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SCIENCE AND TECHNOLOGY I OMTEX CLASSES S.S.C

Achieve Success Through OMTEX CLASSES The Home of Text 1

OMTEX CLASSES

SCIENCE AND

TECHNOLOGYPART ONE

NAME : - ______________________________

STANDARD : - S.S.C

CLASSES : - OMTEX CLASSES

FOR PRIVATE CIRCULATION ONLYYou dont know what you can do until you try

IF YOU ARE SATISFIED WITH OUR TEACHING TELL TO OTHERS IF NOT TELL TO US

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SUCCESSFULLYSUCCESSFULLYSUCCESSFULLYSUCCESSFULLY

STEPPING INTO THE 5TH YEARIN ORDER TO

ACHIEVE ONCE AGAIN SUCCESSONCE AGAIN SUCCESSONCE AGAIN SUCCESSONCE AGAIN SUCCESS

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INDEX

LESSON NAME 1. CLASSIFICATION OF ELEMENTS1. CLASSIFICATION OF ELEMENTS1. CLASSIFICATION OF ELEMENTS1. CLASSIFICATION OF ELEMENTS

2. ELECTROLYSIS2. ELECTROLYSIS2. ELECTROLYSIS2. ELECTROLYSIS

3. STRENGTH OF SOLUTIONS3. STRENGTH OF SOLUTIONS3. STRENGTH OF SOLUTIONS3. STRENGTH OF SOLUTIONS

4. CURRENT ELECTRICI4. CURRENT ELECTRICI4. CURRENT ELECTRICI4. CURRENT ELECTRICITY TYTYTY

5. EFFECTS OF ELECTR5. EFFECTS OF ELECTR5. EFFECTS OF ELECTR5. EFFECTS OF ELECTRIC CURRENT IC CURRENTIC CURRENTIC CURRENT

6 . E N E R G Y S O U R C E S6 . E N E R G Y S O U R C E S6 . E N E R G Y S O U R C E S6 . E N E R G Y S O U R C E S

7 . T Y P E S O F E N E R G Y7 . T Y P E S O F E N E R G Y7 . T Y P E S O F E N E R G Y7 . T Y P E S O F E N E R G Y

8 . P O W E R8 . P O W E R8 . P O W E R8 . P O W E R

9. SOUND9. SOUND9. SOUND9. SOUND

10. HEAT10. HEAT10. HEAT10. HEAT

11. LIGHT11. LIGHT11. LIGHT11. LIGHT

12. MODERN PHYSICS12. MODERN PHYSICS12. MODERN PHYSICS12. MODERN PHYSICS

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I GIVE SCIENTIFIC REASONS.1. VALENCY OF ELEMENTS OF 1ST GROUP IS ONE .

1. Position of an element in the periodic table is related to the electronic configuration.2. Elements in a particular group have the same number of valence electrons.3. Number of valence electrons is equal to the group number.4. Thus all the elements of 1 st group have 1 valence electron.5. They lose this 1 valence electron during chemical reaction.6. Hence, valency of elements of 1 st group is one.

2. T HE FAMILY OF NOBLE GASES IS NAMED AS ZERO GROUPS. 1. In the atoms of noble gases, all the electronic shells including the outermost shell are completely filled.2. They have stable electronic configuration with complete duplet (in the case of He) or complete

octet (in the case of Ne, Ars, etc.).3. Therefore, these elements do not lose, gain or share electrons.4. Hence these elements do not take part in chemical reaction and their valency is zero.5. Hence, the family of noble gases is named as a zero group.

3. INERT GASES EXIST IN THE FORM OF FREE ATOM . 1. Electronic configuration of an atom of an element reveals its ability to form a molecule.2. In the atoms of inert gases, all the electronic shells including the outermost shell are

completely filled.3. They have stable electronic configuration with complete duplet (in the case of He) or complete

octet (in the case of Ne, Ar , etc.).4. Therefore, these elements do not lose, gain or share electrons. Hence these elements do not

take part in the chemical reactions.5. Hence, inert gases exist in the form of free atom.

4. VALENCY VARIES GRADUALLY ALONG A PERIOD . 1. In modern periodic table, the elements are arranged in the increasing order of their atomic

numbers( Z )2. Atomic number of an element is directly related to its electronic configuration.3. As we move from left to right along a period the atomic number goes on increasing and

therefore the number of electrons in the valence shell ( valency ) also goes on increasing.4. The first element in a period has one electron in the outermost shell while the last element in a

period has complete duplet or octet.5. Hence, valency varies gradually along a period.

5. MOLECULAR FORMULAE OF CHLORIDES OF SODIUM AND POTASSIUM ARE SIMILAR WHILETHAT OF SODIUM AND MAGNESIUM IS DIFFERENT .1. Sodium ( Na ) and potassium ( K) belong to 1st group of modern periodic table. These elements

have one electron in the valence shell and thereby they are monovalent.2. In a chemical reaction with chlorine(Cl), they lose their 1 valence electron and this electron is

gained by a chlorine atom forming a molecule of a compound such asa. Sodium chloride ( NaCl ) and b. Potassium Chloride ( KCl ).

3. Magnesium belongs to 2nd group of modern periodic table. It has two electrons in the valenceshell and thereby it is divalent.

4. In chemical reaction with chlorine ( Cl ) magnesium ( Mg ) loses its two valence electrons whichare gained by two chlorine atoms forming molecule of a compound magnesium chloride(MgCl 2).

5. Hence, molecular formulae of chlorides of sodium and potassium are similar while those of sodium and magnesium are different.

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6. SOLUTION OF AN ELECTROLYTE CAN CONDUCT ELECTRICITY BETWEEN TWO ELECTRODES . Ch 21. Most of the electrolytes are electrovalent compounds made up of positive ions and negative ions.2. In the aqueous solution, these ions get separated ( dissociation ) from each other and move freely.3. When an electric potential is applied across the electrodes in contact with the electrolyte the

positively charged ions ( cations ) move towards the cathode and negatively charged ions(anions ) move towards the anode.

4. These movements of cations and anions of an electrolyte are responsible for conductionelectricity through the electrolyte. Hence solution of electrolyte can conduct electricity between twoelectrodes.

7. COPPER IS FOUND TO GET DEPOSITED AT THE CATHODE WHEN CURRENT IS PASSED THROUGHAQUEOUS COPPER CHLORIDE .1. Decomposition of an electrolyte by passage of electric current through it, is called electrolysis.2. During electrolysis of aqueous copper chloride the positively charged copper ions (Cu 2+) move

towards the cathode and accept electrons from the cathode to form copper atoms.3. This can be represented by cathode reaction

4. These copper atoms get deposited on cathode turning it reddish in colour. Hence, copper is foundto get deposited at the cathode when current is passed through aqueous copper chloride.

8. DURING THE ELECTROLYSIS OF AQUEOUS COPPER CHLORIDE USING CARBON ELECTRODES THECOLOUR OF THE ELECTROLYTE GETS FADED .1. Decomposition of an electrolyte by passage of electric current through it is called electrolysis.2. During electrolysis of aqueous copper chloride the positively charged copper ions (Cu 2+) move

towards the cathode and accept electrons from cathode to form copper atoms.3. This can be represented by cathode reaction

4. These copper atoms get deposited on cathode turning it reddish in colour thus the concentrationof the solution goes on decreasing, fading the blue colour of the solution.

5. Hence, during the electrolysis of aqueous copper chloride using carbon electrodes the colour of the electrolyte gets faded.

9. WHEN A BRASS ARTICLE IS SILVER PLATED, IT IS USED AS CATHODE.1. Electroplating is a process in which an object made up of a conducting material is coated with a

less actual metal using electrolysis technique.2. The article to be electroplated is used as cathode, the rod of metal to be coated is used as anode

and the electrolyte is a solution having cations of the metal to be coated.3. In the cathode reaction of the process, the metal ions move towards the cathode and accept

electrons from cathode to form metal atoms which get deposited on the object.4. Hence, when a brass article is silver plated, it is used as cathode.

10. WHEN ALUMINIUM ARTICLE IS ANODISED ITS SURFACE GETS BLACKENED.1. Anodising is a process used to make the aluminium surface resistant to corrosion and abrasion.2. Electrolyte used is dilute sulphuric acid and the aluminium article to be anodised is used as anode.3. The anode reaction results in formation of a black coloured thin film of aluminium oxide on the

surface of aluminium anode.

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4. Hence, when aluminium article is anodised its surface gets blackened.

11 K ITCHENWARE MATERIALS IS COATED WITH COPPER . 1. Kitchenware materials are generally made of stainless steel.2. They are coated with a thin layer of copper in order to protect them from rusting (corrosion) and

also to improve their appearance.

12. POTENTIAL DIFFERENCE OF SOURCE OF CURRENT (I .E . CELL ) IS LESS THAN E .M .F . ORT HE P.D. IS ALWAYS LESS THAN THE E .M .F . OF THE CELL . 1. In e.m.f. the cell has to spend energy to overcome its external resistance as well as the internal

resistance.2. In potential difference, the cell has to spend energy to overcome only its external resistance.3. As energy cell has some internal resistance, potential different of a source of current (i.e. cell) is

less than e.m.f.

3. THE PLATES OF HEATING DEVICES SUCH AS A TOASTER , AN ELECTRIC IRON ETC . ARE MADE OF ANALLOY RATHER THAN A PURE METAL . 1. A pure metal like copper has low resistance due to which it produces less heat.2. But alloys like nichrome have a very high resistance, thus the heat produced by it is more.3. Hence, in heating devices like a toaster, an electric iron etc., alloys are used instead of pure

metals.

14. A P ARALLEL COMBINATION OF RESISTANCES DECREASES EFFECTIVE RESISTANCE OF THE CIRCUIT . OR A PARALLEL COMBINATION IS USED TO DECREASE THE RESISTANCE OF A CIRCUIT .

1. In a parallel combination, the equivalent resistance is smaller than each of the individualresistances.

2. Therefore, a parallel combination is used to decrease the resistance of a circuit.

15. M ETALS ARE GOOD CONDUCTORS . OR M ETALS ARE GOOD CONDUCTORS OF ELECTRICITY . ORAN ELECTRIC CURRENT CAN FLOW THROUGH SILVER WIRE .

1. A metal contains large number of free electrons.2. When a metallic wire is connected between the two terminals (electrodes) of a cell, the

negatively charged free electrons flow from a point at a lower potential to a point at a higherpotential.

3. This motion of electrons in one direction constitutes an electric current.4. Hence, metals are good conductors of electricity.

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16. M OST OF THE ELECTRICAL APPLIANCES NEED EARTHING . 1. Connecting one end of a conducting wire to the metal body of the appliance and burying its

other end in the earth is called earthing. 2. If an electrical appliance is faulty, the live wire comes in contact with the metal body of the

appliance and the current flows in the body of that appliance.3. If the appliance is properly earthed, the current flowing through the metal body passes to the earth.4. Hence, there is no danger to the person handling that appliance.

17. F ILAMENT OF INCANDESCENT LAMP IS MADE OF TUNGSTEN . 1. Tungsten has a very high resistance. Thus, when an electric current passes through a filament of

Tungsten, it becomes extremely hot and emits light.2. Also Tungsten has a very high melting point due to which it can withstand the extreme heat and

does not melt.3. Hence, due to its high resistance and high melting point, Tungsten filament is used in

incandescent lamp.

18. F USE IS MADE OF A MATERIAL HAVING LOW MELTING POINT . 1. A fuse is a wire that is used as a safety device to protect electrical appliances from damages

caused due to excessive flow of current.2. It is made of an alloy of lead and tin has a low melting point.3. Thus, if the current exceeds a certain value, the fuse melts due to its low melting point and the

circuit is broken immediately.4. Thus in turn protects the appliances against any damages by limiting the current passing through it.

19. IN RAINY SEASON , WE SHOULD NOT TOUCH THE WALL OF A BUILDING . 1. In the rainy season, the walls of the buildings become wet due to rain or leakage of water.2. If a bare wire comes in contact with such a wet wall, the electric current begins to flow through

the wall since water is a good conductor of electricity.

3.

Hence, in the rainy season, we should not touch the wall of a building.

20. W HEN A COMPASS NEEDLE IS KEPT NEAR A WIRE CONDUCTING CURRENT , IT IS DEFLECTED . 1. When an electric current passes through a conductor, a magnetic field is produced around it.

Hence, if a compass needle is kept near such a conducting wire, it gets deflected

21. USE OF FOSSIL FUELS CREATED ENERGY CRISIS.1. Fossil fuels like coal, petroleum and natural gasses have been formed millions of years ago

under special circumstance.2. Since these conditions are not prevailing now, hence these fossils and fuels are rare.3. These energy sources are extensively used to meet our ever growing demands.

4. If we continue to use these non-renewable energy sources at present rate, their known reservewould deplete at very fast.5. Hence, use of fossil fuels creates energy crisis.

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22. MINI HYDROELECTRIC POSER STATIONS ARE PREFERRED. (14, MARCH 2008)1. Hydroelectric power plants can be constructed only at a limited number of places. Whenever a

dam is constructed, large land area gets submerged which causes long term problem of rehabilitation.

2. Besides being free from the problem of pollution, mini hydroelectric power plants are also freefrom issues and controversies that are associated with bigger dams.

3. Mini hydroelectric power stations can be constructed on rivers in the hilly regions.4. Hence, mini hydroelectric power stations are preferred.

23. WIND MILL REQUIRES SPECIFIC LOCATIONS.1. Wind energy is used to generate electricity by using wind mill. Electricity generated by a single

wind mill is quite small.2. To generate electricity on a commercial scale a large number of wind mills are erected over a

large area. This area is called as wind energy farm.3. Hence, wind mill requires a specific locations.

24. FARMERS WINNOW THE GRAINS.1. Wheat harvest contains husk.2. Winnowing helps in separation of the husk from the grains by using wind energy.3. Hence, farmers winnow the grains.

25. WE HAVE TO SEARCH FOR NEW RENEWABLE ENERGY SOURCES.1. Due to excessive industrialisation energy sources such as oil, coal and natural gas are undergoing fast

depletion.2. The growth in pollution, increase in energy demand and limited nature of conventional energy resources

has resulted in the energy crisis.3. Renewable energy resources are practically inexhaustible, non polluting and are available in distributed

manner4. To overcome these energy crises we have to search for new renewable energy resources .

26. The work done on an object by a conservative force is zero if it has come back to the samepoint from where it started.1. Works is associated with displacement since W = F x S2. If an object comes back to the same point from where it started, then its displacement is zero.

I.e. S = 0. Thus W = F x S = F x 0 = 0.3. Hence, if an object comes back to its original starting position, then the work done on the object is zero.

27. Potential energy of our body will be minimum when we lie down on the ground.1. The gravitational potential energy is conventionally taken to be zero at the ground level.2. Thus if we lie down on the ground, the potential energy of our body will be minimum.

28. Water stored in dams is used to generate electricity.1. Water stored in the reservoir of dam possesses gravitational potential energy since the reservoir is at a

height above ground level.2. As the water falls, it rotates the blades of turbines and work is done due to this potential energy.3. These turbines are connected to generators that generate electricity.4. Hence, water stored in dams is used to generate electricity.

29. Electric fan blades rotate when we put the switch ON.1. In the working of an electrical fan, electrical energy is converted into mechanical energy.2. When the switch is put ON, electricity reaches to the fan. This electrical energy is used to rotate the

blades of the electric fan and the fan is set into motion.3. Hence, the electric fan blades rotate when we put the switch ON.

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30. We use a pulley to draw water from the well.1. A pulley is a device that simplifies the task of lifting heavy loads, pulley are used in cranes,

building lifts, wells etc.2. When we use a pulley for removing water from a well, we pull one end of the rope in the

downward direction, i.e. in the direction of gravity.3. This act of pulling the rope in the downward direction easily raises the bucket which is full of water.4. Hence, a pulley is used to draw water from a well.

31. Power is a scalar quantity.1. Power is defined as the work done per unit time.2. Since work and time both are scalar quantities hence power also is a scalar quantity.

32. Vehicles having high, power can attain high speed.1. Power can also be expressed as the product of force and velocity (speed). Hence P = F x V.Hence, if the power of a vehicle is more, then the velocity (speed) of that vehicle will also be more

33. BATS CAN TRACE OUT PATH, EVEN IN THE DARK NIGHTS. OR BATS CAN FLY DURING NIGHTAVOIDING OBSTACLES

1. Bats are able to emit as well as hear ultrasonic sound (sound waves having frequency more than 20 kHz).2. While flying, bats emit ultrasonic sound. This sound is not audible to human beings.3. An ultrasonic sound gets reflected from the obstacles in their path.4. Bats hear the resulting echo enabling them to detect the obstacles, avoid collision and

change its path accordingly.5. Thus bats can trace out path even in the dark nights.

34. CURVED BOARDS ARE PLACED BEHIND A SPEAKER IN AN AUDITORIUM.1. Curved boards are placed behind a speaker in an auditorium to forward the sound waves that

otherwise spread in various directions and get lost.

2. Thus the boards prevent spreading out the sound waves in various directions.3. The board also sends the sound waves from a speaker at focus directly towards the audience

making a speech audible even at a distance.4. Hence, to make the sound more audible even at a great distance curved boards are placed

behind the speaker in an auditorium.

35. WE SEE THE FLASH OF LIGHTENING BEFORE A THUNDER IS HEARD .1. Velocity of light in air (3 x 10 8 m/s) is much greater then the velocity of sound in air (340

m/s) at room temperature.2. Due to this the flash of lightening is seen almost immediately after the occurrence of lightening.3. While sound takes certain time to reach the observer.4. Thus, we can see the flash of lightening before the thunder is heard.

36 . THE VELOCITY OF SOUND IS AFFECTED BY WIND VELOCITY.1. When sound travels in the direction of the wind, the observed velocity of sound is greater.

This is because the velocity of sound is equal to sum of the actual velocity of sound andvelocity of the wind.

2. On the other hand, when sound travels in a direction opposite to that of the wind, theobserved velocity of sound will be lower because effective velocity of the sound will be thedifference of velocity of sound and velocity of the wind.

3. If the wind is blowing in a direction inclined to the direction of the sound, the effectivevelocity of the sound is affected by components of the wind velocity in the direction of velocity of the sound.

4. Thus, the velocity of sound is affected by wind velocity.

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37. WHISTLE OF A PASSING TRAIN IS CLEARLY HEARD ON A QUIET MISTY NIGHT.1. The velocity of sound in moist air is greater than the velocity of sound in dry air.2. Therefore an increase in humidity increases the velocity of the sound in air.3. At night when humidity tends to rise, the sound travels faster and can be heard more clearly

on a quiet misty night.4. Thus, whistle of passing trains is clearly heard on a quiet misty night.

38. If a piece of ice is dropped into a glass of water, it floats on the surface of the water.1. Ice is the solid form of water but its density is much less than that of water.2. We know as water cools below 4 0 C its volume increases.3. As a result density of ice is less that that of water and so it floats on the surface of the water.

39. In winter the pipeline carrying, water burst in cold countries.1. In cold countries during winter, the temperature of the atmosphere falls below 0 0 C.2. When the temperature of water falls below 4 0 C, it expands.3. Hence, the water in pipes freezes and expands. As there is no room for expansion, water exerts

a large pressure on the pipes.Hence, the pipes sometimes burst.

40. When a water bottle is kept in the freezer (deepfreeze) compartment of a refrigerator, it burst.1. The temperature of air in the freezer (deepfreeze) compartment of a refrigerator is less than 0 0C.2. When a water bottle is kept in this compartment, the temperature of water falls below 4 0C and

the water expands. It exerts pressure on the sides of the bottle since there is no room forexpansion the bottle bursts.

41. A white trails may be seen behind high flying aircraft.1. When an aircraft is flying at a very high altitude, the water vapour from its engine condenses to form fog.2. This fog appears in the form of a white trail behind the high flying air craft.3. Hence, a white trail is visible behind high flying aircrafts.

42. during cold nights, sometimes dew is formed. (March 2008)3. On a cold clear night, the energy escapes from the surface of the earth and the temperature of

the ground reduces considerably.4. The cold ground cools the air in contact with it and the temperature of air falls below the dew

point leading to dew formation.5. Hence, during cold nights, sometimes dew is formed.

43. A stick dipped in water obliquely appears bent at the surface of water. .

Answer.a. When a straight stick is partly immersed in water and held in a slanting position, the rays of light coming

from the immersed part of the stick emerge from water (denser medium) and enter air (rarer medium).

During this propagation, they bend away from the normal on refraction.b. As a result, the immersed part of the stick does not appear straight with respect to the part outside the water,

but appears to be raised.Hence, a stick dipped obliquely in water appears bent at the surface of water .

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44. particles show less deflection as compared to particles1. particles are heavy mass particles as compared to particles.2. Hence particles show less deflection as compared to particles.

45. y- radiations are not deflected by electric or magnetic field.1. y- Radiations are electromagnetic waves of short wave length.2. They do not have any charge.3. Hence, they are not deflected by electric or magnetic field.

46. Radioactive transformation does not take place when an atom emits y rays.1. y rays are electromagnetic waves of very short wave length.2. They do not have charge or mass.3. Therefore, when y ray is emitted by a radioactive atoms, there is not change is its mass

number or atomic number.4. Hence, radioactive transformation does not take place when an atom emits y rays.

47. X rays are invisible1. X Rays are electromagnetic waves having very short wavelength of 5 x 10 -8m to 5 x 10 -15 m.2. Wavelength of 4 x 10 -7 m to 7 x 10 -7 m is visible.3. Hence, x rays are invisible.

48. X rays can penetrate through skin but not through bones.1. Bones are made up of calcium phosphate.2. X rays can penetrate through materials like skin and flesh but can not penetrate through

dense materials like calcium.3. Hence, X rays can penetrate through skin but not through bones.

49. Exposure of X rays for a long time should be avoided.3. X rays are used to kill dangerous cells and tumours in the body.4. At the same time cal also kill the healthy cells and tissues causing harm to the body.5. Hence, exposure of x rays for a long time should be avoided.

50. X rays are used to detect fracture of bones.1. X Rays can penetrate through skin and flesh but cannot penetrate through dense materials like bones.2. Due to this property X rays can provide a clear image of the bone and hence they are used to

detect fracture of bones.

51. X rays are used in industries.1. The penetrating power of X rays is very high.2. Therefore X rays are used to detect flaws of defects in metal castings and welding.3. Hence, X rays are used in industries.

52. X rays are used to detect smuggled of gold or silver.1. X Rays cannot penetrate through dense materials like gold and silver.2. Due to this property X rays can reveal the presence of hidden gold or silver.3. Hence, they are used to detect smuggled of gold and silver.

53. It is difficult to achieve controlled fusion reaction in the laboratory.

1. Fusion reactions take place only at a very high temperature of the order of 109 0

C.2. Such a high temperature exists only in the interior of the sun and other stars.

So it is difficult to achieve controlled fusion reaction in the laboratory.

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TRANSITION AND INNER TRANSITION ELEMENTS.T RANSITION ELEMENTS INNER TRANSITION ELEMENTS

1. In the atoms of transition elements the lasttwo shells are incompletely filled.

2. These elements are placed in B groupsof modern periodic table.

3. They are included in d-block of modernperiodic table.

1. 1In the atoms of these elements the last threeshells are incompletely filled.

2. These elements are placed in two additionalrows called series, placed separately at thebottom of the modern periodic table.(lanthanides and actinides)

3. They are included in f block of modernperiodic table.

2. S BLOCK ELEMENTS AND P BLOCK ELEMENTS.S-BLOCK ELEMENTS P-BLOCK ELEMENTS

1. In modern periodic table the group IA andgroup IIA together with hydrogen formthe s block elements.

2. These include Alkali metals and Alkalineearth metals.

3. They have 1 or 2 electrons in the last shell .

1. In modern periodic table the group IIIA togroup VII A and the zero groups form the p block elements.

2. These include metals, non metals andmetalloids.

3. They have 3 to e electrons in the last shell.

3. ELECTROLYTE AND NON ELECTROLYTE.ELECTROLYTE NON ELECTROLYTE

1. A substance whose aqueous solution canconduct electric current is calledelectrolyte.

2. Electrolytes are electrovalent compounds.

3. All the acids, bases and salts areelectrolytes.

1. A substance whose aqueous solution cannotconduct electric current is called non electrolyte.

2. Non electrolytes are covalent compounds.

3. Organic compounds such as glucose, urea,cane sugar and alcohol are non electrolytes.

4. CATHODE AND ANODECATHODE ANODE

1. The electrode connected to the negativeterminal of a battery is called cathode.

2. During electrolysis cations move towardscathode.

3. Cathode is that electrode at which electronsenter the electrolyte.

1. The electrode connected to the positiveterminal of a battery is called anode.

2. During electrolysis anions move towardsanode.

3. Anode is that electrode at which electronsleave the electrolyte.

5. ELECTRIC CURRENT THROUGH METALS AND ELECTRIC CURRENT THROUGH ELECTROLYTE .E LECTRIC CURRENT THROUGH METALS E LECTRIC CURRENT THROUGH ELECTROLYTE

1. The conduction of electric current throughmetals is due to flow of free electrons.

2. In metals free electrons flow from point of lower potential to point of higher potential.

3. Conduction of electric current throughmetals is possible for unlimited timeperiod.

4. e.g. electric bulbs, electric motor, electricaldevices etc.

1. The conduction of electric current throughelectrolytes conductors is due tomovements of ions ( cations and anions )

2. In electrolytes, the electrons enter theelectrolyte through cathode and leave theelectrolyte through anode.

3. Conduction of electric current throughelectrolyte is possible only for limited timeperiod.

4. E.g . dry cells, car batteries, techniques suchas electrolysis, electroplating and anodizing.

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6. CATHODE REACTION AND ANODE REACTIONC ATHODE REACTION ANODE REACTION

1. During electrolysis, the chemical changesoccurring at cathode are represented bycathode reaction.

2. In cathode reaction cations accept electronsavailable at cathode.

3. Electroplating of an article is the result of cathode reaction.

1. During electrolysis, the chemical changesoccurring at anode are represented by anodereaction.

2. In anode reaction, anions lose electrons tothe anode.

3. Anodising of an article is the result of anode reaction.

7. ELECTROPLATING AND ANODISINGE LECTROPLATING ANODISING

1. Electroplating is a process in which an objectmade up a conducting material, is coated witha less active metal using electrolysistechnique.

2. Electroplating can be done on metals andalloys such as iron, steel, brass, silver etc.

3. The article to be electroplated is used as acathode.

4. Electroplating of an article is the result of cathode reaction.

5. Electrolyte used is a solution having cations of the metal which is to be plated.

1. Anodising is a process used to make thealuminium surface resistant to corrosion andabrasion using electrolysis technique.

2. Anodising can be done only on aluminium.

3. The article to be anodised is used as an anode.

4. Anodising of an article is the result of anodereaction.

5. Electrolyte used is dilute sulphuric acid.

8. ACID AND BASEACID BASE

1. The substance which gives hydrogen ions(H +) when dissolved in water is called anacid.

2. Number of replaceable hydrogen present inacid is called basicity of acid.

3. The relation between Normality andMolarity of an acid is given by the formulaNormality = Basicity x molarity

1. The substance which gives hydroxyl ions(OH- ) when dissolved in water is called abase.

2. Number of replaceable hydroxyl grouppresent in based is called acidity of base.

3. The relation between Normality andMolarity of a base is given by the formulaNormality = Acidity x Molarity

9. NORMALITY AND MOLARITY

NORMALITY MOLARITY1. Normality of a solution is based on theequivalent weight of the solute.

2. The Normality of the solution is thenumber of gram equivalent weight of solute present per litre of its solution.

1. Molarity of a solution is based on themolecular weight of the solute.

2. The Molarity of a solution is the number of moles of solute dissolved per litre of solution.

10. VOLTMETER AND AMMETERVOLTMETER AMMETER

1. It is a device used to measure the potentialdifference between two points.

2. It is connected in parallel with the cell.3. It has a very high resistance.

1. It is a device used to measure the currentflowing through the circuit.

2. It is connected in series with the cell.3. It has a very low resistance.

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11. RESISTANCE IN SERIES AND RESISTANCES IN PARALLEL COMBINATION. R ESISTANCE IN SERIES R ESISTANCES IN PARALLEL

1. 1. If a number of resistances are connectedin such a way that the same current flowsthrough each resistance, then thearrangement is called Resistances in Series.

2. The voltage across each resistance isdifferent.

3. This combination is used to increase theresultant resistance of the circuit.

4. This combination decreases the current inthe circuit.

1. If a number of resistances are connectedbetween two common points such that thepotential difference across each is the same,then that arrangement is called Resistancesin Parallel.

2. The current across each resistance isdifferent.

3. This combination is used to decrease theresistance of the circuit.

4. This combination increases the current in thecircuit.

12. E.M.F. AND P.D.E.M.F. P.D.

1. It is the work done by the source ( cell ) inraising a unit positive charge from its lowpotential and end to its high potential unit.

2. It is greater than the P.D. of the cell.

1. It is the energy spent by a cell to send a unitpositive charge across the external circuit.

2. It is less than the E.M.F . of the cell.

13. RENEWABLE ENERGY SOURCES AND NON RENEWABLE ENERGY SOURCES.R ENEWABLE ENERGY SOURCES NON R ENEWABLE ENERGY SOURCES

1. The resources which have inherent capacity toreappear or replenish themselves within areasonable time are called as renewable energyresources.

2. These resources are generally environmentalfriendly and dont pollute environment.

3. E.g. Energy obtained from biomass, biogas, biofuels etc.

1. Those resources which once used are lost forever and cant be replenished are called as non renewable as non renewable energy resources.

2. These resources cause pollution.

3. E.g. Fossil fuels like coal, petroleum.

14. FOSSIL FUEL ENERGY AND SOLAR ENERGY.FOSSIL FUEL ENERGY SOLAR ENERGY

1. Fossil fuels are not available abundantly allover the world.

2. The use of fossil fuels leads to pollutions andother environmental problems.

3. Fossil fuels are available in limitedquantities and hence they are available forlimited time.

1. Solar energy is freely available on a largescale all over the world.

2. The use of solar energy does not lead to anypollution and other environmental problems.

3. Solar energy will be available for millions of years.

15. BIOMASS - BIOGASBIOMASS BIOGAS

1. Biomass is the material contained in thebodies of plants and animals.

2. Burning of biomass produces smoke.

1. Biogas is a fuel produced by microbialdecomposition of organic matter in absenceof oxygen.

2. Burning of biogas does not produce any

smoke.

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16. K INETIC ENERGY AND P OTENTIAL ENERGY .K INETIC E NERGY P OTENTIAL ENERGY

1. It is the energy possessed by a body due toits motion.

2. It occurs only in one form and does not haveto be converted into any other form in orderto perform work.

3. Kinetic energy is given by formula,KE=1/2mv 2.

4. E.g. Bullet fired from a gun, Flowing wateretc.

1. It is the energy possessed by a body due toits position or configuration.

2. It occurs in various forms but to performwork, it has to be converted into kineticenergy.

3. Potential energy is given by formula,PE=mgh.

4. E.g. compressed spring, Water stored in areservoir.

17. ENERGY AND POWERENERGY POWER

1. Energy is defined as the stored ability of a

body to do work.

2. S.I. unit of energy is joule.

1. Power is defined as the work done per unit

time.

2. S.I. unit of powers is J/s (Watt).

18. SOUND AND NOISESOUND NOISE

1. Sound propagates in air in the form of longitudinal waves.

2. It does not produce a disturbing andannoying effect on our ear.

1. Noise has an irregular wave form.

2. Noise produces a disturbing and annoyingeffect on the ear.

19. ABSOLUTE HUMIDITYV/S RELATIVE HUMIDITY

ABSOLUTE HUMIDITY RELATIVE HUMIDITY1. The mass of water vapour per unit volume of

air is called absolute humidity.

2. It is expressed in g/m 3.

3. It conveys the amount of water vapour presentin the air.

1. Relative humidity is the ratio of actual massof water vapour present in a given volume of air to the mass of water vapour required tosaturate the same volume at the sametemperature.

2. It is expressed as a percentage.3. It conveys how close the amount of watervapour in the air is to the saturation level of air at that temperature.

20. CONVEX LENS AND CONCAVE LENSCONVEX LENS CONCAVE LENS

1. A convex lens is thicker at the centre than atthe edges.

2. It is a converging lens.3. Image formed by convex lens is usually real,

inverted and magnified, except when theobject is within the focal length of the lens.

1. Concave lens is thinner at the centre than atthe edges.

2. It is diverging lens.3. Image formed by a concave lens is always

virtual, erect and diminished.

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21. SHORT SIGHT (MYOPIA) AND LONG SIGHT (HYPERMETROPIA)SHORT SIGHT (MYOPIA) LONG SIGHT (HYPERMETROPIA)

1. Myopia arises due to slight elongation of theeyeball or due to the eye lens so that thedistance between the eye lens and retina ismore than that in the case of a normal eye.

2. Distant object are not seen clearly.3. The lens becomes more curved or eyeball is

elongated.4. The distance between lens and retina is more

than normal.5. Rays of light from distant object meet in front

of the retina.6. It can be corrected by concave lens.

1. Hypermetropia arises due to slight flatteningof the eyeball so that the distance between theeye lens and retina is less than that in the caseof a normal eye.

2. Nearer objects are not seen clearly.3. The lens becomes less curved or eyeball is

flattened.4. Distance between lens and retina is less than

normal.5. Rays of light from nearer objects meet behind

the retina.6. It can be corrected by convex lens.

22. HYPERMETROPIA AND PRESBYOPIA.HYPERMETROPIA PRESBYOPIA

1. Hypermetropia arises due to slight flatteningof the eyeball.

2. In this case, there is no weakening of theciliary muscles.

1. In Presbyopia, there is no defect in the shapeof the eyeball.

2. This defect arises due to weakening of theciliary muscles.

23. MYOPIA AND PRESBYOPIAMYOPIA PRESBYOPIA

1. Myopia arises due to slight elongation of theeyeball or due to the eye lens so that thedistance between the eye lens and retina ismore than that in the case of a normal eye.

2. In this case, there is no weakening of theciliary muscles.

3. This defect is corrected using spectacles of concave lenses

1. In Presbyopia, there is no defect in the shapeof the eyeball.

2. This defect arises due to weakening of theciliary muscles

3. This defect is corrected using spectacles of convex lenses.

24. COMPOUND MICROSCOPE AND REFRACTING TELESCOPECOMPOUND MICROSCOPE(Astronomical

telescope)REFRACTING TELESCOPE(Astronomical

refracting telescope)1. The focal length of objective is less than

eyepiece.

2. The object is kept just beyond F of the objectlens

3. It is used to magnify the image of given object

4. It is used by pathologist to observe bloodcells, plants and animal cells.

1. The focal length of objective is more thaneyepiece.

2. The object is very far beyond 2F of the objectlens.

3. It is used to produce a near image of a distantobject.

4. It is used by astronomers to observe stars,planets, satellites, nebulae, etc.

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25. COMPOUND MICROSCOPE AND SIMPLE MICROSCOPE (MAGNIFYING LENS)COMPOUND MICROSCOPE SIMPLE MICROSCOPE

(MAGNIFYING LENS)1. In a compound microscope, two convex

lenses are used.2. The object is placed beyond the focal length

of the objective3. Its magnifying power is much greater than

that of a simple microscope.4. It is used to observe blood corpuscles, plant

and animal cells, etc.

1. In a simple microscope, only one convex lensis used.

2. In this case, the object is placed within thefocal length of the convex lens.

3. Its magnifying power is much less than that of a compound microscope.

4. It is used to observe minute parts of a watch,to read words in small print, etc.

26. SIMPLE MICROSCOPE AND ASTRONOMICAL TELESCOPESIMPLE MICROSCOPE ASTRONOMICAL TELESCOPE1. In a simple microscope, only one convex lens

is used.2. In this case, the object is placed within the

focal length of the convex lens.3. In this case, the image is erect.4. It is used to observe minute parts of a watch,

to read words in small prints, etc.

1. In an astronomical telescope, two convex

lenses are used.2. In this case, the object is far away from the

objective.3. In this case, the image is inverted.4. It is used to observe satellites, planets, stars,

etc.

27. PARTICLES AND PARTICLES. PARTICLES PARTICLES

1. particles are positively charged heliumnuclei.

2. They carry a charge of 3.2 x 10 -19C.3. particles have velocity ranging from 10 6

m/s to 10 7 m/s.4. The penetrating power of particles is

small i.e. 1/10000 times of y rays.5. When an atom of a radioactive element

emits a particles the mass numberdecreases by 4 and atomic number decreasesby 2.

1. Particles are negatively chargedelectrons.

2. They carry a charge of -1.6 x 10 -19C.3. Particles have velocity equal to 99 % of

the velocity of light.4. The penetrating power of - particles is

1/100 times of y rays.5. When an atom of a radioactive element emits

a a particle, its mass number remains thesame and its atomic number increases by 1.

28. PARTICLES AND Y RAYS. PARTICLES Y RAYS

1. particles are positively charged heliumnuclei.

2. The penetrating power of particles issmall i.e. 1/10000 times of y rays.

3. Ionising power of particles is very highi.e. 10000 times of y rays.

4. When an atom of a radioactive elementemits a particles its mass number

decreases by 4 and atomic number decreasesby 2.

1. y Rays are electro magnetic waves.

2. The penetrating power of y rays ismaximum.

3. Ionizing power of y rays is very small ascompared with particles.

4. When an atom of a radioactive element emitsy rays its mass number and atomic number

do not change.

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29. PARTICLES AND Y RAYS. PARTICLES Y RAYS

1. Particles are negatively charged.2. The penetrating power of particles is less

than y rays.3. Particles are deflected in electric and

magnetic field.4. When an atom of a radioactive substance

emits particle its mass number remains thesame and its atomic number increases by 1.

1. y Rays are electro magnetic waves.2. The penetrating power of y rays is greater

than particles.3. y Rays are not deflected in electric and

magnetic field.4. When an atom of a radioactive element emits

y rays its mass number and atomic numberdo not change.

30. CATHODE RAYS AND X RAYS.CATHODE RAYS X RAYS

1. Cathode rays are made up of negativelycharged particles.

2. Cathode rays deflect in electric and magneticfield.

3. Cathode rays can pass through thin foils of metals.

1. x Rays are electromagnetic waves of shortwavelength.

2. X Rays do not deflect in electric andmagnetic field.

3. X Rays can pass through thin sheet of metals.

31. NUCLEAR FUSION AND NUCLEAR FISSIONNUCLEAR FUSION NUCLEAR FISSION

1. Production of energy when two lighternuclei fuse or combine together to form aheavy and stable nucleus is called nuclearfusion.

2. The energy liberated during a single nuclearfusion is less as compared to the energyliberated during a single nuclear fission.

3. Nuclear fusion takes place at a very hightemperature i.e. (10 9) 0C.

4. Controlled nuclear fusion is very difficult tobe achieved at the surface of the earth.

1. Splitting up of a heavy nucleus into lighternuclei with release of large amount of energyis called as nuclear fission.

2. The energy liberated during a single nuclearfission is very large.

3. Nuclear can take place at a normaltemperature.

4. Controlled nuclear fission forms basis of atomic reactor.

32. CONTROLLED CHAIN REACTION AND UNCONTROLLED CHAIN REACTION.CONTROLLED CHAIN REACTION UNCONTROLLED CHAIN REACTION

1. The nuclear chain reaction in which most of the neutrons liberated in the chain reactionare absorbed is called as controlled chainreaction.

2. In this reaction most of neutrons areabsorbed using boron steel or cadmium rods.

3. In this reaction, the rate of disintegration of atom is controlled.

4. This reaction is used for constructivepurposes like generating electricity.

1. The self accelerating chain reaction whichtakes place on its own accord is called auncontrolled chain reaction.

2. In this reaction neutrons are not absorbed.

3. The rate of disintegration of atom is notcontrolled.

4. This reaction is used for destructive purposeslike atom bomb.

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33. PERIODS AND GROUPSPERIODS GROUPS

1. The horizontal rows of elements in themodern periodic table are called as periods.

2. There are seven periods in the modernperiodic table.

3. The period number indicates the number of electronic shell present in an atom.

4. Elements show gradual variation in chemicalproperties along a period.

1. The vertical columns of elements in themodern periodic table are called as groups.

2. There are eighteen groups in the modernperiodic table.

3. The group number indicates the number of electrons in the outermost shell of an atom.

4. Elements belonging to a particular groupshow strong resemblance (similarity) in theirchemical properties.

34. MENDELEYEV PERIODIC TABLE AND MODERN PERIODIC TABLEMENDELEEVS PERIODIC TABLE MODERN PERIODIC TABLE

1. Mendeleevs periodic table is based on theatomic weight of the elements.

2. In Mendeleevs periodic table, elements werearranged in an increasing order of atomicweights.

3. In Mendeleevs periodic table, there are 8 groups.

4. In Mendeleevs periodic table, there are 7periods.

5. Mendeleevs periodic table is not divided intoany blocks.

1. Modern periodic table is based on the atomicnumber of the elements.

2. In Modern periodic table, elements are arrangedin an increasing order of atomic numbers.

3. In modern periodic table, there are 18 groups.4. Apart from the seven periods, there are two

additional rows called series placed separately atthe bottom of Modern periodic table.

5. Modern periodic table is divided into fourblocks, names as s-block, p-block, d-block and f-block.

35. INERT GAS ELEMENTS AND NORMAL ELEMENTS.INERT GAS ELEMENTS NORMAL ELEMENTS1. In the atoms of these elements all the shells are

completely filled including the outermost shell.2. These elements are placed in zero group of

modern periodic table.3. These elements have stable electronic

configuration and hence they are chemicallyinactive.

4. Their valency is zero.5. They are included only in p-block of modern

periodic table.

1. In the atoms of these elements only theoutermost shell is incompletely filled.

2. These elements are placed in A groups . i.e. IAto VIIA of modern periodic table.

3. These elements do not have stable electronicconfiguration and hence they are chemicallyactive.

4. They normally show one type of valency.5. They are included in s-block and p-block of

modern periodic table.

37. NORMAL ELEMENTS AND TRANSITION ELEMENTSNORMAL ELEMENTS TRANSITION ELEMENTS

1. In the atoms of these elements only theoutermost shell is incompletely filled.

2. These elements are placed in A group. i.e.IA to VIIA of modern periodic table.

3. They normally show one type of valency.4. They are included in s-block and p-block of

modern periodic table.5. The compounds of these elements aregenerally colourless.

1. In the atoms of these elements the last twoshells are incompletely filled.

2. These elements are placed in B groups. i.e.IIIB to IIB along with VIII group (Groups8,9,10) of modern periodic table.

3. They show variable valency.4. They are included in d block of modern

periodic table.5. The compounds of these elements aregenerally coloured.

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38. INERT GAS ELEMENTS AND TRANSITION ELEMENTS.INERT GAS ELEMENTS TRANSITION ELEMENTS

1. In the atoms of these elements all the shells arecompletely filled including the outermost shell.

2. These elements are placed in zero group of

modern periodic table.

3. These elements have stable electronicconfiguration and hence they are chemicallyinactive.

4. Their valency is zero.5. They are included in p block of modern

periodic table.

1. In the atoms of these elements the last two shellsare incompletely filled.

2. These elements are placed in B groups. i.e. IIIB

to IIB along with VIII group (Groups 8,9,10) of modern periodic table.3. These elements do not have stable electronic

configuration and hence they are chemicallyactive.

4. They show variable valency.5. They are included in d block of modern periodic

table.39. ALKALI METALS AND ALKALINE EARTH METALS.

ALKALI METALS ALKALINE EARTH METALS1. In the modern periodic table, the elements in

group IA excluding hydrogen, are called asAlkali metals.2. Atoms of these elements have one electron

in the valence shell.3. They are monovalent.4. e.g. Li, Na, K etc.

1. In the modern periodic table, the elements in

group IIA are called as Alkaline earthmetals.2. Atoms of these elements have two electrons

in the valence shell.They are divalent.

3. e.g. Be, Mg, Ca etc.

40. D BLOCK ELEMENTS AND F BLOCK ELEMENTS.D - BLOCK ELEMENTS F BLOCK ELEMENTS

1. In modern periodic table, the group III B togroup II B along with group VIII (group

8,9and 10) form, the d block elements.

2. These include transition elements.

3. They have their last two shells incompletelyfilled.

4. e.g. Sc, Ru, Rh etc.

1. In modern periodic table the two additionalrows placed separately at the bottom of the

table are called series and together theelements of these series form the f block elements.

2. These include inner transition elementslanthanides and actinides.

3. They have their last three shells incompletelyfilled.

4. e.g. La, Lu, Lr etc.

41. ANODE AND CATHODEANODE CATHODE

1. The positively charged electrode in anelectrolytic cell is known as anode.

2. Negative ions (anions) are attracted to it.

1. The negatively charged electrode in anelectrolytic cell is known as cathode.

2. Positive ions (cations) are attracted to it.

42. OHMIC CONDUCTORS AND NON OHMIC CONDUCTORS.O HMIC C ONDUCTORS NON O HMIC C ONDUCTORS

1. Materials that obey Ohms Law are calledOhmic Conductors.

2. For e.g. Copper

3.

It has a Linear current voltage relationship.4. The value of the resistance (R) is constant.

1. Materials that do not obey Ohms Law arecalled Non Ohmic Conductors.

2. For. e.g. Diodes

3.

It has a non linear current voltagerelationship.4. The value of the resistance is variable.

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43. POTENTIAL DIFFERENCE AND ELECTRIC CURRENT.POTENTIAL DIFFERENCE (P.D.) ELECTRIC CURRENT

1. The difference between the electric levels of the terminals of a conductor is known aspotential difference.

2. Its S.I. unit is Volt.

1. The flow of electric charge is calledelectric current.

2. Its S.I. unit is Ampere.

44. EQUIVALENT RESISTANCE IN SERIES AND EQUIVALENT RESISTANCE INPARALLEL.

EQUIVALENT RESISTANCE IN SERIES EQUIVALENT RESISTANCE INPARALLEL

1. The equivalent resistance of a seriescombination is equal to the sum of theindividual resistances.

2. The equivalent resistance in series is greaterthan the individual resistances.

1. The reciprocal of the equivalent resistancein parallel is equal to the sum of thereciprocals of the individual resistances.

2. The equivalent resistance in parallel issmaller than the individual resistances.

45. FLOW OF ELECTRIC CURRENT THROUGH A METAL AND FLOW OF ELECTRICCURRENT THROUGH AN ELECTROLYTE.

FLOW OF CURRENT THROUGH AMETAL

FLOW OF CURRENT THROUGH ANELECTROLYTE

1. The electric current flows due to the motionof free electrons.

2. The flow of chare is unidirectional.3. No chemical change occurs in the substance

carrying the current.

1. The electric current flows due to the motionof ions.

2. The flow of charge is bi directional.3. Chemical change occurs in the substance

carrying the current.

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DIAGRAM 1. E LECTROPLATING ASSEMBLY.

2. E LECTROLYSIS OF COPPER CHLORIDE USING CARBON ELECTRODES.

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3. T ESTING E LECTRIC CONDUCTION OF SOLUTIONS

4. ANODISING TECHNIQUE

5. ATOMS OF HYDROGEN AND LITHIUM .

6. SIMPLE VOLTAIC CELL .

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7. VERIFICATION OF O HM S LAW .

8. C ONNECTION DIAGRAM OF THREE RESISTANCES IN PARALLEL

9. G RAPH OF CHARACTERISTICS OF DIODE AND T HERMISTORS .

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10. C ONNECTION DIAGRAM OF THREE RESISTANCES IN SERIES .

11. C ONNECTION DIAGRAM OF THREE RESISTANCES IN PARALLEL .

12. L INES OF MAGNETIC FIELD DUE TO A STRAIGHT CONDUCTOR CARRYING CURRENT .

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13. L INES OF MAGNETIC FIELD AROUND SOLENOID CARRYING CURRENT .

14. H EATING EFFECT OF ELECTRIC CURRENT VERIFICATION OF J OULE S LAW .

15. O RESTED S EXPERIMENT FOR MAGNETIC EFFECT OF ELECTRIC CURRENT .

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16. T ELEPHONE EAR PIECE .

17. WORKING OF ELECTRIC BELL .

18. BIO GAS PLANT

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19. THE INNER SURFACE OF SOLAR COOKER BOX IS PAINTED BLACK.

20. THE STORAGE TANK IN A SOLAR WATER HEATER IS KEPT AT HIGHER LEVEL.

21. E XPLAIN H OPE S APPARATUS WITH THE HELP OF NEAT AND LABELLED DIAGRAM .

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22. Describe an experiment to show that the quantity of heat given out by the bodies, having the samemass but made of different substances, when thy cool through the same temperature range isdifferent in each case.

23. WRITE A NOTE ON HUMAN EYE.Answer.

24. SIMPLE MICROSCOPE

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25. Describe construction of compound microscope and draw a ray diagram showing the formatof an image by a compound microscope.

Ans.

26. Experiment with diagram to show that radioactive substances emit three kinds of radiation.

27. Explain CHAIN REACTION with an example.Ans.

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28. PRODUCTION OF CATHODE RAYS. (pg. no. 204)

29. WIND MILL

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ANSWER IN BRIEF 1. MOSELEYS CONTRIBUTION AND THE MODERN PERIODIC TABLE.

M OSELEY S CONTRIBUTION . 1. In 1913, Henry Moseley , an English physicist, found that it was the atomic number (Z) and not

the atomic mass, which was the fundamental property of an element, useful for an arrangement inthe periodic table.

2. At that time, the atomic number of an element signified only the ordinal number of that elementas it appeared in the periodic table.

3. Moseley recognized that the ordinal number of an element in periodic table is same as its nuclearcharge which is its atomic number.

M ODERN PERIODIC TABLE1. The modern periodic table is also called the long form of periodic table.2. In modern periodic table the elements are arranged in increasing order of atomic number (Z).3. The modern periodic table contains seven horizontal rows called periods.4. There are eighteen vertical columns called groups.5. Apart from the seven rows, there are two additional rows called series, placed separately at the bottom of the table .6. The entire table is divided into four blocks, named as s block, p-block, d block and f block.7. On the basis of electronic configuration, the elements are classified into four types viz. normal

elements, inert elements, transition elements and inner transition elements.

2. H ALOGEN GROUP ELEMENTS .

1.

The VII A group in the periodic table is a family of halogens.2. The members of this group from top to bottom are as given in the table.Group VII A

elementsSymbol Atomic

Number (Z)Electronic

configurationValency Physical state

FluorineChlorineBromine

IodineAstatine

FClBrI

At

917355385

2,72,8,7

2,8,18,72,8,18,18,7

2,8,18,32,18,7

11111

GasGas

LiquidSolidSolid

3. The valence shell halogen contains seven electrons.4. This makes the valency of halogen one (monovalent).5. The compounds of halogens with hydrogen are HF, HCl, HBr, etc.6. In ordinary conditions Fluorine and Chlorine are gases, Bromine is a liquid while Iodine and

Astatine are solids.

3. Z IG Z AG LINE IN MODERN PERIODIC TABLE .

1. On the basis of electronic configuration of elements, the periodic table is divided into four blocks, viz, s-block, p-block, d-block and f block.

2. The elements of s-block ( except hydrogen ) d-block and f-block are all metals.3. In the p-block all the three types of elements i.e. metals, non metals and metalloids, are present and these

elements are separated by a zig zag line.

4.

In the p-block of a modern periodic table, a zig zag line separates the metals on the left side from thenon metals on the right side.5. The bordering elements along the zig zag line are the metalloids. These are Boron ( B), Silicon (Si),

Germanium 9Ge), Arsenic ( As), Antimony ( Sb ), tellurium ( Te ) and Polonium ( Po ) and astatine (At).

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4. DESCRIBE THE FOUR BLOCKS OF THE PERIODIC TABLE BASED ON THE ELECTRONICCONFIGURATION OF ELEMENTS . (14, MARCH 2008)

.1. The distribution of electrons in the various shells around the nucleus of an atom of an

element is called as its electronic configuration.2. Based on this electronic configuration of elements, the modern periodic table is divided into

four blocks viz. s-block, p-block, d-block and f-block.a. S-block : - The group IA and group IIA together with hydrogen form the s-block elements.

They have 1 or 2 electrons in the last shell. The elements of s-block (except hydrogen) are allmetals.

b. P-block : - The group III A to group VII A and the zero groups together constitute the p-block elements. They have 3 to 8 electrons in the outermost shell. In the p-block all the threetypes of elements such as metals, non metals and metalloids are present.

c. d-block : - The group III B to II B along with VIII group (group8, 9 and10) together arecalled d block elements. They have their last two shells incompletely filled. They are calledtransition elements. They are all metals.

d. f-block : - The two series at the bottom of the periodic table (the lanthanides and theactinides) together form the f-block elements. They have their last three shells incompletelyfilled. They are called as inner transition elements. They are all metals.

5. STATE ANY FOUR MAIN FEATURES OF THE LONG FORM OF PERIODIC TABLE .

FF EE AATT UURR EE SS OO FF TT HH EE LL OO NN GG FF OO RR MM OO FF PP EE RR II OO DDII CC TT AABBLL EE .. 1.

The basis of modern periodic table is the atomic number (Z).2. The position of an element in the modern periodic table is based on its electronic configuration.3. The modern periodic table contains seven horizontal rows called periods and eighteen vertical

columns called groups.4. Apart from the seven rows, there are two additional rows called series, placed separately at the

bottom of the table.5. On the basis of electronic configuration, the elements are classified into four types viz. normal

elements, inert elements, transition elements and inner transition elements.6. On the basis of electronic configuration of elements, the periodic table is divided into four

blocks viz. s-block, p-block, d-block and f-block.

6. E LECTROLYSIS OF COPPER CHLORIDE

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Construct an electrolytic cell using 150 ml aqueous solution of 2g copper chloride as electrolyte andtwo carbon rods as electrodes. Connect a 6 volt battery, a switch and a bulb in the electric circuitproperly. Switch on the current in the circuit. The bulb starts glowing indicating that the beakercontains an electrolyte. Pass the current through the solution for some more time ( about 15 min ) andobserve the changes. Two important observations can be noted in this demonstration.

1. C HANGES AT THE E LECTRODES : - The portion of the cathode dipped in the electrolyte becomesreddish. Bubbles of some gas are formed at the anode.

2. C OLOUR OF THE ELECTROLYTE : - The blue colour of the copper chloride solution in the cellappears to fade out over a period of about 15 minutes. The reddish colour acquired by the cathodeis typical copper red colour. Chemical test confirm that it is metallic copper. This tells us thatmetallic copper is deposited at the cathode. Smell and chemical tests of the gas collected at theanode indicate that it is chlorine gas.

Fading of the blue colour of copper chloride solution is indicative of decreasing concentrationof the solution with the passage of electric current through it. It means that copper is formed atthe cathode and chlorine is formed at anode by decomposition of copper chloride.

Thus, electrolysis of aqueous copper chloride using carbon electrodes results in deposition of copper atthe cathode and evolution of chlorine at the anode.

7. ELECTROPLATING

Electroplating is a process in which an object made up of a conducting material, is coated with lessactive metal using electrolysis technique.

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T HE PROCESS : - Surface of the article to be electroplated is cleaned. An electrolytic cell is constructed as follows.1. The article to be electroplated is used as cathode.2. A rod or a plate of the less active metal to be coated on the article is used as anode.3. These electrodes are immersed in a solution of an electrolyte having cations of the same metal

which is used as anode.4. An electric current is passed through the electrolyte for a designated (chosen) period of time.5. The article used as cathode, gets coated with metal used as anode.

USES : - Electroplating is done for two purposes.1. To protect objects of reactive metals from corrosion. E.g. iron or steel articles are electroplated with

chromium or nickel to prevent rusting.2. To improve the look of the object. E.g. Brass article are electroplated with silver to make them more

attractive. Electroplating of silver ornaments with gold (gliding) elevates their rich appearance.

8. ANODISING T ECHNIQUE Anodising technique is one of the applications of electrolysis .

1. This technique is used to make the aluminium surface resistant to corrosion and abrasion.2. In this technique aluminium article is used as an anode. Electrolyte used is dilute sulphuric acid.3. The anode reaction results in formation of a black coloured thin film of aluminium oxide on the

surface of aluminium anode.4. Kitchen articles like anodised pressure cooker, anodised pan are applications of anodising

technique, anodised name plates are another very popular application.5. By putting appropriate dyes in the electrolytic bath coloured surface with decorative finish can be

achieved. This finds applications in gift articles, home appliances and architectural decoration.

9. E LECTROLYTIC CELL

Decomposition of an electrolyte, by passage of electric current through it, is called electrolysis. The process of electrolysis takes place in an electrolytic cell.An arrangement in which cathode and anode are in contact with an electrolyte (placed in a vessel) so as to passelectric current through it is called an electrolytic cell.In the above diagram, the beaker holding an electrolyte and two electrodes is an electrolytic cell.An electrolyte is a substance whose aqueous solution can conduct electric current. The points at which electriccurrent enters or leaves an electrolyte are called electrodes.Electrodes are connected to the terminals of a source of electric power (like a battery). The electrode connectedto the positive terminal of a battery is called anode, while that connected to the negative terminal is calledcathode. Cathode is that electrode at which electrons enter the electrolyte while anode is that electrode at whichelectrons leave the electrolyte. Metal plates, metal rods and carbon rods are some examples of commonly usedelectrodes.

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10 . E XPLAIN NEUTRALISATION REACTION NEUTRALISATION REACTION : - Acids and bases in their aqueous solutions react with each other andproduce salt and water. The resulting solution is neither acidic nor basic but is neutral. This reactionis known as neutralisation reaction. For example

11. STATE THE TYPES OF SOLUTIONS AND GIVE ONE EXAMPLE OF EACH . There are give types of solutions, they are as follows.

i. SOLID IN LIQUID : - In this type, solute is solid and solvent is liquid. Solution exists in liquidstate. Example: Salt of sugar in water, Copper in mercury, sea water etc.

ii. G AS IN L IQUID : - In this type, solute is gas and solvent is liquid, solution exists in liquid state.Example: Carbon dioxide gas dissolved in water i.e. soda water.

iii. G AS IN G AS : - In this type, the solute and solvent both are gases. Solution exists in gaseous state. Ex:Air .

iv. L IQUID IN L IQUID : - In this type, the solute and solvent both are liquids. Solution exists in liquidstate. Example: Alcohol and water.

v. SOLID IN SOLID : - In this type, the solute and solvent both are solids. Solution exists in solidstate. Example Alloy of copper, iron etc.

12. O BTAIN AN EXPRESSION FOR EQUIVALENT RESISTANCE OF THREE RESISTANCESCONNECTED IN SERIES COMBINATION .

If the number of resistance are connected one after another in such a way that the same currentflows through each resistance, then the arrangement is called resistance in series.

1. LetR 1, R2 and R 3 be three resistances connected in a series combination and let R be theirequivalent resistance.

Let V 1, V2 and V 3 be the P.D. across resistances R 1, R2 and R 3 respectively .Let V be the P.D. of the cell.Let I be the current flow through each resistance.

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2. ACCORDING TO O HM S L AW ,

Conclusion Therefore, equivalent resistance in series is equal to the sum of the individual resistances.

13. O BTAIN AN EXPRESSION FOR EQUIVALENT RESISTANCE OF THREE RESISTANCES CONNECTED IN PARALLEL COMBINATION .

If the numbers of resistance are connected between two common points, such that the potentialdifference across each resistance is the same, then the arrangement is called resistance in parallel.

Three resistances R 1, R2 and R 3 are connected in parallel between the points A and B. Let R bethe equivalent resistance of the parallel combination.A Cell E, Key K and the ammeters A are also connected with resistances.Let the current passing through R1 be I 1, R2 be I 2, and R 3 be I 3 and that of R be I.

Thus, the reciprocal of the equivalent resistance is equal to the sum of the reciprocal of the individual resistance .

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14. STATE O HM S LAW AND GIVES ITS LIMITATIONS . Ohms Law : - The current ( I ) in a conductor is directly proportional to the potential difference ( V)between its ends, provided the physical state of the conductor remains the same.

15 . W HAT IS THE FUNCTION OF EARTH WIRE ? W HY IT IS NECESSARY TO EARTH METALLIC APPLIANCES ? 1. Most of the electric appliances are provided with three wires connected to a three pin plug.2. One of the wires is connected to live wire in the mains, the other to the neutral wire and the third

one to the earthing wire.3. The earth wire is a wire that carries away the current from the metal body of an appliance into

the earth.4. The end of earth wire is connected to a metallic body deep inside earth.5. When plug of appliances is inserted in socket and current is switched on, the live wire and

neutral wire come in contact with two wires of the appliance while the earth wire comes incontact with the metal body of the appliance.

6. If an electrical appliance is faulty, the live wire comes in contact with the metal body of theappliance and the current flows in the body of that appliance. Thus, if a person touches such anappliance, he will get a shock.

7. By earthing metal appliances, the current flows from the metal body into the earth and there isno danger to the person handling that appliance.

16. M ENTION ANY FOUR APPLICATIONS OF HEATING EFFECT OF ELECTRIC CURRENT . The four applications of heating effect of electric current are1. Electric heater2. Geyser3. Electric iron4. Electric oven

17. E XPLAIN IN DETAIL THE WORKING OF ELECTRIC BELL . DRAW DIAGRAM FROM DIAGRAMSECTION

a. The electric bell consists of an electromagnet, gong, armature (i.e.) soft iron rod, contact screwand spring.

b. When current is passed through the circuit, the Electromagnet acquires magnetism and attracts theiron rod as a result of which the gong is struck by the hammer and the bell rings.

c. At the same time the contact between the contact screw and iron rod is lost and circuit is broken.d. When the current stops the electromagnet losses its magnetisms and the soft iron rod goes to its

original position.As the iron rod touches the contact screw, the circuit is complete the procedure is repeated and thegong is struck again. The bell goes on ringing as long as the switch is closed.

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18. W RITE ANY TWO PRECAUTIONS _

1. W HILE USING ELECTRICAL APPLIANCE : - The two precautions to be taken while using electrical appliances are1. All electrical appliances must be handled only with dry hands.2. Always switch off the current and remove the plug from the socket before cleaning electric

appliances like refrigerator.

2. AGAINST BAD INSULATIONS : - The two precautions to be taken against bad insulation are1. The live wire must always be insulated.2. The live wire even if it is insulated must be replaced periodically i.e. every 3-4 years. But if

it has become exposed, then it must be replaced immediately.

3. A GAINST IMPROPER EARTHING : - The two precautions to be taken against improper earthing are1. A three pin plug must always be used for all metal appliances.2. The earth wire in a 3 pin plug protects a person from the danger of electric shock.

19. S TATE GENERAL PRECAUTION FOR SAFETY WITH RESPECT TO ELECTRICITY .

The following are the general safety precautions that need to be observed while handlingelectrical appliances .

1. Electric boards and sockets should be fixed at a height beyond the reach of children.2. The current must be switched off and the plug must be removed from the socket before

cleaning electric appliances.3. Electrical appliances must be only handled with dry hands.4. Rubber soled footwear must be worn while using electrical appliances.5. Do not touch with bare hands, a person who is stuck to a liver wire. Use a wooden object like

a stick of a chair in order to save him.

20. DESCRIBE O RESTED S EXPERIMENT WITH THE HELP OF DIAGRAMS TO PROVE THAT ELECTRICCURRENT PRODUCES A MAGNETIC FIELD AROUND IT .

Answer.

1. Take a wire AB and stretch it above a compass needle in a direction parallel to the needle, so that the wire is along thenorth - south direction. The wire should be held in this position by supporting it on the non - conducting stands.Connect the wire in series with cell E and tap key K.

2. Press the tap key so that electric current through the wire form A to B. You will notice that the needle is deflected.Release the tap key to cut off the current. You will notice that s soon as the current stops, the needle returns to itsoriginal position.

3. Interchange the connections of the terminals of the cell. Press the tap key. Now the direction of the current in the wireis reversed and the current flows from B to A. You will notice that in this case, the needle is deflected in the oppositedirection. Release the key to stop the current. You will notice that the needle returns to the original direction.

C ONCLUSION : - From the above experiment we conclude that a current carrying conductor produces amagnetic field around it.

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21. MENTION ANY FOUR APPLICATIONS OF MAGNETIC EFFECTS OF ELECTRIC CURRENT .The four applications of magnetic effects of electric current are:

1. Electric generators.2. Radio3. Galvanometer4. Ammeter5. Voltmeter6. Electromagnet.

22. EXPLAIN WITH DIAGRAM THE WORKING OF A BIOGAS PLANT.C ONSTRUCTION

1. Biogas plant consists of a well like structure called as Digester which contains slurry of animal waster and water.

2. The digester is usually constructed well below the ground level.3. There are two pipes joined to the bottom. One is for feeding animal waste, slurry and other for

taking out the used slurry called as sludge which comes out after fermentation.4. A dome shaped structure called Dome with a valve floats over the slurry in the digester and

serves as an outlet for biogas.W ORKING :

1. In a digester the action of an anaerobic micro organism breaks down or decomposes thecomplex compound of biomass in the slurry, in the presence of water.

2. This process takes place within few days and gases like methane, carbon dioxide, hydrogenand hydrogen sulphide are produced.

3. This mixture of gases is supplied to consumer.4. As biogas contains 80% of methane it is excellent fuel and burns without producing smoke.5. The slurry which has lost biogas is called sludge. It is rich in nitrogenous and phosphatic

compounds and can be used as an excellent fertilizer.

23. How energy can be obtained from flowing water? Discuss the problems associated with it.1. Energy of flowing water is utilized to produce electricity at hydroelectric power station. Dams

are constructed to store the water by obstructing flow of water of a river.2. In this process, kinetic energy is converted into potential energy. The water from the top of the

dam is allowed to fall through pipes over the turbine blades at the bottom of dam.3. When water falls on the turbine, potential energy is converted into kinetic energy and turbines

rotate with greater speed.4. Moving turbines rotate the armature of the electric generator to produce electricity. Energy

obtained from flowing water is known as hydroelectric energy.

Problems associated with energy production from flowing water.1. Hydroelectric power plants can be constructed only at a limited number of places.2. When dams are constructed a large land area gets submerged which may cause long term

pollution of rehabilitation.

24. Explain the calorific value of fuels? Why hydrogen and alcohol could be best source of energy in future?Answer. The heat liberated in joule on complete burning of one gram of fuel is expressed as its calorificvalue.1. Calorific value of hydrogen is the highest among the fuels (150kj/kg). Still it is not commonly used as a

fuel due to its highly explosive nature.2. Safer and cheaper methods to use hydrogen as a fuel are being developed by the scientists.3. Ethanol (alcohol) is a bio fuel produced from baggage and other starch material by fermentation. Its

calorific value is 30J/kg. At present ethanol is mixed with petrol and used as auto fuel. Technology isbeing developed to use ethanol as a main fuel.

4. Hence, hydrogen and alcohol could be the best conventional sources of energy in future to cope up withthe energy crisis.

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25. C LASSIFY THE FOLLOWING EXAMPLES INTO POTENTIAL ENERGY AND KINETIC ENERGY .

1. A book kept on a table. 10. A stretched catapult.2. A running train 11. Water stored in a dam3. Wind 12. The explosive mixture in a bomb.4. A bullet fired from a gun 13. A stretched bow5. An arrow released from a stretched bow 14. A compressed spring6. Waterfall 15. Rotating hands of a clock7. A raised hammer 16. Running water8. Sea waves 17. A rotating top9. A wound spring in a watch. 18. A running boy

Many appliances is daily use are based on inter changeability of different forms of energy explain.

1. According to the law of conservation of energy, energy can neither be created nor destroyed.

But it can be transformed from one form to another.2. Many appliances/devices work on this principle. Some examples of inter-changeability of energy from one form to another are as follows.

No. Example From (Energy) To (Energy)1.2.3.4.5.6.7.

Charging of batteryUsing a battery

Broadcasting stationsRadio

Electric fanElectric iron

Hydro electric power station.

ElectricalChemical

SoundElectricalElectricalElectrical

Mechanical

ChemicalElectricalElectrical

SoundMechanical

HeatElectrical

27. State and explain law of conservation of energy using an example.

1. The law of conservation of energy states that Energy can neither be created nor destroyed. It may beconverted from one form to another. The total amount of energy in the universe always remains constant.

2. According to this law, the sum of various energies in the universe remains constant. Hence, if energy islost in one form, then an exactly equal amount of energy will be obtained in another form.

3. Foe instance, KE and PE together make up the total mechanical energy of an object. The sum of KE and PE does not change with time. i.e. the total energy of an isolated system is constant.Hence any decrease in the P.E. of an object will result in an equal increase in the KE of the objectand vice versa.

4. For example if a stone is kept at a height, all its energy is PE while it has no KE. When this stonefalls towards the ground under gravity, then at the instance when it touches the ground, all itsenergy is KE. The magnitude of this KE is equal to the magnitude of the PE of the stone at the height.

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28. Give two examples of inter changeability of different forms of energy.Answer. Energy in one form can be converted into another form. During such transformation,1.whenever energy in one form disappears, and exactly equal amount of energy reappears inanother form. The examples of energy transformation are given below.While charging a battery, electrical energy is converted into chemical energy, which is stored inthe battery. When the battery is connected into an electric circuit the chemical energy is convertedinto electrical energy.2. The explosive mixture in a bomb possesses chemical energy. When the bomb explodes, thischemical energy is converted into various forms such as kinetic energy, heat, light, sound, etc.In thermal poser station, heat energy is converted into electrical energy.

In hydro electric power station, potential energy is converted into electrical energy.In nuclear power station, nuclear energy is converted into electrical energy.The electrical energy can be converted into different forms such as

a. Kinetic energy for e.g. electric trains, electric fans etc.b. Potential energy for e.g. water stored by electric pump at a height.c. Heat energy for e.g. water heater, electric iron, etc.d. Light energy for e.g. electric bulbs, fluorescent tubes etc.e. Sound energy for e.g. electric bell, radio, etc.f. Chemical energy for e.g. electrolysis, electroplating.

29. CAUSES OF NOISE POLLUTION.Ans. Noise is caused by various sources. These sources are classified as internal and external sources.

a. Internal sources: -

1. Playing of transistor, record player and TV in full volume.2. High sound generated by band and rock music.3. Barking of a dog.4. Noise in factory, machines, rotors, compressed air, mining machines, looms, saw mills,

domestic water pumps etc.

b. External sources: -

1. Rattling of cars, motorcycles and trucks.2. Sound generated by loud speakers.3. Whistle of train and siren.4. Roaring of jet planes.

30. W HAT IS NOISE POLLUTION ? DESCRIBE MEASURES TO CONTROL NOISE POLLUTION .

Ans. Noise pollution is unwanted sound dumped into the atmosphere which is usually a mixture of many tones combines together in a non musical manner.

M EASURES TO CONTROL NOISE POLLUTION : -1. Reduction of noise at the source: The noise can be controlled by reducing the amplitude of

source, charging the operating system and replacing old parts or machines.2. Control of transmission path: In this technique the energy transmitted to the receiver is

controlled. This is achieved by increasing the distance between the source and the receiver,careful designing and layout of building and using sound absorbers.

3. By using ear plug and protective caps (or ear muffs) to block the outer ear passage.4. By controlling the exposure to sound.

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31. WHAT ARE THE EFFECTS OF NOISE POLLUTION? (ANY 6 POINTS)Ans. Noise pollution has the following adverse effect.

1. There is a partial loss of hearing (deafness) and interference with understanding, displacementof bones in the middle ear and in organ of corti.

2. Effect on digestive system and the digestive glands in the stomach. It may develop ulcer.3. If affects reproductive system .4. Effect on pregnancy a pregnant woman may suffer adverse effect and foetus may develop defects.5. Psychological effects There is impaired alertness and feeling of stress.6. It causes high B.P . and cardio vascular system is affected with acceleration of heart rate.7. There is interference with a sleep and lack of a sleep causes irritation and appetite loss.8. It also affects brain, nervous system and loss of pain sensation.9. Noise affects human performance in tasks requiring communication skill and thinking.10. Other physiological effects like feeling of vibration in head or headache.

32. What is reflection of sound? Give any three practical applications of the phenomenon.

Ans. When one shouts into a well or inside an empty hall one hears his own sound after sometime.This is known as reflection of sound. Practical applications of reflection of sound.a) Megaphone:

1. A megaphone is used in fairs or at tourist spots to contact a large group of people.2. A megaphone is a horn shaped tube. In such a tube, sound waves are prevented from spreading

out by multiple reflections.3. The sound waves are confined to the air inside the tube.

b) Reflection of sound from curved surface: 1. Sound energy when reflected from the curved surface is more readily audible at a distance.2. This arrangement is used in auditorium. Curved board placed behind the speaker in an

auditorium throw forward the sound waves that otherwise would get lost.3. The board

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