MODEL SCHOOL @ G.ARIYUR THIRUKOVILUR, VILLUPURAM (DT)-605751.

PHYSICS

XII-STANDARD

STUDY MATERIAL (FOR SLOW LEARNERS)

PREPARED BY:

V.MANIKANDAN.M.Sc.,B.Ed.,

PG ASSISTANT IN PHYSICS,

MODEL SCHOOL @ G.ARIYUR,

THIRUKOVILUR,

VILLUPURAM (DT)-605751.

CELL: 9843431804.

“Failure will never overtake me if my determination to succeed

is strong enough” -ABDUL KALAM

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+2 PHYSICS

3 MARK STUDY MATERIAL

(for slow learners)

Prepared by:

V.MANIKANDAN.M.SC.,B.Ed.,

PG ASST. IN PHYSICS,

MODEL SCHOOL @ G.ARIYUR,

THIRUKOVILUR,

VILLUPURAM-605751

CELL:9843431804

www.kalvikural.com

1. Electrostatics 1.Coulomb’s law : The force is directly proportional to the product of the charges and inversely proportional to the

square of the distance between them. F αααα ����

��

2.Properties of lines of forces: (i) It start from positive charge and to negative charge. (ii) It never intersect. (iii) The tangent to a line of force at any point gives the direction of the electric field (E) at that point. 3.Electric dipole Two equal and opposite charges separated by a very small distance constitute an electric dipole. ex : water 4. Electric potential The amount of work done in moving a unit positive charge from infinity to that point against the electric forces. 5.Electric flux The total number of electric lines of force, crossing through the given area. 6.Gauss’s law The total flux is equal to 1/εo times the net charge enclosed by the surface. 7.Applications of capacitors. (i) They are used in the ignition system (ii) They are used to reduce voltage fluctuations. (iii) Capacitors are used in tuning the radio circuit. 8.Action of points or corona discharge. The leakage of electric charges from the sharp points on the charged conductor. 9.Why it is safer to sit inside a bus or car than in open ground or under a tree? The metal body of the bus/car provides electrostatic shielding, where the electric field is zero. The electric discharge passes through the body of the bus/car.

2. Current Electricity

10.Drift velocity The velocity with which free electrons get drifted towards the positive terminal, when an electric field is applied. Unit : m/s 11.Mobility

The drift velocity acquired per unit electric field. Unit : �� ��� 12.Ohm’s law The steady current flowing through a conductor is directly proportional to the potential difference.

I αααα V

13.Applications of superconductors (i) It form the basis of energy saving power systems. (ii) Superconducting magnets have been used to levitate trains above its rails. (iii)It can be used to separate tumor cells from healthy cells. (iv) It can be used for transmissionlines. (v) It can be used as memory elements.

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14.The temperature coefficient ofresistance The ratio of increase in resistance per degree rise in temperature to its resistance at �� C. Unit : /�C. 15.Comparison of emf and potential difference

S.NO Emf potential difference

1. 2. 3.

It measured in open circuit (Daniel cell) It is independent of resistance. Unit : Volt

It measured in closed circuit (potentiometer) Here V αααα R Unit : Volt

16. The changes observed at the transition temperature:

(i) The electrical resistivity drops to zero. (ii) The conductivity becomes infinity (iii) The magnetic flux lines are excluded from the material. 17.Kirchoff’s first law The algebraic sum of the currents meeting at any junction in a circuit is zero. 18.Electric energy and electric power.

S.NO Electric energy Electric power

1. 2. 3.

The rate of doing electric work P=VI Unit : watt

The capacity to do work Energy = VIt Unit : watt hour

19.Faraday’s laws of electrolysis First Law : The mass of a substance is proportional to the charge passing through the electrolyte.

m α q Second Law : The mass of a substance is proportional to the chemical equivalent of the substance.

m α E 20.Primary Cell and secondaery cell

S.NO Primary Cell Secondaery cell 1. 2. 3

Irreversible chemical actions It cannot be recharged Ex : Daniel cell

Reversible chemical actions It can be recharged Ex : Lead-acid accumulator (used in all automobiles)

21. The resistance of a nichrome wire at 0o C is 10 ΩΩΩΩ. . . . If its temperature coefficient of resistance is 0.004/oC, find its resistance at boiling point of water. Comment on the result.

Rt = Ro (1+ α t) Rt = 14 Ω

As temperature increases the resistance also increases.

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3. Effects of electric current

22.Why nichrome is used as the heating element (1) It has high specific resistance (2) It has high melting point (3) It is not easily oxidized 23.Limitations of Cyclotron (i) Maintaining a uniform magnetic field over a large area of the Dees is difficult. (ii) The electrons cannot be accelerated. (iii) At high velocities, relativistic variation of mass of the particle upsets the resonance condition.

4. Electromagnetic Induction and Alternating Current 24.Methods of producing induced emf By changing (i) the magnetic induction (B)

(ii) area enclosed by the coil (A) and (iii) the orientation of the coil (θ) with respect to the magnetic field.

25.Fleming’s right hand rule or generator rule The forefinger, the middle finger and the thumb of the right hand

are held in the three mutually perpendicular directions. If the forefinger points magnetic field the thumb motion of the conductor, then the middle finger induced current. 26.Faraday’s laws of electromagnetic induction

First law [what is electromagnetic induction?] Whenever the amount of magnetic flux linked with a closed circuit changes, an emf is induced in the circuit.

Second law Emf induced is directly proportional to the rate of change of magnetic flux.

e αααα��

��

27.Lenz’s law The induced current produced in a circuit always flows in such a direction that it opposes the change or cause that

produces it. e = –N��

��

28.Q-factor The ratio of the voltage across a coil to the applied voltage. 29.Distinguish b/w AF Choke coil and RF Choke coil

S.NO AF Choke coil RF Choke coil

1. 2. 3.

Frequency is low Inductance is high. Iron core is used

Frequency is high Inductance is low No Iron core is used

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30. An aircraft having a wingspan of 20.48 m flies due north at a speed of 40 ms−−−−1. If the vertical component of earth’s magnetic field at the place is 2 × 10−−−−5 T, Calculate the emf induced between the ends of the wings.

e = − B l v e = − 0.0164 V 5. Electromagnetic Waves and Wave optics

31.Tyndal scattering When light passes through a colloidal solution its path is visible inside the solution. The scattering of light by the colloidal particle is called Tyndal scattering. 32.Why the sky to appear blue? According to Rayleigh’s scattering law, blue light is scattered to a greater extent than red light. This scattered radiation causes the sky to appear blue. 33.On what factors depends optical rotation? (i) thickness of crystal (ii) density of the crystal or concentration in the case of solutions. (iii) wavelength of light used (iv) the temperature of the solutions. 33. Uses of IR (infrared ) rays (i) Infrared lamps are used in physiotherapy. (ii) Infrared photographs are used in weather forecasting. (iii)Infra red absorption spectrum is used to study the molecular structure. 34.Differences b/w Fresnel and Fraunhofer diffraction 35. A plano – convex lens of radius 3 m is placed on an optically flat glass plate and is illuminated by monochromatic light. The radius of the 8th dark ring is 3.6 mm. Calculate the wavelength of light used. ��

� =nRλ

λ =5400 Å 36. In Newton’s rings experiment the diameter of certain order of dark ring is measured to be double that of second ring. What is the order of the ring? ��

� = 4nRλ

n = 8.

S.NO Fresnel diffraction Fraunhofer diffraction

1. 2. 3.

wave front is spherical or cylindrical. Rays are unparallel to each other No convex lens is used

wavefront is plane. Rays are parallel to each other. Convex lens is used

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6. Atomic Physics 37.Moseley’s law The frequency of the characteristic X-ray spectrum is proportional to the square of the atomic number (Z) of the element considered. ν α ��

38.Characteristics of laser (i) is monochromatic (ii) is coherent (iii) does not diverge at all (iv) is highly intense

39.Conditions to achieve laser action (i) There must be an inverted population (ii) The excited state must be a metastable state. (iii) The emitted photons must stimulate further emission. 40.Laue two important facts (i) X–rays are electro magnetic waves of very short wave length. (ii) The atoms in a crystal are arranged in a regular 3D lattice. 41.Calculate the longest wavelength that can be analysed by a rock salt crystal of spacing d = 2.82Å in the first order. 2d sin θθθθ = nλλλλ λλλλ = 5.64 ��

7. Dual Nature of Radiation and Matter and Relativity

42.Postulates of the special theory of relativity (i) The laws of Physics are the same in all inertial frames of reference. (ii) The velocity of light in free space is a constant in all the frames of reference. 43.Uses of electron microscope (i) to study the structure of textile fibres. (ii) to study virus and bacteria. (iii) to study atomic structure . 44.Limitations of electron microscope (i) It is operated only in high vacuum. (ii) It is not applicable to study the evaporate and disintegrate of living organisms. 45. Cut-off or stopping potential. The minimum negative potential given to the anode for which the photo electric current becomes zero. 46.Uses of photo electric cells (i) It is used for automatic switching on and off the street lights. (ii) It is used in opening and closing of door automatically. (iii) It is used in burglar alarm and fire alarm. (iv) It is used for reproducing sound in cinematography.

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8. Nuclear Physics 47.Properties of neutrons (i) Neutron present in all nuclei, except hydrogen. (ii) They are not deflected by electric and magnetic fields. (iii) Neutrons are stable inside the nucleus. But outside the nucleus they are unstable. (iv) They penetrate any nucleus. (v) Neutrons are classified to slow neutrons and fast neutrons. 48.Define-Roentgen The quantity of radiation which produces 1.6 × 10� pairs of ions in 1 gram of air. 49.Define-Curie The quantity of a radioactive substance which gives 3.7 × 10� becquerel. 50.Pair production and annihilation of matter Pair production:The conversion of a photon into an electron−positron pair. Annihilation of matter: A n electron and positron combine to produce a photon.

9. Semiconductor Devices and their Applications

51. Advantages ICs (i) Very small in size (ii) Very small weight (iii) Easy replacement (iv) Reduced cost (v) Reliability 52.Advantages of negative feedback (i) Highly stabilised gain. (ii) Reduction in the noise level. (iii) Increased bandwidth (iv) Increased input impedance and decreased output impedance. (v) Less distortion. 53.Barkhausen condition for oscillation (i) The loop gain Aββββ = 1 (ii) The net phase shift is 0� or integral multiples of 2π. 54.Universal gates Universal gates: NAND and NOR gates Because: They can perform all the three basic logic functions. 55.Bandwidth The frequency interval between lower cut off and upper cut off frequencies.

BW = fU – Fl 56.De-Morgan’s theorems First theorem “The complement of a sum is equal to the product of the complements.”

A++++B = A .B Second theorem “The complement of a product is equal to the sum of the complements.”

A . B = A++++B.

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57.Rectification and Rectifier Rectification : The process of converting from a.c to d.c. Rectifier: The device used for this process is called as rectifier. Ex: diode 58.Uses of CRO (Cathode Ray Oscilloscope) (i) It is used to measure a.c and d.c voltage. (ii) It is used to study the waveforms of a.c voltages. (iii) It is used to find the frequency of a.c voltage. (iv) It is used to study the beating of heart in cardiology. 59.NPN Transister-CE mode:

10. Communication Systems

60.Skip distance For a fixed frequency, the shortest distance between the point of transmission and the point of reception along the surface 61.Modulation factor The ratio of Signal amplitude to the Carrier amplitude.

m = ����� �!" �#$%&

'����&��!" �#$%&

Prepared by:

V.MANIKANDAN.M.SC.,B.Ed.,

PG ASST. IN PHYSICS,

MODEL SCHOOL @ G.ARIYUR,

THIRUKOVILUR,

VILLUPURAM-605751

CELL:9843431804

www.kalvikural.com

V.MANIKANDAN.M.Sc.,B.Ed., PG Asst. in PHYSICS, MODEL SCHOOL,G.ARIYUR,THIRUKOVILUR. Cell: 9843431804

PHYSICS

HIGHER SECONDARY – SECOND YEAR

(FOR SLOW LEARNERS)

5 MARKS

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V.MANIKANDAN.M.Sc.,B.Ed., PG Asst. in PHYSICS, MODEL SCHOOL,G.ARIYUR,THIRUKOVILUR. Cell: 9843431804

5 MARKS

1.Properties of lines of forces:

(i) It starts from positive charge and ends at negative charge. (ii) It never intersect. (iii) The tangent to a line of force gives the direction of E. (iv) E is large if they are close together and E is small if they are far part.

(v) Each unit positive charge gives 1/εo lines of force in free space. � =�

��

2.Applications of superconductors (i) It is used as a superconducting generators (ii) Superconducting magnets is used to levitate trains above its rails. (iii) Superconducting magnetic propulsion system is used to launch satellites. (iv) It can be used for transmission lines. (v)It can be used as memory elements in computers. 3.Features of Magnetic lorentz force: The force (i) on the charge is zero, if the charge is at rest. (ii) is proportional to the charge (q) (iii) is proportional to the magnetic induction (B) (iv) is proportional to the speed of the charge (v) (v)is maximun when charge move perpenticular to the field. 4.Characteristics of electromagnetic waves (i) They are produced by accelerated charges. (ii) They do not require any material medium for propagation. (iii)They are transverse in nature. (iv) They travel in vacuum with a velocity “c” (v) They are not deflectedby electric and magnetic fields. 5.Uses of Polaroid 1. They are used to produce and analyse plane polarised light. 2.They are used as polarising sun glasses. 3. They are used to eliminate the head light glare in motor cars. 4. They are used to improve colour contrasts in old oil paintings. 5. Polaroid films are used to produce 3D moving pictures. 6.Properties of Cathode / canal / alpha / beta / gamma/ X - rays

(i) They travel in straight lines. (ii) They affect photographic plates. (iii) They can produce fluorescence. (iv)They ionize the gas through which they pass. (v) They produce heat, when they fall on matter. 7.Applications of photo electric cells (i) They are used for reproducing sound incinematography. (ii) They are used for controlling the temperature offurnaces. (iii)They are used for automatic switching onand off the street lights. (iv) They are used in opening and closing of doorautomatically. (v) They are used in burglar alarm and fire alarm.

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V.MANIKANDAN.M.Sc.,B.Ed., PG Asst. in PHYSICS, MODEL SCHOOL,G.ARIYUR,THIRUKOVILUR. Cell: 9843431804

8.de Broglie’s wavelength of matter waves E = hν

E = m�� hν = m��

λ =�

if c = v

λ =�

�

λ =�

�

p = mv 9. Electron microscope Uses: (i) It is used to study the structure of textile fibres, surface of metals. (ii) It is used to study the virus andbacteria. (iii) It is used to study the atomicstructure and of crystal structure. Limitations:

(i)It is operated only in high vacuum. (ii)It cannot used to study living organisms which would evaporate.

10. Properties of neutrons

(i) Neutrons are the constituent particles of all nuclei, excepthydrogen. (ii)They are not deflected byelectric and magnetic fields. (iii) Neutrons are stable inside the nucleus. But outside the nucleus they are unstable with half life of 13 minutes. (iv)They can easily penetrate anynucleus. (v) Neutrons are classified to (a) slow neutrons and (b) fast neutrons. 11.De-Morgan’s theorems First theorem “The complement of a sum is equal to the product of thecomplements.”

Second theorem “The complement of a product is equal to the sum of thecomplements.”

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12.Energy losses in a transformer(1) Hysteresis loss

This is due to repeated magnetisation and demagnetisation of the iron core. This loss can be minimised by using mumetal andsilicon steel(2) Copper loss This is due to loss of heat energy in minimised by using thick wires with (3) Eddy current loss (Iron loss)This is due to loss of heat energy in corecore made of stelloy, an alloy of steel. (4) Flux loss

This loss is due to fluxleakageshell type core. (5)Due to the vibration of the core,sound is produced, which causes a loss in the energy. 13. Brewster’s law

The tangent of the polarising angle is numerically equal to therefractive index of the medium.14.Self inductance of a long solenoid

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12.Energy losses in a transformer

magnetisation and demagnetisation of the iron core. This loss can be minimised by using mumetal andsilicon steel.

is is due to loss of heat energy in the primary and secondary windingshick wires with considerably low resistance.

(3) Eddy current loss (Iron loss) is is due to loss of heat energy in core. This loss isminimised by using a laminated

core made of stelloy, an alloy of steel.

leakage in secondary coil. This loss can be minimised by using a

ue to the vibration of the core,sound is produced, which causes a loss in the energy.

The tangent of the polarising angle is numerically equal to the index of the medium.

Self inductance of a long solenoid

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magnetisation and demagnetisation of the iron core. This loss

the primary and secondary windings.It can be

. This loss isminimised by using a laminated

This loss can be minimised by using a

ue to the vibration of the core,sound is produced, which causes a loss in the energy.

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15.Emf induced by changing the area enclosed by the coil PQRS is a conductor bent in the shape. A uniform magnetic field ‘B’ acts perpendicular to the plane of the conductor.

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Emf induced by changing the area enclosed by the coil

PQRS is a conductor bent in the shape. A uniform magnetic field ‘B’ acts perpendicular

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PQRS is a conductor bent in the shape. A uniform magnetic field ‘B’ acts perpendicular

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V.MANIKANDAN.M.Sc.,B.Ed., PG Asst. in PHYSICS, MODEL SCHOOL,G.ARIYUR,THIRUKOVILUR. Cell: 9843431804

16.Wheatstone’s bridge

If Ig=0

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17.Thermopile Thermopile is a device used to detect thermal radiation. It works onthe principle of Seebeck effect.

• a single thermocouple gives a very small emf, a large numberof thermocouples are connected in series.

• The other set ofjunctions (2,4) called cold junction is shielded from the radiation.

• When thermal radiation falls on (1, 3, 5)

• The deflection in the galvanometer isproportional

18.

s.no

series

Electron jufrom higher

orbit(lower

�

1. 2. 3. 4. 5.

1 2 3 4 5

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Thermopile is a device used to detect thermal radiation. It works on

a single thermocouple gives a very small emf, a large number

thermocouples are connected in series.

The other set ofjunctions (2,4) called cold junction is shielded from the radiation.

When thermal radiation falls on (1, 3, 5), a largethermo emf is produced.

The deflection in the galvanometer isproportional to the intensity of radiation.

Electron jumps from higher

rbit( �) to lower( �)

wavenumber Present region

�

2,3,4,…

3,4,5,…

4,5,6,…

5,6,7,…

6,7,8,…

Visible

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Thermopile is a device used to detect thermal radiation. It works on

a single thermocouple gives a very small emf, a large number

The other set ofjunctions (2,4) called cold junction is shielded from the radiation.

largethermo emf is produced.

to the intensity of radiation.

Present region

UV Visible IR IR IR

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V.MANIKANDAN.M.Sc.,B.Ed., PG Asst. in PHYSICS, MODEL SCHOOL,G.ARIYUR,THIRUKOVILUR. Cell: 9843431804

19. Bragg’s law for X-ray diffraction

*Consider homogeneous X–rays of wave length angle θ *Let the crystal lattice spacing between the planes be *The path difference between the two waves is equal to

20.Length contraction or Lorentz

This is known as Lorentz – Fitzgerald contraction.Example : A circular object will appear as an ellipse for a fast moving observer.

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ray diffraction

rays of wave length λincident on a crystal at a glancing

*Let the crystal lattice spacing between the planes be d. *The path difference between the two waves is equal to PE + EQ.

20.Length contraction or Lorentz-Fitgerald contraction

Fitzgerald contraction. Example : A circular object will appear as an ellipse

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incident on a crystal at a glancing

motion.

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21.Time dilation Consider two frames S and S′. Let Swith respect to S in the positive X–direction Then theinterval t recorded by him is

22.Satellite Communication: Merits and DemeritsMerits: (i) Mobile communication can be easily established by satellitecommunication.(ii) Satellite communication is economical compared where long distances areinvolved.(iii)The quality of transmitted signaland location of sending and receiving stations are independent ofdistance. (iv) For thin traffic remote areas, it is (v) For search, rescue and navigation, it Demerits: (i) The time delay between talks reduces the efficiency of satellite in datatransmission.(ii) Echo suppressor has to be used to omit echo(iii) Repair of satellite is almost impossible, once it has beenlaunched.

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. Let S′be moving with a velocity v direction.

recorded by him is

Satellite Communication: Merits and Demerits

(i) Mobile communication can be easily established by satellitecommunication. (ii) Satellite communication is economical compared where long distances areinvolved.

quality of transmitted signaland location of sending and receiving stations are independent

raffic remote areas, it is most economical. gation, it is very superior and economical.

reduces the efficiency of satellite in datatransmission.to omit echo.

(iii) Repair of satellite is almost impossible, once it has beenlaunched.

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(ii) Satellite communication is economical compared where long distances areinvolved. quality of transmitted signaland location of sending and receiving stations are independent

reduces the efficiency of satellite in datatransmission.

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23. Capacitors in series and parallel & Resistors in series and parallel:Capacitors in series Capacitors in

parallel

The reciprocal of the effective capacitance is equal to the sum of reciprocal of the capacitance of the individual capacitors.

The effective capacitance of the capacitors connected in parallel is the sum of the capacitances of the ndividualcapacitors

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23. Capacitors in series and parallel & Resistors in series and parallel: Capacitors in Resistors in series Resistors in

The effective capacitance of the capacitors connected in parallel is

capacitances of the ndividualcapacitors

The equivalent resistance of a number of resistors in series connection is equal to the sum of the resistance of individual resistors

The sum of the reciprocal of the resistance of the individual resistors isequal to the reciprocal of the effective resistance of the combination.

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Resistors in parallel

The sum of the reciprocal of the resistance of the individual resistors is equal to the reciprocal of the effective resistance of the combination.

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PHYSICS HIGHER SECONDARY – SECOND YEAR

(FOR SLOW LEARNERS)

10 MARKS

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10 MARKS

1.Electric field due to an electric dipole at a point on 2. Electric field due to an electric dipole at a point on the equatorial line. Its axial line.

3. Electric potential at a point due to an electric dipole 4. Capacitance of a parallel plate capacitor with a dielectric medium.

,

i) ,

ii) ,

iii)

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5. Capacitors in series and parallel

7.Heating effect : Joule’s law

H=VIt Heat produced is directly proportional to i)the square of the current (ii) resistance (iii) time

Capacitors in series Capacitors in parallel

The reciprocal of the effective capacitance is equal to the sum of reciprocal of the capacitance of the individual capacitors.

The effective capacitance of the capacitors connected in parallel is the sum of the capacitances of the ndividualcapacitors

6. Van de Graaff Generator

It can produce large potential difference of

Principle: i) Electrostatic induction ii) Action of points.

Construction: A- hollow metallic sphere B, C- two pulleys D,E- comb-shaped conductors The pulley C is driven continuously by an electric motor. The comb D is maintained at a positive potential of the order of

Working: Action of points- the negative charges in air move towards

the needles and positive charges are repelled on towards the belt.Electrostatic induction- E acquiresacquires positive charge. The acquired positive charge is distributed on the outer surface of the sphere.

The leakage of charge from the sphere can be reduced by enclosing it in a gas filled steel chamber at a very high pressure. Use: accelerate positive ions (protons, deu

8.Emf induced by changing the orientation of the coil (i) Law of current:

PQRS is a rectangular coil of N turns and area A

The coil is rotated clockwise direction . (ii) Law of resistance:

(iii) Law of time:

Capacitors in

The effective capacitance of the capacitors connected in parallel is

capacitances of the ndividualcapacitors

S.NO Alignment of plane with

1. 2. 3. 4. 5.

0

perpendicular parallel perpendicular parallel perpendicular

It can produce large potential difference of

The pulley C is driven continuously by an electric motor. The comb D is maintained at a positive potential of the order of

the negative charges in air move towards the needles and positive charges are repelled on towards the belt.

E acquires negative charge and the sphere charge. The acquired positive charge is

distributed on the outer surface of the sphere. The leakage of charge from the sphere can be reduced by

enclosing it in a gas filled steel chamber at a very high pressure.

accelerate positive ions (protons, deuterons)

8.Emf induced by changing the orientation of the coil

coil of N turns and area A

The coil is rotated clockwise direction .

Alignment of plane with B is

Emf

perpendicular

parallel

perpendicular

parallel

perpendicular

0 0 0

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9.AC generator (Dynamo) – Single phase: 10. Resistor, inductor and capacitor in series: It is a used for converting mechanical energy into electrical energy. Principle: Electromagnetic induction Essential parts of an AC generator: (i) Armature: It is a rectangular coil.

The copper wire wound on laminated soft iron core . (ii) Field magnets: For high power dynamos, field is given by electro magnet. Armature rotates between the magnetic poles. (iii) Slip rings: Two hollow metallic rings R1 and R2. These rings are fixed to a shaft. (iv) Brushes: B1 and B2 are two carbon brushes. They are used to pass the current on external power line. Working: * The induced current direction is given by Fleming’s right hand rule. *ABCD is rotated in the anticlockwise direction. Instantaneous current i = * AB side of the coil moves downwards and DC side moves upwards. The current induced from B to A and fromD to C. 11. Transformer: The current direction – DCBA. Use: Converting low alternating voltage into In external circuit cureent flows from B1 to B2. high alternating voltage and vice versa. *On further rotation, Principle: Electromagnetic induction DC side of the coil moves downwards and AB side moves upwards. Construction: The current induced from A to B and fro C to D. NP - the number of turns in the primary coil

The current direction – ABCD. NS -the number of turns in secondary coil, wound on a soft iron core

In external circuit cureent flows from B2 to B1. EP - induced emf in the primary coil e= Eo sin ωωωωt , ES - induced emf in the secondary coil Eo = NBAωωωω Ip - current in the primary coil N - Number of turns , Is - current in the secondary coil A -Area, B -Magnetic field ωωωω-Angular velocity

:

The efficiency of transformer is always less than one.

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12. Raman effect : 13.Expression for bandwidth The scattered light contains some additional frequencies other than that of incident frequency. Stoke’s lines:The frequency lower than the incident frequency. Anti −−−−stokes lines: The frequencies higher than the incident frequency. Rayleigh line: The spectral line will have unmodified frequency * * * * ΔνΔνΔνΔν is positive and for Anti–stoke’s lines ΔνΔνΔνΔν is negative. *The intensity of Stoke’s line is greater than Anti−stoke’s Line.

The distance between any two consecutive bright or dark bands

14.Determination of specific charge (e/m) of an electron – 15.Bohr atom model: Thomson’s method. Postulates: i)Bohr’s quantization condition: Specific charge: Charge per unit mass of the particle.

ii)Bohr’s frequency condition: Principle:

The cathode rays are deflected byelectric and magnetic fields. electrostatic force

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16.Ruby laser: 17.Helium – neon laser:

*The 5500 Å radiation photons are absorbed by *He – Ne laser containing helium and neon gas in the ratio of the chromium ions 1 : 4 at a total pressure of about 1 mm of Hg. * The excited ion gives up part of its energy to the crystal lattice. *The excited helium atoms transfer their energy to unexcited Ne atoms by collision * E2 has a much longer lifetime * It emits a 6328 Å photon in the visible region. * The population inversion is achieved between * He atom help in achieving a population inversion in Ne atoms. the states E2 and E1.

* It emits a photon of wavelength 6943 Å

18. Bainbridge mass spectrometer – Determination of 19. Geiger – Muller counter Isotopic masses of nuclei:

Use: to measure the intensity of the radioactive radiation. Principle: When nuclear radiations pass through gas,ionisation is produced.

* It is used for the accurate determination of atomic masses. Construction:

*It consists of a metal tube with glass envelope as cathode. * S1 and S2- two slits. and a fine tungsten wire acts as anode.

P1 and P2- two plates to apply electric field. *The tube is filled with an inert gas like argon at a low pressure. *A high potential difference is 1000 V and high resistance

B and B′′′′ – Uniform magnetic fields. is100 mega ohm. * The electric field and magnetic field are nullified one Operation:

by the other *When an ionising radiation enters the counter, primary ionisation takes place and a few ions are produced.

*An avalanche of electrons is produced in a short interval of time. This avalanche of electrons on reaching the anode generates a current pulse

*The counts in the counter is directly proportional to the intensity of the ionising radiation. *The ionisation of the gas is independent of the type of the

The diameter 2R from which radius R can be calculated. incident radiation q- charge m – mass of ion. *G.M. counter does not distinguish the typeof radiation that

enters the chamber.

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20.Nuclear reactor: 21.Cosmic Rays: Principle: Controlled nuclear fission reaction. *The ionising radiation many times stronger than γ-rays entering

the earth from all the directions from cosmic space. Types: i) research reactors, *It can be classified into primary and secondary cosmic rays ii)production reactors * The primary cosmic rays consist of 90% protons, 9%

helium nuclei and remaining heavy nuclei iii) power reactors. Latitude effect:

*The variation of cosmic ray intensity with geomagnetic latitude is known as latitude effect

(1) fuel *The intensity is maximum at the poles (θ = 900), minimum at the equator (θ = 0) and constant between latitudes of

*Nuclear fuel generally used is *The fissile isotopes *In kamini reactor fuel is

(2) Moderator: *It is used to slow down the fast neutrons. *2 MeV of neutron energy reduced to 0.025 eV, Ex: Ordinary water , heavy water &Graphite. (3) Control rods: *The control rods are used to control the chain reaction Altitude effect: * boron or cadmium or boron carbide (B4C), a ceramic material as control rod. *The study of variation of cosmic ray intensity (I) with altitude

(h) is known as altitude effect, *The intensity increases with altitude and reaches a maximum at a height of about 20 km.

(4) The cooling system: *Above this height there is a fall in intensity *It removes the heat generated in the reactor core. Ex: Ordinary water, heavy water and liquid sodium (5) Shielding: As a protection against the harmful radiations, the reactor is surrounded by a concrete wall of thickness about 2 to 2.5 m.

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