
emf of two cells; measurement of internal resistance of a cell.
Concept of magnetic field, Oersted's experiment. Biot - Savart law and its application to current
carrying circular loop. Ampere's law and its applications to infinitely long straight wire, straight
and toroidal solenoids. Force on a moving charge in uniform magnetic and electric fields.
Cyclotron. Force on a current-carrying conductor in a uniform magnetic field. Force between two
parallel current-carrying conductors-definition of ampere. Torque experienced by a current loop
in uniform magnetic field; moving coil galvanometer-its current sensitivity and conversion to
ammeter and voltmeter. Current loop as a magnetic dipole and its magnetic dipole moment.
Magnetic dipole moment of a revolving electron. Magnetic field intensity due to a magnetic
dipole (bar magnet) along its axis and perpendicular to its axis. Torque on a magnetic dipole (bar
magnet) in a uniform magnetic field; bar magnet as an equivalent solenoid, magnetic field lines;
Earth'smagnetic field and magnetic elements.
Unit II: Current Electricity (Periods 22)
Unit III: Magnetic Effects of Current and Magnetism (Periods 25)
•
•
(3)
Unit IV: Electromagnetic Induction andAlternating Currents (Periods 20)
Unit V: Electromagnetic waves (Periods 4)
Unit VI: Optics (Periods 30)
•
•
•
Electromagnetic induction; Faraday's law, induced emf and current; Lenz's Law, Eddy currents.
Self and mutual inductance. Need for displacement current.
Alternating currents, peak and rms value of alternating current/voltage; reactance and
impedance; LC oscillations (qualitative treatment only), LCR series circuit, resonance; power in
AC circuits, wattless current.AC generator and transformer.
Electromagnetic waves and their characteristics (qualitative ideas only). Transverse nature of
electromagnetic waves. Electromagnetic spectrum (radio waves, microwaves, infrared, visible,
ultraviolet, Xrays, gamma rays) including elementary facts about their uses.
Reflection of light, spherical mirrors, mirror formula. Refraction of light, total internal reflection
and its applications, optical fibres, refraction at spherical surfaces, lenses, thin lens formula, lens-
maker's formula. Magnification, power of a lens, combination of thin lenses in contact.
Refraction and dispersion of light through a prism. Scattering of light - blue colour of the sky and
reddish appearance of the sun at sunrise and sunset. Optical instruments: Human eye, image
formation and accommodation, correction of eye defects (myopia, hypermetropia, presbyopia
and astigmatism) using lenses. Microscopes and astronomical telescopes (reflecting and
refracting) and their magnifying powers. Wave optics: wave front and Huygens' principle,
reflection and refraction of plane wave at a plane surface using wave fronts. Proof of laws of
reflection and refraction using Huygens' principle. Interference, Young's double slit experiment
and expression for fringe width, coherent sources and sustained interference of light. Diffraction
due to a single slit, width ofcentral maximum. Resolving power
of microscopes and astronomical telescopes. Polarisation, plane polarised light; Brewster's law,
uses of plane polarised light and Polaroids.
(4)
Unit VII: Dual Nature of Matter and Radiation (Periods 8)
Unit VIII:Atoms & Nuclei (Periods 18)
Unit IX: Electronic Devices (Periods 18)
Unit X: Communication Systems (Periods 10)
•
•
•
•
Dual nature of radiation. Photoelectric effect, Hertz and Lenard's observations; Einstein's
photoelectric equation-particle nature of light. Matter waves-wave nature of particles, de Broglie
relation. Davisson-Germer experiment.
Alpha-particle scattering experiment; Rutherford's model of atom; Bohr model, energy levels,
hydrogen spectrum. Composition and size of nucleus, atomic masses, isotopes, isobars; isotones.
Radioactivityalpha, beta and gamma particles/rays and their properties; radioactive decay law.
Mass-energy relation, mass defect; binding energy per nucleon and its variation with mass
number; nuclear fission and fusion.
Semiconductors; semiconductor diode I-V characteristics in forward and reverse bias,diode as a
rectifier; I-V characteristics of LED, photodiode, solar cell, and Zener diode;Zener diode as a
voltage regulator. Junction transistor, transistor action, characteristics of a transistor; transistor as
an amplifier (common emitter configuration) and oscillator. Logic gates (OR, AND, NOT,
NAND and NOR). Transistor as a switch.
Elements of a communication system (block diagram only); bandwidth of signals (speech, TV
and digital data); bandwidth of transmission medium. Propagation of electromagnetic waves
in the atmosphere, sky and space wave propagation. Need for modulation. Production and
detection of an amplitude-modulated wave.
(5)
CLASS XII - PRACTICALS
Every student will perform 10 experiments (5 from each section) & 8 activities (4 from each section)
during the academic year.
One experiment from any one section 8 Marks
Two activities (one from each section) (4+4) 8 Marks
Practical record (experiments & activities) 6 Marks
Viva on experiments & activities 5 Marks
1. To determine resistance per cm of a given wire by plotting a graph of potential difference versus
current.
2. To find resistance of a given wire using metre bridge and hence determine the specific resistance
of its material.
3. To verify the laws of combination (series/parallel) of resistances using a metre bridge.
4. To compare the emf of two given primary cells using potentiometer.
5. To determine the internal resistance of given primary cell using potentiometer.
6. To determine resistance of a galvanometer by half-deflection method and to find its figure of
merit.
7. To convert the given galvanometer (of known resistance and figure of merit) into an ammeter and
voltmeter of desired range and to verify the same.
8. To find the frequency of the a.c. mains with a sonometer.
Two demonstration experiments must be performed by the teacher with
participation of students. The students will maintain a record of these demonstration experiments.
B. Evaluation Scheme for Practical Examination:
Record of demonstration experiments & Viva based on these experiments 3 Marks
Total 30 Marks
•
•
•
•
•
SECTION A
Experiments
(6)
Activities
1. To measure the resistance and impedance of an inductor with or without iron core.
2. To measure resistance, voltage (AC/DC), current (AC) and check continuity of a given circuit
using multimeter.
3. To assemble a household circuit comprising three bulbs, three (on/off) switches, a fuse and a
power source.
4. To assemble the components of a given electrical circuit.
5. To study the variation in potential drop with length of a wire for a steady current.
6. To draw the diagram of a given open circuit comprising at least a battery, resistor/rheostat, key,
ammeter and voltmeter. Mark the components that are not connected in proper order and correct
the circuit and also the circuit diagram.
4. To find the focal length of a concave lens, using a convex lens.
5. To determine angle of minimum deviation for a given prism by plotting a graph between angle of
incidence and angle of deviation.
6. To determine refractive index of a glass slab using a travelling microscope.
7. To find refractive index of a liquid by using (i) concave mirror, (ii) convex lens and plane mirror.
8. To draw the I-V characteristic curve of a p-n junction in forward bias and reverse bias.
9. To draw the characteristic curve of a zener diode and to determine its reverse break down voltage.
10. To study the characteristics of a common - emitter npn or pnp transistor and to find out the values
of current and voltage gains.
SECTION B
Experiments
1. To find the value of v for different values of u in case of a concave mirror and to find the focal
length.
2. To find the focal length of a convex lens by plotting graphs between u and v or between l/u and l/v.
3. To find the focal length of a convex mirror, using a convex lens.
(7)
Activities
1. To study effect of intensity of light (by varying distance of the source) on an L.D.R.
2. To identify a diode, an LED, a transistor, and IC, a resistor and a capacitor from mixed collection
of such items.
3. Use of multimeter to (i) identify base of transistor. (ii) distinguish between npn and pnp type
transistors. (iii) see the unidirectional flow of current in case of a diode and an LED. (iv) check
whether a given electronic component (e.g. diode, transistor or I C) is in working order.
4. To observe refraction and lateral deviation of a beam of light incident obliquely on a glass slab.
5. To observe polarization of light using two Polaroids.
6. To observe diffraction of light due to a thin slit.
7. To study the nature and size of the image formed by (i) convex lens (ii) concave mirror, on a
screen by using a candle and a screen (for different distances of the candle from the lens/mirror).
8. To obtain a lens combination with the specified focal length by using two lenses from the given
set of lenses.
(8)
(9)
CHAPTER - 2
CHAPTER - 3 a
Unsolved Sample Papers
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CHAPTER - 3 b
Solved Sample Papers withMarking Scheme
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CHAPTER-4
LIST OF LAB APPRATUS AND INSTRUMENTS NEEDED BY THE
STUDENTS ( XI & XII)
(a.) Non Consumable
•
• S
•
•
•
Meter scale and half meter scale
pherical and Cylindrical Body
Beaker
Vernier Calliper
Screw gauge
• Spherical surface-mirror (convex and concave)
• Physical balance
• Parallogram Law of vectors apparatus (Grave's sand apparatus)
• Spherical bob
• Stop clock
• Iron stand
• Apparatus for experiment on friction ( Horizontal and Inclined Plane)
• Burette
• Thermometer
• Measuring tape
• Spherical balls
• Young's modulus apparatus
• Helical spring
• Co-efficient of viscosity apparatus
• Calorimeter
• Sonometer
• Tuning fork
• Resonance tube apparatus
• Fortin's barometer
• Bi-metallic strips.
• Microscope (Travelling)
(70)
(71)
••••••••• a••••••••••
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Black body
Different Masses
Wooden blocks
Dry cells
Battery eliminator
Accumulator
D.C. Ammeter
D.C. Voltmeter
D.C. G lvanometer
Rheostat
Resist nce box
Single Plug Key
Two way Plug Key
Resist nce coil
Meter bridge
Post Office Box
Leclanche cell
Daniel cell
Potentiometer
Inductor
A.C. Voltmeter
A. C. ammet r
Multimeter
Optical ench
Concave Mirror
Convex Mirror
Convex
Convace
Glass prism
Glass slab
a
a
e
B
Lens
Lens
Concave Lens
Convex Lens
Glass slab
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Drawing board
p-n junction diode
Tra sistor npn and pnp
Re ist rs of high resistance
Integrated circu t
Capacitor
Choke coil
Polaroids
Screen
Bar pendulum
LASER
Photo transistor
Telescope
Electric lamps of different powers
Rubber pads
Bar magnet
Slinky
Plane Mirror
Fuse
Electrically maintained tu fork
Compass needle
Magnifying glass
Logic gates
Complete list of apparatus is also available in science branch.
n
s o
i
ning
Note :
(72)
(b.) Consumable Items
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Awl
u
c
White paper
Capillary tube
pins
Insulating wire
Iron filing
Switches
Cut outs
Gum
Dusters
Ammonium Chloride
Copper Sulphate
Sodium Chloride
Sulph ric Acid
Sand Paper
Glycerine
Hydro hloric Acid
Thread
Candle
Match box
Connecting wire
(73)
CHAPTER-5
TEN COMMANDMENTS FOR STUDENTSTO SCORE GOOD MARKS IN CLASS XII
1. Identify the areas of your interest and having previous knowledge and study these topics 100%without leaving any pot-holes.
2. Prepare the chapters having more weight age of the areas of your interest and previous knowledgefirst and do them with an eye on a 5 mark question.
3. Instead of leaving the topics like E.M.Waves, Principles of Communication understand toexpress all definitions, interpretation of figures, Advantages and disadvantages of variousdevices andApplications etc.
4. Do the super hit questions/topics like Cyclotron, A.C.Generator, Young's experiment, Gauss'stheorem, Wheatstone's bridge, potentiometer etc.., many times before the examination, so thatyou do not flop during the examination because of the tilted nature of a question.
)
5. Do all the worked examples and the graphs with their Interpretation from NCERT during yourpreparation.
6. Go to the examination hall with a positive frame of mind - particularly on the Physicsexamination day, at least half an hour before without any books and please do not discuss anyquestion with anyone in this period.
7. Start the answer script with the best known question and go in an order-ascending or descendingand do the best known questions and then come on the second round doing the rest of thequestions. Be precise with your answer.
(See attached List of 15 topics
8. In case you are not having good Interpretation skill, try to develop the same. If you are stilldoubtful, first do the best known five mark questions and try to create a good impression in theminds of the paper checker.
9. When you approach the numerical question always understand the question, recall the knownconcept of the question and never try to list the formula and substitute the values. The first linethat you write is always an important one as it is to send the signal to the examiner. Soconceptualize the problem, success will be yours.
10. Present the paper neatly and legibly without cutting and leaving space for anything that you planto do later, since there will not be any time to do later. If you happen to cut, do it neatly such thatthe cut and the un-cut portions are distinguishable. Thinking and formatting the answer beforewriting will improve you on this front. Never leave any question. Write something of what youknow of the answer.
Remember “What you think is wrong may be the correct answer” many a times.
(74)
List of some Super hit topics:
1. CE Transistor amplifier and Oscillator
2. A.C.Generator
3. Transformer
4. Cyclotron
5. Potentiometer
6. Wheatstone's Bridge
7. Young's Experiment
8. Components of Earth's field
9. Application of E.M.Waves
10. Moving coil Galvanometer
11. Photo-electric effect
12. Bohr's Model
13. Modulation and Demodulation with need, advantages and disadvantages with relevant circuits
14. Brewster's Law and Condition for I dark in Diffraction pattern
15. Gauss's theorem - proof and major application on Spherical and line of charges
(75)
CHAPTER- 6
CHALLENGES IN LEARNING
PHYSICS CONCEPTS AND PEDAGOGICAL TIPS
Great men have said that all minds are packed with similar contents. But they work differently based on
the way one tries to use. A systematic approach places everyone on a better platform in academics with
the explosion of knowledge. Learning Obstacles do appear in every learning situation- Major
contribution is from sciences - in particular physics. Even though it is relative --Challenges do exist. With
experience in teaching, one could identify some of the areas in physics where student have a fear or
psychological discomfort.
Some of the identified challenges are listed below :
1. Concept of Gauss's Theorem.
2. Force on a Charge in a Magnetic field
3. Finding the direction of Induced current
4. Study ofAmplifiers in CE- Configuration
To find electric field using Gauss Theorem.
(i) Unable to construct a Gaussian surface
(ii) Finding effective Gaussian area
(iii) Checking for charge enclosed.
(i) Gaussian surface is always symmetrical.
(ii) Even if unsymmetrical is made, the area where the field is perpendicular to the
surface has to be accounted for.
(iii) If only field lines pass through the surface and no charge is enclosed the net flux has
to be zero.
(iv) Flux being a scalar, the net flux is the sum of flux due to all the surfaces involved.
1. Concept of Gauss's Theorem:-
Aim :
Problem :
Solution : As per the course XII requirement,
(76)
2.
Aim :
Problem :
Solution :
3.
Problem :
Force on a charge in a magnetic field.
Identifying the direction of Induced current
Identifying force direction
(i) Sense of directional representation
(ii) Unable to identify the differences due to the nature of charges.
(i) During conceptualization, one should understand that the rules are always framed for
the positive charge motion.
(ii) Fleming's rule is used only when the field and the motion are perpendicular to each
other.
(iii) It may be practiced that one can better turn the note book rather than the hand to arrive
at result i.e. force direction.
Unable to identify the direction of induced current
Solution :
if
then
4.
Problem :
Solution :
(i) Express the Fleming's Right hand rule the way it has to be. Students generally associate
the three fingers with the three quantities Magnetic field, Motion of conductor and the
Induced current direction. It should be noted that the fore finger indicates the magnetic
field and the thumb indicates the direction of the motion of the conductor the
middle finger points the direction of Induced current.
(ii) Recall that the rule is applicable for only perpendicular direction of the Magnetic Field
and motion of the conductor.
(iii) Recall that there needs to be a closed path available for the current to flow. If the closed
path exists completely inside the magnetic field, there may be no current but emf may be
produced.
(iv) It must again and again impress upon that there may be constant field or flux but for
induced emf the field or flux has to change.
Unable to draw a circuit diagram and explain the process of Amplification.
(i) Draw the Transistor with indication of npn or pnp.
(ii) Give Bias for the input and Output side Emitter should be forward biased and
Collector has to be reverse biased.
Study ofAmplifiers in Common- Emitter Configuration
(77)
(iii) Recall that to keep forward bias in the emitter, the signal for amplification has to have amplitude
less than the bias potential.
(iv) Show all these three in the circuit and indicate the direction of current and establish the
conservation of current.
(a) No signal exists
(b) Forward cycle is fed in and
(c) Reverse cycle is applied as input along with the bias potential.
(v ) Try to appreciate the fact that the output with zero signal when adds to addition of forward/
reverse cycle signal there will be increased amplitude.
(vii) Recall as Forward bias increases, increases causing V to decrease and vice-versa causing a
180 phase difference between the output and input.
Like these analysis, the teacher may think, prepare some tips and try to simplify the topics without losing
technicality. Teacher preparedness is tested by every child, when a brilliant question is posed in the class
room. A patient listening to the problems of the child, at least five minutes of mind set for each session
and a goal set for the year, may keep the teacher at better level and the taught will overcome the word
“Challenge and Hard” with positive outlook. Teacher is expected to approach every area conceptually
and device simple steps for the child to follow rather than arriving at the answers to the questions. This
will bring a totally refined approach to teaching learning process and no doubt ignited minds will be
grown in our class-rooms.
I = I + I
I
e c b
c
(v) Write the Kirchoff's rule for the output side V = V - I R and try to explain what happens when
i
ce cc c c
cc
o
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CHAPTER-7
TIPS TO SOLVE NUMERICAL QUESTIONS
Out of all the most ways by which a taught is tested by a teacher the most dreaded is with Numerical
Problems in physics. Due to some teachers, the taught is in the impression that numerical solving alone
can take him to good heights in academics. The fact remains hidden that CBSE class XII physics paper
will have numerical problems worth only. This is again specified only in the guidelines of
2007 sample papers physics XII. The very argument here is not to avoid them but to strengthen your-self
to do the numerical problems with ease and develop a systematic approach to solve them. Text book
reading habit is somehow lost by the children of Delhi and it should be the prime task for all concerned to
bring this habit to the minds of the pupil. If ample opportunity is given to the mind to conceptualize a
given topic, it will solve any problem under the mastered topic. So a systematic approach is expected to
solve numerical. Before a child begins to solve numerical problems, he / she should have read,
comprehended, conceptualized and be prepared mentally to face the variations in any parameter. Merely
memorizing the formula and trying to substitute the values will not solve the problem and this practice
should be stop and discouraged.
Let us take some examples in solving numerical problems and see how the change in approach removes
the problem faced:
In potentiometer based questions, the following steps lead to clear understanding and correct
results:-
A. Draw the circuit diagram from the information given in the question.
B. In the Primary Circuit
(i) Find the current through potentiometer wire.
(ii) Find potential difference across the potentiometer wire
(iii) Find potential gradient V = V/Lwhere Lis the length of the potentiometer wire.
C. Using the Secondary circuit
(iv) Try to find the balancing for an emf or terminal voltage of the cell in the secondary circuit using
potential gradient (V .) i.e. V . X = V or E
(v) V or E has to be chosen or found based on whether any shunt resistor exists or not.
15 marks
1.
Student should be advised to use the concepts rather than apply the formula.
Potentiometer related questions:-
.
g
g g
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CHAPTER-8
POINTS TO PONDER (NCERT CLASS XII TEXTBOOK)
1.Electric Charges and Fields
2.Electrostatic Potential and Capacitance
Point 6 :
Point 8 :
Point 4 :
Point 7 :
NCERT
Velocity of a body is different in different frames of reference and so does the kinetic energy.
Kinetic energy is also depends on the mass which differs with the velocity of the particle when it
is comparable to the speed of light. Charge is a scalar and is not a frame dependent quantity.
Quantisation of charge as a phenomena is supported with the Millikan's oil drop experiment. So it
can be a law of nature. However, when the existence of the particles like Quark is established
there will be a drop in the scale of quantization to 1/3 of the charge on electron.
Slight deviation of the dipole from the electric field can bring a restoring torque and as a result
there can be a S.H.M. The restoring torque can be 2 l xq E Sin and can be equated to Time
period can be easily found from the relation �The oscillation will be a damped only
when� there is presence of dissipative forces.
A cavity is free from Electric field even if there are charges on the surface of a conductor.
However if there is a charge placed inside the cavity, it will create a field in all its surroundings extending
to infinity. This is established from the approach of spherical symmetry discussed in the text
book. So electrostatic shielding is not possible with a charge inside the cavity.
rd
[- �� � �
2 � I2 l q E
(81)
3.Current Electricity
4. Moving Charges and Magnetism
Point 1 :
Point 6:
Point 1 :
The current flowing in a conductor is given by the integral j. ds So even if a uniform
conductor is considered the current density is taken a constant over a smaller element and the
current can be found. Both the density and area are vectors satisfying the law of vector addition
and only the component of j in line with the area vector or normal to the area contribute to the
current.
The shape of the circuit in any way does not influence the flowing current. The conservation of
charge is obeyed in whatsoever way one bends the loop. Quite often students take into different
values of resistance and thereby current when a wire is bend into a square or a circle and the
equivalent resistance is found between the diagonally opposite ends.
One of the remarkable difference between the electric and the magnetic field is that the magnetic
field lines form closed path and the electric field lines do not. The direction of field between the
poles of a magnet is from the south to North in line with the field while in a electric dipole the field
is from the +ve charge to the -ve charge.
� �
Point 3 :
Point 7 :
The Lorentz force will signify only the electric force if the frame of reference is having a velocity
and in its reference the charge is at rest. The very motion of the charge is to be defined with the
presence of an electric field. This is the second indication for the student to understand that there
exists a link between the electric and magnetic field. [ The first link is in the continuity developed
between the plates of a capacitor due to the changing electric field causing a magnetic effect.]
The phenomena of Hysteresis is a control on human by nature. It is the study of the inability to
retrace the same path while magnetizing and Demagnetizing. In the making of a magnet one does
work and align the dipoles in an order. Similarly demagnetizing is also a orderly disorderliness
expecting man to do work. The Domain theory of Ferromagnetism explains the formation of the
Hysteresis loop. The area covered by the Hysteresis is a measure of the energy used for unit
volume of the material per cycle of magnetization and demagnetization.
5. Magnetism and Matter
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Point 8 :
Point 3 :
Diamagnetism is a universal property. Superconductors expel magnetic field [Meissner Effect] as
do the Diamagnets. So every material is said to exhibit this property at one temperature or
another.
Induced emf is possible when there is a variation in area, field and/or the orientation of the area
with the field. So when there is a moving charge in a fixed field or a varying field in a static charge
there will be induced emf.
6. Electromagnetic Induction
Point 3
Point 7 :
Point 8 :
:
The Lorentz force will signify only the electric force if the frame of reference is having a velocity
and in its reference the charge is at rest. The very motion of the charge is to be defined with the
presence of an electric field. This is the second indication for the student to understand that there
exists a link between the electric and magnetic field. [ The first link is in the continuity developed
between the plates of a capacitor due to the changing electric field causing a magnetic effect.]
The phenomena of Hysteresis is a control on human by nature. It is the study of the inability to
retrace the same path while magnetizing and Demagnetizing. In the making of a magnet one does
work and align the dipoles in an order. Similarly demagnetizing is also a orderly disorderliness
expecting man to do work. The Domain theory of Ferromagnetism explains the formation of the
Hysteresis loop. The area covered by the Hysteresis is a measure of the energy used for unit
volume of the material per cycle of magnetization and demagnetization.
Diamagnetism is a universal property. Superconductors expel magnetic field [Meissner Effect] as
do the Diamagnets. So every material is said to exhibit this property at one temperature or
another.
5. Magnetism and Matter
6. Electromagnetic Induction
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Point 4 :
Point 5 :
Point 9 :
The eddy current formed in the plate creates a magnetic field which is opposed by the applied
magnetic field [ Lenz's explanation ]. So there is a damping effect on the disc made to oscillate in
the presence of a magnetic field.
In an a.c. network having an inductor, a capacitor and a resistor in series the net potential applied
is given by the relation where the symbols carry the usual meaning. This is
because of the phase difference that exists between the voltage and the current. The same reason
holds when current conservation is to be established with a Capacitor and an Inductor in parallel.
The current drawn from a source is given by the relation
The average power consumed by the ac circuit is given by the relation where
is the phase difference between the voltage and the current. Since the value of Cos is to be less
than 1 this value decides the proportion of maximum power that will be consumed in the ac
circuit. It is given by the ratio of the Resistance to the Impedance of the circuit.
7.Alternating Current
V= (V - V ) + V
Similar to what has been explained in this point we can observe as we place a screen
perpendicularly along the axis of a convex lens receiving white light. Since the lens medium
offers different refractive index for different constituent colours the (same) lens offers different
focal length. On the screen one can observe coloured rings with violet at the centre and red at the
extreme - close to the lens and as one moves the screen away there will be a position with red
colour as the centre and violet as the outer ring.
It may added to the point 1 that Huygen was not able explain
(i) Why the energy released by any Wavefront goes only in the forward direction?
(ii) Is light a transverse or a Longitudinal wave?
The spark created by Huygen has made Young, Fresnel and Fraunhofer to explain various
phenomena associated with light. The first question was answered byYoung. The intensity
with �as the phase difference will become zero for the backward direction. The
second question was answered by the Polarization experiment establishing the Transverse nature
of light.
L C R
2 2
9. Ray Optics and Optical Instruments
10. Wave Optics
Point 2 :
Point 1:
P = I V Cos
I=2a ( 1+Cos )
av rms rms �
� �
� � �2
I=I -IC L
(84)
Point 4:
'D' 'a'
Point 4:
Point 5 :
14. Semiconductor Electronics; Materials, Devices and Simple Circuits
The limit of application of Ray optics was established by Fresnel's distance. As the divergence of
the light over a distance exceeds the slit width then wave optics has to be applied. The
distance D with such a spread called Fresnel distance D The angular width for this
distance is a and corresponds to the first minima of the diffraction pattern and also the clear
resolution limit for telescopes.
The shift from particle to wave was challenged by the Photo-electric effect which made mankind
to consider energy as a packet with energy equivalent and indirectly established the dual
nature of matter later supported by the Davisson and Germer experiment.
The dual nature also showed difference between the Classical and Modern Physics in
distinguishing the effects of Intensity variation and Frequency variation.As you may recall that
(i) minimum frequency is required for Photo-electric emission to take plac even though the Intensity
is increased
(ii) the stopping potential is measured with the frequency rather than the Intensity.
� a /
For a transistor to work the way it is expected [as from its name] to work the following points are
to be kept in mind.
(i) The emitter is to be densely doped
(ii) The base region should be lightly doped and thin
(iii) The collector region is to be moderately doped
(i) The emitter should be forward biased
(ii) The Collector is to be reverse biased.
This will make the transistor to perform its task of transferring Majority carriers from low
resistance region [emitter] to the high resistance region [collector].
2
� �
11. Dual Nature of Radiation and Matter
hν
Point 3:
While using a transistor in a circuit
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CHAPTER-9
SUGGESTIONS TO IMPROVE THE COMMON ERRORSCOMMITTED BY STUDENTS IN EXAMS
1. The teachers should tell the students about the possible distribution of marks over the different value
points (or different requirements) specially for a long answer question. For example distribution of 5
marks in a descriptive type question may be distributed over different aspects such as diagram,
labelling, description, derivation, formulas, properties, limitation, precautions, application etc.
whatever may be, depending on the question.
2. If the answer is suported by a diagram, then the following points should be taken the account.
(i) Placement of the diagram
(ii) Proper labelling.
(iii) Appropriate reference of diagram in the answer.
(iv) Specific requirements in the diagram depending on the type of question e.g.
— Path of rays or positions of object/image for question on optics.
— Direction of electric current in electricity questions.
— Location of charge in electrostatic questions.
— Use of graphs depicting the requirement.
3. Regarding numerical question, the students should be conversant with and so should be told the
following points during the class room teaching:
(i) Possible distribution of marks over value points
(ii) Conversion of units of different physical quantities into same system.
(iii) Use of correct formulas with standard notations, stating their usual meaning.
(iv) Use of diagram, if needed for solving numerical.
(v) Correct substitution of values in the formula and calculation of result in proper form.
(vi) Expression of result in proper unit.
4. While defining a physical quantity it should be taken that it can be defined ‘qualitatively’ as well as
quantitively. Student should not confuse between actual definition and its mathematical expression..
For some physical quantities (e.g. magnetic moment), unit of the quantity should correspond to the
definition stated.
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5. All answer should be ‘‘brief and to the point’’. The expected depth of the answers should be to the
extent given in the prescribed text books. Irrelevant or unnecessary long answers involve wastage of
time. Length of the answer is usually related with the marks
The number of words mentioned in the question papers for different types of answers are only
suggestive. If may be difficult to write the answers within this specified number of words sometimes.
Irrespective of the word limit an answer must contain the desired matter. This should be made clear to
students in the class.
6. If a student is unable to understand or ascertian about the requirement of a question it is advisable that
the other version of the question (Hindi/English) may be read. A student has to identify the ‘action
verb’or the key word in the question which specifies the task.
7. It is advisable that students should be fully conversant with the ‘Design’of the question paper and the
different parameters involved in it ( length of answers, objectives, difficulty level, unit wise
marks etc).
Astudy of erformance analysis of students in physics, C. B. S. E. Delhi.
e.g
Source: P
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CHAPTER-10
EDUCATIONAL RESOURCES ON INTERNET
Department of education, Government of India
University Grant Commission
Information and Library Network Centre
Academics-India
National Informatics Centre
Educational Institutions Resource Bank of India
All India Council forTechnical Education
National Council ForTeacher Education
National Council of Educational Research and Training
Zeelearn-The Complete Learning Portal
Schools ahead
Entrance Booster
http://www.education.nic.in
http://www.ugc.ac.in
http://www.inflibnet.ac.in
www.academics-india.com
http://www.nic.in
http://www.indiaedu.com
http://www.aicte.com
http://www.ncte-in.org
http://www.ncert.nic.in
http://www.zeelearn.com
http://www.schoolsahead.com
http://www.entrancebusters.com
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PHYSICS RESOURCES ON INTERNET
http://www.phys.washington.edu/groups/peg/index.html
http://www.howstuffworks.com/
http://www.tryscience.org
http://www.physics.org/
http://www.physicsgre.com/
http://www.smartkidssoftware.com/ndpir1.htm
http://www.bcspanthers.org/physicswebsites.htm
http://www.learner.org/exhibits/parkphysics/resources.html
http://www.phy.bris.ac.uk/groups/particle/PUS/Teachers.html
http://www.teachingideas.co.uk/science/contents.htm
http://www.teach-nology.com/ teachers/subject_matter/science/physics/
http://shs.westport.k12.ct.us/mjvl/science/physicsweb.htm
http://serendip.brynmawr.edu/sci_edu/
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